September 2024 - Linux-stable-mirror

FAILED: patch "[PATCH] net: mana: Fix error handling in mana_create_txq/rxq's NAPI" failed to apply to 6.1-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x b6ecc662037694488bfff7c9fd21c405df8411f2 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024090821-winking-crib-3418@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: b6ecc6620376 ("net: mana: Fix error handling in mana_create_txq/rxq's NAPI cleanup") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From b6ecc662037694488bfff7c9fd21c405df8411f2 Mon Sep 17 00:00:00 2001 From: Souradeep Chakrabarti <schakrabarti(a)linux.microsoft.com> Date: Mon, 2 Sep 2024 05:43:47 -0700 Subject: [PATCH] net: mana: Fix error handling in mana_create_txq/rxq's NAPI cleanup Currently napi_disable() gets called during rxq and txq cleanup, even before napi is enabled and hrtimer is initialized. It causes kernel panic. ? page_fault_oops+0x136/0x2b0 ? page_counter_cancel+0x2e/0x80 ? do_user_addr_fault+0x2f2/0x640 ? refill_obj_stock+0xc4/0x110 ? exc_page_fault+0x71/0x160 ? asm_exc_page_fault+0x27/0x30 ? __mmdrop+0x10/0x180 ? __mmdrop+0xec/0x180 ? hrtimer_active+0xd/0x50 hrtimer_try_to_cancel+0x2c/0xf0 hrtimer_cancel+0x15/0x30 napi_disable+0x65/0x90 mana_destroy_rxq+0x4c/0x2f0 mana_create_rxq.isra.0+0x56c/0x6d0 ? mana_uncfg_vport+0x50/0x50 mana_alloc_queues+0x21b/0x320 ? skb_dequeue+0x5f/0x80 Cc: stable(a)vger.kernel.org Fixes: e1b5683ff62e ("net: mana: Move NAPI from EQ to CQ") Signed-off-by: Souradeep Chakrabarti <schakrabarti(a)linux.microsoft.com> Reviewed-by: Haiyang Zhang <haiyangz(a)microsoft.com> Reviewed-by: Shradha Gupta <shradhagupta(a)linux.microsoft.com> Signed-off-by: David S. Miller <davem(a)davemloft.net> diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c index 39f56973746d..3d151700f658 100644 --- a/drivers/net/ethernet/microsoft/mana/mana_en.c +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c @@ -1872,10 +1872,12 @@ static void mana_destroy_txq(struct mana_port_context *apc) for (i = 0; i < apc->num_queues; i++) { napi = &apc->tx_qp[i].tx_cq.napi; - napi_synchronize(napi); - napi_disable(napi); - netif_napi_del(napi); - + if (apc->tx_qp[i].txq.napi_initialized) { + napi_synchronize(napi); + napi_disable(napi); + netif_napi_del(napi); + apc->tx_qp[i].txq.napi_initialized = false; + } mana_destroy_wq_obj(apc, GDMA_SQ, apc->tx_qp[i].tx_object); mana_deinit_cq(apc, &apc->tx_qp[i].tx_cq); @@ -1931,6 +1933,7 @@ static int mana_create_txq(struct mana_port_context *apc, txq->ndev = net; txq->net_txq = netdev_get_tx_queue(net, i); txq->vp_offset = apc->tx_vp_offset; + txq->napi_initialized = false; skb_queue_head_init(&txq->pending_skbs); memset(&spec, 0, sizeof(spec)); @@ -1997,6 +2000,7 @@ static int mana_create_txq(struct mana_port_context *apc, netif_napi_add_tx(net, &cq->napi, mana_poll); napi_enable(&cq->napi); + txq->napi_initialized = true; mana_gd_ring_cq(cq->gdma_cq, SET_ARM_BIT); } @@ -2008,7 +2012,7 @@ static int mana_create_txq(struct mana_port_context *apc, } static void mana_destroy_rxq(struct mana_port_context *apc, - struct mana_rxq *rxq, bool validate_state) + struct mana_rxq *rxq, bool napi_initialized) { struct gdma_context *gc = apc->ac->gdma_dev->gdma_context; @@ -2023,15 +2027,15 @@ static void mana_destroy_rxq(struct mana_port_context *apc, napi = &rxq->rx_cq.napi; - if (validate_state) + if (napi_initialized) { napi_synchronize(napi); - napi_disable(napi); + napi_disable(napi); + netif_napi_del(napi); + } xdp_rxq_info_unreg(&rxq->xdp_rxq); - netif_napi_del(napi); - mana_destroy_wq_obj(apc, GDMA_RQ, rxq->rxobj); mana_deinit_cq(apc, &rxq->rx_cq); diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h index 7caa334f4888..b8a6c7504ee1 100644 --- a/include/net/mana/mana.h +++ b/include/net/mana/mana.h @@ -98,6 +98,8 @@ struct mana_txq { atomic_t pending_sends; + bool napi_initialized; + struct mana_stats_tx stats; };

