The patch titled
Subject: codetag: debug: handle existing CODETAG_EMPTY in mark_objexts_empty for slabobj_ext
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
codetag-debug-handle-existing-codetag_empty-in-mark_objexts_empty-for-slabobj_ext.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patche…
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Hao Ge <gehao(a)kylinos.cn>
Subject: codetag: debug: handle existing CODETAG_EMPTY in mark_objexts_empty for slabobj_ext
Date: Wed, 29 Oct 2025 09:43:17 +0800
When alloc_slab_obj_exts() fails and then later succeeds in allocating a
slab extension vector, it calls handle_failed_objexts_alloc() to mark all
objects in the vector as empty. As a result all objects in this slab
(slabA) will have their extensions set to CODETAG_EMPTY.
Later on if this slabA is used to allocate a slabobj_ext vector for
another slab (slabB), we end up with the slabB->obj_exts pointing to a
slabobj_ext vector that itself has a non-NULL slabobj_ext equal to
CODETAG_EMPTY. When slabB gets freed, free_slab_obj_exts() is called to
free slabB->obj_exts vector.
free_slab_obj_exts() calls mark_objexts_empty(slabB->obj_exts) which will
generate a warning because it expects slabobj_ext vectors to have a NULL
obj_ext, not CODETAG_EMPTY.
Modify mark_objexts_empty() to skip the warning and setting the obj_ext
value if it's already set to CODETAG_EMPTY.
To quickly detect this WARN, I modified the code
from:WARN_ON(slab_exts[offs].ref.ct) to WARN_ON(slab_exts[offs].ref.ct
== 1);
We then obtained this message:
[21630.898561] ------------[ cut here ]------------
[21630.898596] kernel BUG at mm/slub.c:2050!
[21630.898611] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
[21630.900372] Modules linked in: squashfs isofs vfio_iommu_type1
vhost_vsock vfio vhost_net vmw_vsock_virtio_transport_common vhost tap
vhost_iotlb iommufd vsock binfmt_misc nfsv3 nfs_acl nfs lockd grace
netfs tls rds dns_resolver tun brd overlay ntfs3 exfat btrfs
blake2b_generic xor xor_neon raid6_pq loop sctp ip6_udp_tunnel
udp_tunnel nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib
nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct
nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4
nf_tables rfkill ip_set sunrpc vfat fat joydev sg sch_fq_codel nfnetlink
virtio_gpu sr_mod cdrom drm_client_lib virtio_dma_buf drm_shmem_helper
drm_kms_helper drm ghash_ce backlight virtio_net virtio_blk virtio_scsi
net_failover virtio_console failover virtio_mmio dm_mirror
dm_region_hash dm_log dm_multipath dm_mod fuse i2c_dev virtio_pci
virtio_pci_legacy_dev virtio_pci_modern_dev virtio virtio_ring autofs4
aes_neon_bs aes_ce_blk [last unloaded: hwpoison_inject]
[21630.909177] CPU: 3 UID: 0 PID: 3787 Comm: kylin-process-m Kdump:
loaded Tainted: G�������������� W�������������������� 6.18.0-rc1+ #74 PREEMPT(voluntary)
[21630.910495] Tainted: [W]=WARN
[21630.910867] Hardware name: QEMU KVM Virtual Machine, BIOS unknown
2/2/2022
[21630.911625] pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS
BTYPE=--)
[21630.912392] pc : __free_slab+0x228/0x250
[21630.912868] lr : __free_slab+0x18c/0x250[21630.913334] sp :
ffff8000a02f73e0
[21630.913830] x29: ffff8000a02f73e0 x28: fffffdffc43fc800 x27:
ffff0000c0011c40
[21630.914677] x26: ffff0000c000cac0 x25: ffff00010fe5e5f0 x24:
ffff000102199b40
[21630.915469] x23: 0000000000000003 x22: 0000000000000003 x21:
ffff0000c0011c40
[21630.916259] x20: fffffdffc4086600 x19: fffffdffc43fc800 x18:
0000000000000000
[21630.917048] x17: 0000000000000000 x16: 0000000000000000 x15:
0000000000000000
[21630.917837] x14: 0000000000000000 x13: 0000000000000000 x12:
ffff70001405ee66
[21630.918640] x11: 1ffff0001405ee65 x10: ffff70001405ee65 x9 :
ffff800080a295dc
[21630.919442] x8 : ffff8000a02f7330 x7 : 0000000000000000 x6 :
0000000000003000
[21630.920232] x5 : 0000000024924925 x4 : 0000000000000001 x3 :