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FAILED: patch "[PATCH] userfaultfd: fix checks for huge PMDs" failed to apply to 4.19-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y git checkout FETCH_HEAD git cherry-pick -x 71c186efc1b2cf1aeabfeff3b9bd5ac4c5ac14d8 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024090859-delicious-serpent-3635@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^.. Possible dependencies: 71c186efc1b2 ("userfaultfd: fix checks for huge PMDs") dab6e717429e ("mm: Rename pmd_read_atomic()") 024d232ae4fc ("mm: Fix pmd_read_atomic()") fbfdec9989e6 ("x86/mm/pae: Make pmd_t similar to pte_t") bd74fdaea146 ("mm: multi-gen LRU: support page table walks") 018ee47f1489 ("mm: multi-gen LRU: exploit locality in rmap") ac35a4902374 ("mm: multi-gen LRU: minimal implementation") ec1c86b25f4b ("mm: multi-gen LRU: groundwork") f1e1a7be4718 ("mm/vmscan.c: refactor shrink_node()") d3629af59f41 ("mm/vmscan: make the annotations of refaults code at the right place") e9c2dbc8bf71 ("mm/vmscan: define macros for refaults in struct lruvec") 507228044236 ("mm/khugepaged: record SCAN_PMD_MAPPED when scan_pmd() finds hugepage") 6614a3c3164a ("Merge tag 'mm-stable-2022-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 71c186efc1b2cf1aeabfeff3b9bd5ac4c5ac14d8 Mon Sep 17 00:00:00 2001 From: Jann Horn <jannh(a)google.com> Date: Tue, 13 Aug 2024 22:25:21 +0200 Subject: [PATCH] userfaultfd: fix checks for huge PMDs Patch series "userfaultfd: fix races around pmd_trans_huge() check", v2. The pmd_trans_huge() code in mfill_atomic() is wrong in three different ways depending on kernel version: 1. The pmd_trans_huge() check is racy and can lead to a BUG_ON() (if you hit the right two race windows) - I've tested this in a kernel build with some extra mdelay() calls. See the commit message for a description of the race scenario. On older kernels (before 6.5), I think the same bug can even theoretically lead to accessing transhuge page contents as a page table if you hit the right 5 narrow race windows (I haven't tested this case). 2. As pointed out by Qi Zheng, pmd_trans_huge() is not sufficient for detecting PMDs that don't point to page tables. On older kernels (before 6.5), you'd just have to win a single fairly wide race to hit this. I've tested this on 6.1 stable by racing migration (with a mdelay() patched into try_to_migrate()) against UFFDIO_ZEROPAGE - on my x86 VM, that causes a kernel oops in ptlock_ptr(). 3. On newer kernels (>=6.5), for shmem mappings, khugepaged is allowed to yank page tables out from under us (though I haven't tested that), so I think the BUG_ON() checks in mfill_atomic() are just wrong. I decided to write two separate fixes for these (one fix for bugs 1+2, one fix for bug 3), so that the first fix can be backported to kernels affected by bugs 1+2. This patch (of 2): This fixes two issues. I discovered that the following race can occur: mfill_atomic other thread ============ ============ <zap PMD> pmdp_get_lockless() [reads none pmd] <bail if trans_huge> <if none:> <pagefault creates transhuge zeropage> __pte_alloc [no-op] <zap PMD> <bail if pmd_trans_huge(*dst_pmd)> BUG_ON(pmd_none(*dst_pmd)) I have experimentally verified this in a kernel with extra mdelay() calls; the BUG_ON(pmd_none(*dst_pmd)) triggers. On kernels newer than commit 0d940a9b270b ("mm/pgtable: allow pte_offset_map[_lock]() to fail"), this can't lead to anything worse than a BUG_ON(), since the page table access helpers are actually designed to deal with page tables concurrently disappearing; but on older kernels (<=6.4), I think we could probably theoretically race past the two BUG_ON() checks and end up treating a hugepage as a page table. The second issue is that, as Qi Zheng pointed out, there are other types of huge PMDs that pmd_trans_huge() can't catch: devmap PMDs and swap PMDs (in particular, migration PMDs). On <=6.4, this is worse than the first issue: If mfill_atomic() runs on a PMD that contains a migration entry (which just requires winning a single, fairly wide race), it will pass the PMD to pte_offset_map_lock(), which assumes that the PMD points to a page table. Breakage follows: First, the kernel tries to take the PTE lock (which will crash or maybe worse if there is no "struct page" for the address bits in the migration entry PMD - I think at least on X86 there usually is no corresponding "struct page" thanks to the PTE inversion mitigation, amd64 looks different). If that didn't crash, the kernel would next try to write a PTE into what it wrongly thinks is a page table. As part of fixing these issues, get rid of the check for pmd_trans_huge() before __pte_alloc() - that's redundant, we're going to have to check for that after the __pte_alloc() anyway. Backport note: pmdp_get_lockless() is pmd_read_atomic() in older kernels. Link: https://lkml.kernel.org/r/20240813-uffd-thp-flip-fix-v2-0-5efa61078a41@goog… Link: https://lkml.kernel.org/r/20240813-uffd-thp-flip-fix-v2-1-5efa61078a41@goog… Fixes: c1a4de99fada ("userfaultfd: mcopy_atomic|mfill_zeropage: UFFDIO_COPY|UFFDIO_ZEROPAGE preparation") Signed-off-by: Jann Horn <jannh(a)google.com> Acked-by: David Hildenbrand <david(a)redhat.com> Cc: Andrea Arcangeli <aarcange(a)redhat.com> Cc: Hugh Dickins <hughd(a)google.com> Cc: Jann Horn <jannh(a)google.com> Cc: Pavel Emelyanov <xemul(a)virtuozzo.com> Cc: Qi Zheng <zhengqi.arch(a)bytedance.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index e54e5c8907fa..290b2a0d84ac 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -787,21 +787,23 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, } dst_pmdval = pmdp_get_lockless(dst_pmd); - /* - * If the dst_pmd is mapped as THP don't - * override it and just be strict. - */ - if (unlikely(pmd_trans_huge(dst_pmdval))) { - err = -EEXIST; - break; - } if (unlikely(pmd_none(dst_pmdval)) && unlikely(__pte_alloc(dst_mm, dst_pmd))) { err = -ENOMEM; break; } - /* If an huge pmd materialized from under us fail */ - if (unlikely(pmd_trans_huge(*dst_pmd))) { + dst_pmdval = pmdp_get_lockless(dst_pmd); + /* + * If the dst_pmd is THP don't override it and just be strict. + * (This includes the case where the PMD used to be THP and + * changed back to none after __pte_alloc().) + */ + if (unlikely(!pmd_present(dst_pmdval) || pmd_trans_huge(dst_pmdval) || + pmd_devmap(dst_pmdval))) { + err = -EEXIST; + break; + } + if (unlikely(pmd_bad(dst_pmdval))) { err = -EFAULT; break; }

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FAILED: patch "[PATCH] userfaultfd: fix checks for huge PMDs" failed to apply to 5.4-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x 71c186efc1b2cf1aeabfeff3b9bd5ac4c5ac14d8 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024090857-wieldable-pedicure-19b9@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^.. Possible dependencies: 71c186efc1b2 ("userfaultfd: fix checks for huge PMDs") dab6e717429e ("mm: Rename pmd_read_atomic()") 024d232ae4fc ("mm: Fix pmd_read_atomic()") fbfdec9989e6 ("x86/mm/pae: Make pmd_t similar to pte_t") bd74fdaea146 ("mm: multi-gen LRU: support page table walks") 018ee47f1489 ("mm: multi-gen LRU: exploit locality in rmap") ac35a4902374 ("mm: multi-gen LRU: minimal implementation") ec1c86b25f4b ("mm: multi-gen LRU: groundwork") f1e1a7be4718 ("mm/vmscan.c: refactor shrink_node()") d3629af59f41 ("mm/vmscan: make the annotations of refaults code at the right place") e9c2dbc8bf71 ("mm/vmscan: define macros for refaults in struct lruvec") 507228044236 ("mm/khugepaged: record SCAN_PMD_MAPPED when scan_pmd() finds hugepage") 6614a3c3164a ("Merge tag 'mm-stable-2022-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 71c186efc1b2cf1aeabfeff3b9bd5ac4c5ac14d8 Mon Sep 17 00:00:00 2001 From: Jann Horn <jannh(a)google.com> Date: Tue, 13 Aug 2024 22:25:21 +0200 Subject: [PATCH] userfaultfd: fix checks for huge PMDs Patch series "userfaultfd: fix races around pmd_trans_huge() check", v2. The pmd_trans_huge() code in mfill_atomic() is wrong in three different ways depending on kernel version: 1. The pmd_trans_huge() check is racy and can lead to a BUG_ON() (if you hit the right two race windows) - I've tested this in a kernel build with some extra mdelay() calls. See the commit message for a description of the race scenario. On older kernels (before 6.5), I think the same bug can even theoretically lead to accessing transhuge page contents as a page table if you hit the right 5 narrow race windows (I haven't tested this case). 2. As pointed out by Qi Zheng, pmd_trans_huge() is not sufficient for detecting PMDs that don't point to page tables. On older kernels (before 6.5), you'd just have to win a single fairly wide race to hit this. I've tested this on 6.1 stable by racing migration (with a mdelay() patched into try_to_migrate()) against UFFDIO_ZEROPAGE - on my x86 VM, that causes a kernel oops in ptlock_ptr(). 3. On newer kernels (>=6.5), for shmem mappings, khugepaged is allowed to yank page tables out from under us (though I haven't tested that), so I think the BUG_ON() checks in mfill_atomic() are just wrong. I decided to write two separate fixes for these (one fix for bugs 1+2, one fix for bug 3), so that the first fix can be backported to kernels affected by bugs 1+2. This patch (of 2): This fixes two issues. I discovered that the following race can occur: mfill_atomic other thread ============ ============ <zap PMD> pmdp_get_lockless() [reads none pmd] <bail if trans_huge> <if none:> <pagefault creates transhuge zeropage> __pte_alloc [no-op] <zap PMD> <bail if pmd_trans_huge(*dst_pmd)> BUG_ON(pmd_none(*dst_pmd)) I have experimentally verified this in a kernel with extra mdelay() calls; the BUG_ON(pmd_none(*dst_pmd)) triggers. On kernels newer than commit 0d940a9b270b ("mm/pgtable: allow pte_offset_map[_lock]() to fail"), this can't lead to anything worse than a BUG_ON(), since the page table access helpers are actually designed to deal with page tables concurrently disappearing; but on older kernels (<=6.4), I think we could probably theoretically race past the two BUG_ON() checks and end up treating a hugepage as a page table. The second issue is that, as Qi Zheng pointed out, there are other types of huge PMDs that pmd_trans_huge() can't catch: devmap PMDs and swap PMDs (in particular, migration PMDs). On <=6.4, this is worse than the first issue: If mfill_atomic() runs on a PMD that contains a migration entry (which just requires winning a single, fairly wide race), it will pass the PMD to pte_offset_map_lock(), which assumes that the PMD points to a page table. Breakage follows: First, the kernel tries to take the PTE lock (which will crash or maybe worse if there is no "struct page" for the address bits in the migration entry PMD - I think at least on X86 there usually is no corresponding "struct page" thanks to the PTE inversion mitigation, amd64 looks different). If that didn't crash, the kernel would next try to write a PTE into what it wrongly thinks is a page table. As part of fixing these issues, get rid of the check for pmd_trans_huge() before __pte_alloc() - that's redundant, we're going to have to check for that after the __pte_alloc() anyway. Backport note: pmdp_get_lockless() is pmd_read_atomic() in older kernels. Link: https://lkml.kernel.org/r/20240813-uffd-thp-flip-fix-v2-0-5efa61078a41@goog… Link: https://lkml.kernel.org/r/20240813-uffd-thp-flip-fix-v2-1-5efa61078a41@goog… Fixes: c1a4de99fada ("userfaultfd: mcopy_atomic|mfill_zeropage: UFFDIO_COPY|UFFDIO_ZEROPAGE preparation") Signed-off-by: Jann Horn <jannh(a)google.com> Acked-by: David Hildenbrand <david(a)redhat.com> Cc: Andrea Arcangeli <aarcange(a)redhat.com> Cc: Hugh Dickins <hughd(a)google.com> Cc: Jann Horn <jannh(a)google.com> Cc: Pavel Emelyanov <xemul(a)virtuozzo.com> Cc: Qi Zheng <zhengqi.arch(a)bytedance.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index e54e5c8907fa..290b2a0d84ac 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -787,21 +787,23 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, } dst_pmdval = pmdp_get_lockless(dst_pmd); - /* - * If the dst_pmd is mapped as THP don't - * override it and just be strict. - */ - if (unlikely(pmd_trans_huge(dst_pmdval))) { - err = -EEXIST; - break; - } if (unlikely(pmd_none(dst_pmdval)) && unlikely(__pte_alloc(dst_mm, dst_pmd))) { err = -ENOMEM; break; } - /* If an huge pmd materialized from under us fail */ - if (unlikely(pmd_trans_huge(*dst_pmd))) { + dst_pmdval = pmdp_get_lockless(dst_pmd); + /* + * If the dst_pmd is THP don't override it and just be strict. + * (This includes the case where the PMD used to be THP and + * changed back to none after __pte_alloc().) + */ + if (unlikely(!pmd_present(dst_pmdval) || pmd_trans_huge(dst_pmdval) || + pmd_devmap(dst_pmdval))) { + err = -EEXIST; + break; + } + if (unlikely(pmd_bad(dst_pmdval))) { err = -EFAULT; break; }

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FAILED: patch "[PATCH] userfaultfd: fix checks for huge PMDs" failed to apply to 5.10-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y git checkout FETCH_HEAD git cherry-pick -x 71c186efc1b2cf1aeabfeff3b9bd5ac4c5ac14d8 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024090855-kiln-shrank-fea8@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^.. Possible dependencies: 71c186efc1b2 ("userfaultfd: fix checks for huge PMDs") dab6e717429e ("mm: Rename pmd_read_atomic()") 024d232ae4fc ("mm: Fix pmd_read_atomic()") fbfdec9989e6 ("x86/mm/pae: Make pmd_t similar to pte_t") bd74fdaea146 ("mm: multi-gen LRU: support page table walks") 018ee47f1489 ("mm: multi-gen LRU: exploit locality in rmap") ac35a4902374 ("mm: multi-gen LRU: minimal implementation") ec1c86b25f4b ("mm: multi-gen LRU: groundwork") f1e1a7be4718 ("mm/vmscan.c: refactor shrink_node()") d3629af59f41 ("mm/vmscan: make the annotations of refaults code at the right place") e9c2dbc8bf71 ("mm/vmscan: define macros for refaults in struct lruvec") 507228044236 ("mm/khugepaged: record SCAN_PMD_MAPPED when scan_pmd() finds hugepage") 6614a3c3164a ("Merge tag 'mm-stable-2022-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 71c186efc1b2cf1aeabfeff3b9bd5ac4c5ac14d8 Mon Sep 17 00:00:00 2001 From: Jann Horn <jannh(a)google.com> Date: Tue, 13 Aug 2024 22:25:21 +0200 Subject: [PATCH] userfaultfd: fix checks for huge PMDs Patch series "userfaultfd: fix races around pmd_trans_huge() check", v2. The pmd_trans_huge() code in mfill_atomic() is wrong in three different ways depending on kernel version: 1. The pmd_trans_huge() check is racy and can lead to a BUG_ON() (if you hit the right two race windows) - I've tested this in a kernel build with some extra mdelay() calls. See the commit message for a description of the race scenario. On older kernels (before 6.5), I think the same bug can even theoretically lead to accessing transhuge page contents as a page table if you hit the right 5 narrow race windows (I haven't tested this case). 2. As pointed out by Qi Zheng, pmd_trans_huge() is not sufficient for detecting PMDs that don't point to page tables. On older kernels (before 6.5), you'd just have to win a single fairly wide race to hit this. I've tested this on 6.1 stable by racing migration (with a mdelay() patched into try_to_migrate()) against UFFDIO_ZEROPAGE - on my x86 VM, that causes a kernel oops in ptlock_ptr(). 3. On newer kernels (>=6.5), for shmem mappings, khugepaged is allowed to yank page tables out from under us (though I haven't tested that), so I think the BUG_ON() checks in mfill_atomic() are just wrong. I decided to write two separate fixes for these (one fix for bugs 1+2, one fix for bug 3), so that the first fix can be backported to kernels affected by bugs 1+2. This patch (of 2): This fixes two issues. I discovered that the following race can occur: mfill_atomic other thread ============ ============ <zap PMD> pmdp_get_lockless() [reads none pmd] <bail if trans_huge> <if none:> <pagefault creates transhuge zeropage> __pte_alloc [no-op] <zap PMD> <bail if pmd_trans_huge(*dst_pmd)> BUG_ON(pmd_none(*dst_pmd)) I have experimentally verified this in a kernel with extra mdelay() calls; the BUG_ON(pmd_none(*dst_pmd)) triggers. On kernels newer than commit 0d940a9b270b ("mm/pgtable: allow pte_offset_map[_lock]() to fail"), this can't lead to anything worse than a BUG_ON(), since the page table access helpers are actually designed to deal with page tables concurrently disappearing; but on older kernels (<=6.4), I think we could probably theoretically race past the two BUG_ON() checks and end up treating a hugepage as a page table. The second issue is that, as Qi Zheng pointed out, there are other types of huge PMDs that pmd_trans_huge() can't catch: devmap PMDs and swap PMDs (in particular, migration PMDs). On <=6.4, this is worse than the first issue: If mfill_atomic() runs on a PMD that contains a migration entry (which just requires winning a single, fairly wide race), it will pass the PMD to pte_offset_map_lock(), which assumes that the PMD points to a page table. Breakage follows: First, the kernel tries to take the PTE lock (which will crash or maybe worse if there is no "struct page" for the address bits in the migration entry PMD - I think at least on X86 there usually is no corresponding "struct page" thanks to the PTE inversion mitigation, amd64 looks different). If that didn't crash, the kernel would next try to write a PTE into what it wrongly thinks is a page table. As part of fixing these issues, get rid of the check for pmd_trans_huge() before __pte_alloc() - that's redundant, we're going to have to check for that after the __pte_alloc() anyway. Backport note: pmdp_get_lockless() is pmd_read_atomic() in older kernels. Link: https://lkml.kernel.org/r/20240813-uffd-thp-flip-fix-v2-0-5efa61078a41@goog… Link: https://lkml.kernel.org/r/20240813-uffd-thp-flip-fix-v2-1-5efa61078a41@goog… Fixes: c1a4de99fada ("userfaultfd: mcopy_atomic|mfill_zeropage: UFFDIO_COPY|UFFDIO_ZEROPAGE preparation") Signed-off-by: Jann Horn <jannh(a)google.com> Acked-by: David Hildenbrand <david(a)redhat.com> Cc: Andrea Arcangeli <aarcange(a)redhat.com> Cc: Hugh Dickins <hughd(a)google.com> Cc: Jann Horn <jannh(a)google.com> Cc: Pavel Emelyanov <xemul(a)virtuozzo.com> Cc: Qi Zheng <zhengqi.arch(a)bytedance.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index e54e5c8907fa..290b2a0d84ac 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -787,21 +787,23 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, } dst_pmdval = pmdp_get_lockless(dst_pmd); - /* - * If the dst_pmd is mapped as THP don't - * override it and just be strict. - */ - if (unlikely(pmd_trans_huge(dst_pmdval))) { - err = -EEXIST; - break; - } if (unlikely(pmd_none(dst_pmdval)) && unlikely(__pte_alloc(dst_mm, dst_pmd))) { err = -ENOMEM; break; } - /* If an huge pmd materialized from under us fail */ - if (unlikely(pmd_trans_huge(*dst_pmd))) { + dst_pmdval = pmdp_get_lockless(dst_pmd); + /* + * If the dst_pmd is THP don't override it and just be strict. + * (This includes the case where the PMD used to be THP and + * changed back to none after __pte_alloc().) + */ + if (unlikely(!pmd_present(dst_pmdval) || pmd_trans_huge(dst_pmdval) || + pmd_devmap(dst_pmdval))) { + err = -EEXIST; + break; + } + if (unlikely(pmd_bad(dst_pmdval))) { err = -EFAULT; break; }

1 month, 1 week

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FAILED: patch "[PATCH] userfaultfd: fix checks for huge PMDs" failed to apply to 5.15-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 71c186efc1b2cf1aeabfeff3b9bd5ac4c5ac14d8 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024090853-unworldly-aerobics-75a0@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: 71c186efc1b2 ("userfaultfd: fix checks for huge PMDs") dab6e717429e ("mm: Rename pmd_read_atomic()") 024d232ae4fc ("mm: Fix pmd_read_atomic()") fbfdec9989e6 ("x86/mm/pae: Make pmd_t similar to pte_t") bd74fdaea146 ("mm: multi-gen LRU: support page table walks") 018ee47f1489 ("mm: multi-gen LRU: exploit locality in rmap") ac35a4902374 ("mm: multi-gen LRU: minimal implementation") ec1c86b25f4b ("mm: multi-gen LRU: groundwork") f1e1a7be4718 ("mm/vmscan.c: refactor shrink_node()") d3629af59f41 ("mm/vmscan: make the annotations of refaults code at the right place") e9c2dbc8bf71 ("mm/vmscan: define macros for refaults in struct lruvec") 507228044236 ("mm/khugepaged: record SCAN_PMD_MAPPED when scan_pmd() finds hugepage") 6614a3c3164a ("Merge tag 'mm-stable-2022-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 71c186efc1b2cf1aeabfeff3b9bd5ac4c5ac14d8 Mon Sep 17 00:00:00 2001 From: Jann Horn <jannh(a)google.com> Date: Tue, 13 Aug 2024 22:25:21 +0200 Subject: [PATCH] userfaultfd: fix checks for huge PMDs Patch series "userfaultfd: fix races around pmd_trans_huge() check", v2. The pmd_trans_huge() code in mfill_atomic() is wrong in three different ways depending on kernel version: 1. The pmd_trans_huge() check is racy and can lead to a BUG_ON() (if you hit the right two race windows) - I've tested this in a kernel build with some extra mdelay() calls. See the commit message for a description of the race scenario. On older kernels (before 6.5), I think the same bug can even theoretically lead to accessing transhuge page contents as a page table if you hit the right 5 narrow race windows (I haven't tested this case). 2. As pointed out by Qi Zheng, pmd_trans_huge() is not sufficient for detecting PMDs that don't point to page tables. On older kernels (before 6.5), you'd just have to win a single fairly wide race to hit this. I've tested this on 6.1 stable by racing migration (with a mdelay() patched into try_to_migrate()) against UFFDIO_ZEROPAGE - on my x86 VM, that causes a kernel oops in ptlock_ptr(). 3. On newer kernels (>=6.5), for shmem mappings, khugepaged is allowed to yank page tables out from under us (though I haven't tested that), so I think the BUG_ON() checks in mfill_atomic() are just wrong. I decided to write two separate fixes for these (one fix for bugs 1+2, one fix for bug 3), so that the first fix can be backported to kernels affected by bugs 1+2. This patch (of 2): This fixes two issues. I discovered that the following race can occur: mfill_atomic other thread ============ ============ <zap PMD> pmdp_get_lockless() [reads none pmd] <bail if trans_huge> <if none:> <pagefault creates transhuge zeropage> __pte_alloc [no-op] <zap PMD> <bail if pmd_trans_huge(*dst_pmd)> BUG_ON(pmd_none(*dst_pmd)) I have experimentally verified this in a kernel with extra mdelay() calls; the BUG_ON(pmd_none(*dst_pmd)) triggers. On kernels newer than commit 0d940a9b270b ("mm/pgtable: allow pte_offset_map[_lock]() to fail"), this can't lead to anything worse than a BUG_ON(), since the page table access helpers are actually designed to deal with page tables concurrently disappearing; but on older kernels (<=6.4), I think we could probably theoretically race past the two BUG_ON() checks and end up treating a hugepage as a page table. The second issue is that, as Qi Zheng pointed out, there are other types of huge PMDs that pmd_trans_huge() can't catch: devmap PMDs and swap PMDs (in particular, migration PMDs). On <=6.4, this is worse than the first issue: If mfill_atomic() runs on a PMD that contains a migration entry (which just requires winning a single, fairly wide race), it will pass the PMD to pte_offset_map_lock(), which assumes that the PMD points to a page table. Breakage follows: First, the kernel tries to take the PTE lock (which will crash or maybe worse if there is no "struct page" for the address bits in the migration entry PMD - I think at least on X86 there usually is no corresponding "struct page" thanks to the PTE inversion mitigation, amd64 looks different). If that didn't crash, the kernel would next try to write a PTE into what it wrongly thinks is a page table. As part of fixing these issues, get rid of the check for pmd_trans_huge() before __pte_alloc() - that's redundant, we're going to have to check for that after the __pte_alloc() anyway. Backport note: pmdp_get_lockless() is pmd_read_atomic() in older kernels. Link: https://lkml.kernel.org/r/20240813-uffd-thp-flip-fix-v2-0-5efa61078a41@goog… Link: https://lkml.kernel.org/r/20240813-uffd-thp-flip-fix-v2-1-5efa61078a41@goog… Fixes: c1a4de99fada ("userfaultfd: mcopy_atomic|mfill_zeropage: UFFDIO_COPY|UFFDIO_ZEROPAGE preparation") Signed-off-by: Jann Horn <jannh(a)google.com> Acked-by: David Hildenbrand <david(a)redhat.com> Cc: Andrea Arcangeli <aarcange(a)redhat.com> Cc: Hugh Dickins <hughd(a)google.com> Cc: Jann Horn <jannh(a)google.com> Cc: Pavel Emelyanov <xemul(a)virtuozzo.com> Cc: Qi Zheng <zhengqi.arch(a)bytedance.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index e54e5c8907fa..290b2a0d84ac 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -787,21 +787,23 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, } dst_pmdval = pmdp_get_lockless(dst_pmd); - /* - * If the dst_pmd is mapped as THP don't - * override it and just be strict. - */ - if (unlikely(pmd_trans_huge(dst_pmdval))) { - err = -EEXIST; - break; - } if (unlikely(pmd_none(dst_pmdval)) && unlikely(__pte_alloc(dst_mm, dst_pmd))) { err = -ENOMEM; break; } - /* If an huge pmd materialized from under us fail */ - if (unlikely(pmd_trans_huge(*dst_pmd))) { + dst_pmdval = pmdp_get_lockless(dst_pmd); + /* + * If the dst_pmd is THP don't override it and just be strict. + * (This includes the case where the PMD used to be THP and + * changed back to none after __pte_alloc().) + */ + if (unlikely(!pmd_present(dst_pmdval) || pmd_trans_huge(dst_pmdval) || + pmd_devmap(dst_pmdval))) { + err = -EEXIST; + break; + } + if (unlikely(pmd_bad(dst_pmdval))) { err = -EFAULT; break; }

1 month, 1 week

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FAILED: patch "[PATCH] userfaultfd: fix checks for huge PMDs" failed to apply to 6.1-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 71c186efc1b2cf1aeabfeff3b9bd5ac4c5ac14d8 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024090851-swinging-pug-fba8@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: 71c186efc1b2 ("userfaultfd: fix checks for huge PMDs") dab6e717429e ("mm: Rename pmd_read_atomic()") 024d232ae4fc ("mm: Fix pmd_read_atomic()") fbfdec9989e6 ("x86/mm/pae: Make pmd_t similar to pte_t") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 71c186efc1b2cf1aeabfeff3b9bd5ac4c5ac14d8 Mon Sep 17 00:00:00 2001 From: Jann Horn <jannh(a)google.com> Date: Tue, 13 Aug 2024 22:25:21 +0200 Subject: [PATCH] userfaultfd: fix checks for huge PMDs Patch series "userfaultfd: fix races around pmd_trans_huge() check", v2. The pmd_trans_huge() code in mfill_atomic() is wrong in three different ways depending on kernel version: 1. The pmd_trans_huge() check is racy and can lead to a BUG_ON() (if you hit the right two race windows) - I've tested this in a kernel build with some extra mdelay() calls. See the commit message for a description of the race scenario. On older kernels (before 6.5), I think the same bug can even theoretically lead to accessing transhuge page contents as a page table if you hit the right 5 narrow race windows (I haven't tested this case). 2. As pointed out by Qi Zheng, pmd_trans_huge() is not sufficient for detecting PMDs that don't point to page tables. On older kernels (before 6.5), you'd just have to win a single fairly wide race to hit this. I've tested this on 6.1 stable by racing migration (with a mdelay() patched into try_to_migrate()) against UFFDIO_ZEROPAGE - on my x86 VM, that causes a kernel oops in ptlock_ptr(). 3. On newer kernels (>=6.5), for shmem mappings, khugepaged is allowed to yank page tables out from under us (though I haven't tested that), so I think the BUG_ON() checks in mfill_atomic() are just wrong. I decided to write two separate fixes for these (one fix for bugs 1+2, one fix for bug 3), so that the first fix can be backported to kernels affected by bugs 1+2. This patch (of 2): This fixes two issues. I discovered that the following race can occur: mfill_atomic other thread ============ ============ <zap PMD> pmdp_get_lockless() [reads none pmd] <bail if trans_huge> <if none:> <pagefault creates transhuge zeropage> __pte_alloc [no-op] <zap PMD> <bail if pmd_trans_huge(*dst_pmd)> BUG_ON(pmd_none(*dst_pmd)) I have experimentally verified this in a kernel with extra mdelay() calls; the BUG_ON(pmd_none(*dst_pmd)) triggers. On kernels newer than commit 0d940a9b270b ("mm/pgtable: allow pte_offset_map[_lock]() to fail"), this can't lead to anything worse than a BUG_ON(), since the page table access helpers are actually designed to deal with page tables concurrently disappearing; but on older kernels (<=6.4), I think we could probably theoretically race past the two BUG_ON() checks and end up treating a hugepage as a page table. The second issue is that, as Qi Zheng pointed out, there are other types of huge PMDs that pmd_trans_huge() can't catch: devmap PMDs and swap PMDs (in particular, migration PMDs). On <=6.4, this is worse than the first issue: If mfill_atomic() runs on a PMD that contains a migration entry (which just requires winning a single, fairly wide race), it will pass the PMD to pte_offset_map_lock(), which assumes that the PMD points to a page table. Breakage follows: First, the kernel tries to take the PTE lock (which will crash or maybe worse if there is no "struct page" for the address bits in the migration entry PMD - I think at least on X86 there usually is no corresponding "struct page" thanks to the PTE inversion mitigation, amd64 looks different). If that didn't crash, the kernel would next try to write a PTE into what it wrongly thinks is a page table. As part of fixing these issues, get rid of the check for pmd_trans_huge() before __pte_alloc() - that's redundant, we're going to have to check for that after the __pte_alloc() anyway. Backport note: pmdp_get_lockless() is pmd_read_atomic() in older kernels. Link: https://lkml.kernel.org/r/20240813-uffd-thp-flip-fix-v2-0-5efa61078a41@goog… Link: https://lkml.kernel.org/r/20240813-uffd-thp-flip-fix-v2-1-5efa61078a41@goog… Fixes: c1a4de99fada ("userfaultfd: mcopy_atomic|mfill_zeropage: UFFDIO_COPY|UFFDIO_ZEROPAGE preparation") Signed-off-by: Jann Horn <jannh(a)google.com> Acked-by: David Hildenbrand <david(a)redhat.com> Cc: Andrea Arcangeli <aarcange(a)redhat.com> Cc: Hugh Dickins <hughd(a)google.com> Cc: Jann Horn <jannh(a)google.com> Cc: Pavel Emelyanov <xemul(a)virtuozzo.com> Cc: Qi Zheng <zhengqi.arch(a)bytedance.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index e54e5c8907fa..290b2a0d84ac 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -787,21 +787,23 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, } dst_pmdval = pmdp_get_lockless(dst_pmd); - /* - * If the dst_pmd is mapped as THP don't - * override it and just be strict. - */ - if (unlikely(pmd_trans_huge(dst_pmdval))) { - err = -EEXIST; - break; - } if (unlikely(pmd_none(dst_pmdval)) && unlikely(__pte_alloc(dst_mm, dst_pmd))) { err = -ENOMEM; break; } - /* If an huge pmd materialized from under us fail */ - if (unlikely(pmd_trans_huge(*dst_pmd))) { + dst_pmdval = pmdp_get_lockless(dst_pmd); + /* + * If the dst_pmd is THP don't override it and just be strict. + * (This includes the case where the PMD used to be THP and + * changed back to none after __pte_alloc().) + */ + if (unlikely(!pmd_present(dst_pmdval) || pmd_trans_huge(dst_pmdval) || + pmd_devmap(dst_pmdval))) { + err = -EEXIST; + break; + } + if (unlikely(pmd_bad(dst_pmdval))) { err = -EFAULT; break; }

1 month, 1 week

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FAILED: patch "[PATCH] tracing: Avoid possible softlockup in tracing_iter_reset()" failed to apply to 4.19-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y git checkout FETCH_HEAD git cherry-pick -x 49aa8a1f4d6800721c7971ed383078257f12e8f9 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024090835-matchbox-untreated-40ad@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^.. Possible dependencies: 49aa8a1f4d68 ("tracing: Avoid possible softlockup in tracing_iter_reset()") bc1a72afdc4a ("ring-buffer: Rename ring_buffer_read() to read_buffer_iter_advance()") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 49aa8a1f4d6800721c7971ed383078257f12e8f9 Mon Sep 17 00:00:00 2001 From: Zheng Yejian <zhengyejian(a)huaweicloud.com> Date: Tue, 27 Aug 2024 20:46:54 +0800 Subject: [PATCH] tracing: Avoid possible softlockup in tracing_iter_reset() In __tracing_open(), when max latency tracers took place on the cpu, the time start of its buffer would be updated, then event entries with timestamps being earlier than start of the buffer would be skipped (see tracing_iter_reset()). Softlockup will occur if the kernel is non-preemptible and too many entries were skipped in the loop that reset every cpu buffer, so add cond_resched() to avoid it. Cc: stable(a)vger.kernel.org Fixes: 2f26ebd549b9a ("tracing: use timestamp to determine start of latency traces") Link: https://lore.kernel.org/20240827124654.3817443-1-zhengyejian@huaweicloud.com Suggested-by: Steven Rostedt <rostedt(a)goodmis.org> Signed-off-by: Zheng Yejian <zhengyejian(a)huaweicloud.com> Signed-off-by: Steven Rostedt (Google) <rostedt(a)goodmis.org> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index ebe7ce2f5f4a..edf6bc817aa1 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3958,6 +3958,8 @@ void tracing_iter_reset(struct trace_iterator *iter, int cpu) break; entries++; ring_buffer_iter_advance(buf_iter); + /* This could be a big loop */ + cond_resched(); } per_cpu_ptr(iter->array_buffer->data, cpu)->skipped_entries = entries;

1 month, 1 week

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FAILED: patch "[PATCH] tracing: Avoid possible softlockup in tracing_iter_reset()" failed to apply to 5.4-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x 49aa8a1f4d6800721c7971ed383078257f12e8f9 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024090834-cheddar-crust-24f3@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^.. Possible dependencies: 49aa8a1f4d68 ("tracing: Avoid possible softlockup in tracing_iter_reset()") bc1a72afdc4a ("ring-buffer: Rename ring_buffer_read() to read_buffer_iter_advance()") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 49aa8a1f4d6800721c7971ed383078257f12e8f9 Mon Sep 17 00:00:00 2001 From: Zheng Yejian <zhengyejian(a)huaweicloud.com> Date: Tue, 27 Aug 2024 20:46:54 +0800 Subject: [PATCH] tracing: Avoid possible softlockup in tracing_iter_reset() In __tracing_open(), when max latency tracers took place on the cpu, the time start of its buffer would be updated, then event entries with timestamps being earlier than start of the buffer would be skipped (see tracing_iter_reset()). Softlockup will occur if the kernel is non-preemptible and too many entries were skipped in the loop that reset every cpu buffer, so add cond_resched() to avoid it. Cc: stable(a)vger.kernel.org Fixes: 2f26ebd549b9a ("tracing: use timestamp to determine start of latency traces") Link: https://lore.kernel.org/20240827124654.3817443-1-zhengyejian@huaweicloud.com Suggested-by: Steven Rostedt <rostedt(a)goodmis.org> Signed-off-by: Zheng Yejian <zhengyejian(a)huaweicloud.com> Signed-off-by: Steven Rostedt (Google) <rostedt(a)goodmis.org> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index ebe7ce2f5f4a..edf6bc817aa1 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3958,6 +3958,8 @@ void tracing_iter_reset(struct trace_iterator *iter, int cpu) break; entries++; ring_buffer_iter_advance(buf_iter); + /* This could be a big loop */ + cond_resched(); } per_cpu_ptr(iter->array_buffer->data, cpu)->skipped_entries = entries;

1 month, 1 week

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FAILED: patch "[PATCH] Revert "mm: skip CMA pages when they are not available"" failed to apply to 6.6-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x bfe0857c20c663fcc1592fa4e3a61ca12b07dac9 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024090830-imaging-symphonic-8783@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: bfe0857c20c6 ("Revert "mm: skip CMA pages when they are not available"") 97144ce008f9 ("mm/vmscan: use folio_migratetype() instead of get_pageblock_migratetype()") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From bfe0857c20c663fcc1592fa4e3a61ca12b07dac9 Mon Sep 17 00:00:00 2001 From: Usama Arif <usamaarif642(a)gmail.com> Date: Wed, 21 Aug 2024 20:26:07 +0100 Subject: [PATCH] Revert "mm: skip CMA pages when they are not available" This reverts commit 5da226dbfce3 ("mm: skip CMA pages when they are not available") and b7108d66318a ("Multi-gen LRU: skip CMA pages when they are not eligible"). lruvec->lru_lock is highly contended and is held when calling isolate_lru_folios. If the lru has a large number of CMA folios consecutively, while the allocation type requested is not MIGRATE_MOVABLE, isolate_lru_folios can hold the lock for a very long time while it skips those. For FIO workload, ~150million order=0 folios were skipped to isolate a few ZONE_DMA folios [1]. This can cause lockups [1] and high memory pressure for extended periods of time [2]. Remove skipping CMA for MGLRU as well, as it was introduced in sort_folio for the same resaon as 5da226dbfce3a2f44978c2c7cf88166e69a6788b. [1] https://lore.kernel.org/all/CAOUHufbkhMZYz20aM_3rHZ3OcK4m2puji2FGpUpn_-DevG… [2] https://lore.kernel.org/all/ZrssOrcJIDy8hacI@gmail.com/ [usamaarif642(a)gmail.com: also revert b7108d66318a, per Johannes] Link: https://lkml.kernel.org/r/9060a32d-b2d7-48c0-8626-1db535653c54@gmail.com Link: https://lkml.kernel.org/r/357ac325-4c61-497a-92a3-bdbd230d5ec9@gmail.com Link: https://lkml.kernel.org/r/9060a32d-b2d7-48c0-8626-1db535653c54@gmail.com Fixes: 5da226dbfce3 ("mm: skip CMA pages when they are not available") Signed-off-by: Usama Arif <usamaarif642(a)gmail.com> Acked-by: Johannes Weiner <hannes(a)cmpxchg.org> Cc: Bharata B Rao <bharata(a)amd.com> Cc: Breno Leitao <leitao(a)debian.org> Cc: David Hildenbrand <david(a)redhat.com> Cc: Matthew Wilcox <willy(a)infradead.org> Cc: Rik van Riel <riel(a)surriel.com> Cc: Vlastimil Babka <vbabka(a)suse.cz> Cc: Yu Zhao <yuzhao(a)google.com> Cc: Zhaoyang Huang <huangzhaoyang(a)gmail.com> Cc: Zhaoyang Huang <zhaoyang.huang(a)unisoc.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/vmscan.c b/mm/vmscan.c index cfa839284b92..bd489c1af228 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1604,25 +1604,6 @@ static __always_inline void update_lru_sizes(struct lruvec *lruvec, } -#ifdef CONFIG_CMA -/* - * It is waste of effort to scan and reclaim CMA pages if it is not available - * for current allocation context. Kswapd can not be enrolled as it can not - * distinguish this scenario by using sc->gfp_mask = GFP_KERNEL - */ -static bool skip_cma(struct folio *folio, struct scan_control *sc) -{ - return !current_is_kswapd() && - gfp_migratetype(sc->gfp_mask) != MIGRATE_MOVABLE && - folio_migratetype(folio) == MIGRATE_CMA; -} -#else -static bool skip_cma(struct folio *folio, struct scan_control *sc) -{ - return false; -} -#endif - /* * Isolating page from the lruvec to fill in @dst list by nr_to_scan times. * @@ -1669,8 +1650,7 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan, nr_pages = folio_nr_pages(folio); total_scan += nr_pages; - if (folio_zonenum(folio) > sc->reclaim_idx || - skip_cma(folio, sc)) { + if (folio_zonenum(folio) > sc->reclaim_idx) { nr_skipped[folio_zonenum(folio)] += nr_pages; move_to = &folios_skipped; goto move; @@ -4320,7 +4300,7 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_c } /* ineligible */ - if (zone > sc->reclaim_idx || skip_cma(folio, sc)) { + if (zone > sc->reclaim_idx) { gen = folio_inc_gen(lruvec, folio, false); list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]); return true;

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FAILED: patch "[PATCH] maple_tree: remove rcu_read_lock() from mt_validate()" failed to apply to 6.1-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x f806de88d8f7f8191afd0fd9b94db4cd058e7d4f # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024090851-coroner-surname-cd39@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: f806de88d8f7 ("maple_tree: remove rcu_read_lock() from mt_validate()") 9a40d45c1f2c ("maple_tree: remove mas_searchable()") 067311d33e65 ("maple_tree: separate ma_state node from status") 271f61a8b41d ("maple_tree: clean up inlines for some functions") bf857ddd21d0 ("maple_tree: move debug check to __mas_set_range()") f7a590189539 ("maple_tree: make mas_erase() more robust") a2587a7e8d37 ("maple_tree: add test for mtree_dup()") fd32e4e9b764 ("maple_tree: introduce interfaces __mt_dup() and mtree_dup()") 4f2267b58a22 ("maple_tree: add mt_free_one() and mt_attr() helpers") a8091f039c1e ("maple_tree: add MAS_UNDERFLOW and MAS_OVERFLOW states") 5c590804b6b0 ("maple_tree: add mas_is_active() to detect in-tree walks") 530f745c7620 ("maple_tree: replace data before marking dead in split and spanning store") 4ffc2ee2cf01 ("maple_tree: introduce mas_tree_parent() definition") 1238f6a226dc ("maple_tree: introduce mas_put_in_tree()") 72bcf4aa86ec ("maple_tree: reorder replacement of nodes to avoid live lock") fec29364348f ("maple_tree: reduce resets during store setup") da0892547b10 ("maple_tree: re-introduce entry to mas_preallocate() arguments") 53bee98d004f ("mm: remove re-walk from mmap_region()") c1297987cc2a ("maple_tree: introduce __mas_set_range()") a489539e33c2 ("maple_tree: update mt_validate()") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From f806de88d8f7f8191afd0fd9b94db4cd058e7d4f Mon Sep 17 00:00:00 2001 From: "Liam R. Howlett" <Liam.Howlett(a)Oracle.com> Date: Tue, 20 Aug 2024 13:54:17 -0400 Subject: [PATCH] maple_tree: remove rcu_read_lock() from mt_validate() The write lock should be held when validating the tree to avoid updates racing with checks. Holding the rcu read lock during a large tree validation may also cause a prolonged rcu read window and "rcu_preempt detected stalls" warnings. Link: https://lore.kernel.org/all/0000000000001d12d4062005aea1@google.com/ Link: https://lkml.kernel.org/r/20240820175417.2782532-1-Liam.Howlett@oracle.com Fixes: 54a611b60590 ("Maple Tree: add new data structure") Signed-off-by: Liam R. Howlett <Liam.Howlett(a)Oracle.com> Reported-by: syzbot+036af2f0c7338a33b0cd(a)syzkaller.appspotmail.com Cc: Hillf Danton <hdanton(a)sina.com> Cc: Matthew Wilcox <willy(a)infradead.org> Cc: "Paul E. McKenney" <paulmck(a)kernel.org> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/lib/maple_tree.c b/lib/maple_tree.c index aa3a5df15b8e..6df3a8b95808 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -7566,14 +7566,14 @@ static void mt_validate_nulls(struct maple_tree *mt) * 2. The gap is correctly set in the parents */ void mt_validate(struct maple_tree *mt) + __must_hold(mas->tree->ma_lock) { unsigned char end; MA_STATE(mas, mt, 0, 0); - rcu_read_lock(); mas_start(&mas); if (!mas_is_active(&mas)) - goto done; + return; while (!mte_is_leaf(mas.node)) mas_descend(&mas); @@ -7594,9 +7594,6 @@ void mt_validate(struct maple_tree *mt) mas_dfs_postorder(&mas, ULONG_MAX); } mt_validate_nulls(mt); -done: - rcu_read_unlock(); - } EXPORT_SYMBOL_GPL(mt_validate);

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