0000000000000007
[21630.921021] x2 : 0000000000001b40 x1 : 000000000000001f x0 :
0000000000000001
[21630.921810] Call trace:
[21630.922130]�� __free_slab+0x228/0x250 (P)
[21630.922669]�� free_slab+0x38/0x118
[21630.923079]�� free_to_partial_list+0x1d4/0x340
[21630.923591]�� __slab_free+0x24c/0x348
[21630.924024]�� ___cache_free+0xf0/0x110
[21630.924468]�� qlist_free_all+0x78/0x130
[21630.924922]�� kasan_quarantine_reduce+0x114/0x148
[21630.925525]�� __kasan_slab_alloc+0x7c/0xb0
[21630.926006]�� kmem_cache_alloc_noprof+0x164/0x5c8
[21630.926699]�� __alloc_object+0x44/0x1f8
[21630.927153]�� __create_object+0x34/0xc8
[21630.927604]�� kmemleak_alloc+0xb8/0xd8
[21630.928052]�� kmem_cache_alloc_noprof+0x368/0x5c8
[21630.928606]�� getname_flags.part.0+0xa4/0x610
[21630.929112]�� getname_flags+0x80/0xd8
[21630.929557]�� vfs_fstatat+0xc8/0xe0
[21630.929975]�� __do_sys_newfstatat+0xa0/0x100
[21630.930469]�� __arm64_sys_newfstatat+0x90/0xd8
[21630.931046]�� invoke_syscall+0xd4/0x258
[21630.931685]�� el0_svc_common.constprop.0+0xb4/0x240
[21630.932467]�� do_el0_svc+0x48/0x68
[21630.932972]�� el0_svc+0x40/0xe0
[21630.933472]�� el0t_64_sync_handler+0xa0/0xe8
[21630.934151]�� el0t_64_sync+0x1ac/0x1b0
[21630.934923] Code: aa1803e0 97ffef2b a9446bf9 17ffff9c (d4210000)
[21630.936461] SMP: stopping secondary CPUs
[21630.939550] Starting crashdump kernel...
[21630.940108] Bye!
Link: https://lkml.kernel.org/r/20251029014317.1533488-1-hao.ge@linux.dev
Fixes: 09c46563ff6d ("codetag: debug: introduce OBJEXTS_ALLOC_FAIL to mark failed slab_ext allocations")
Signed-off-by: Hao Ge <gehao(a)kylinos.cn>
Cc: Christoph Lameter (Ampere) <cl(a)gentwo.org>
Cc: David Rientjes <rientjes(a)google.com>
Cc: gehao <gehao(a)kylinos.cn>
Cc: Roman Gushchin <roman.gushchin(a)linux.dev>
Cc: Shakeel Butt <shakeel.butt(a)linux.dev>
Cc: Suren Baghdasaryan <surenb(a)google.com>
Cc: Vlastimil Babka <vbabka(a)suse.cz>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/slub.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
--- a/mm/slub.c~codetag-debug-handle-existing-codetag_empty-in-mark_objexts_empty-for-slabobj_ext
+++ a/mm/slub.c
@@ -2046,7 +2046,11 @@ static inline void mark_objexts_empty(st
if (slab_exts) {
unsigned int offs = obj_to_index(obj_exts_slab->slab_cache,
obj_exts_slab, obj_exts);
- /* codetag should be NULL */
+
+ if (unlikely(is_codetag_empty(&slab_exts[offs].ref)))
+ return;
+
+ /* codetag should be NULL here */
WARN_ON(slab_exts[offs].ref.ct);
set_codetag_empty(&slab_exts[offs].ref);
}
_
Patches currently in -mm which might be from gehao(a)kylinos.cn are
codetag-debug-handle-existing-codetag_empty-in-mark_objexts_empty-for-slabobj_ext.patch
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The patch titled
Subject: mm/mremap: honour writable bit in mremap pte batching
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-mremap-honour-writable-bit-in-mremap-pte-batching.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patche…
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Dev Jain <dev.jain(a)arm.com>
Subject: mm/mremap: honour writable bit in mremap pte batching
Date: Tue, 28 Oct 2025 12:09:52 +0530
Currently mremap folio pte batch ignores the writable bit during figuring
out a set of similar ptes mapping the same folio. Suppose that the first
pte of the batch is writable while the others are not - set_ptes will end
up setting the writable bit on the other ptes, which is a violation of
mremap semantics. Therefore, use FPB_RESPECT_WRITE to check the writable
bit while determining the pte batch.
Link: https://lkml.kernel.org/r/20251028063952.90313-1-dev.jain@arm.com
Signed-off-by: Dev Jain <dev.jain(a)arm.com>
Fixes: f822a9a81a31 ("mm: optimize mremap() by PTE batching")
Reported-by: David Hildenbrand <david(a)redhat.com>
Debugged-by: David Hildenbrand <david(a)redhat.com>
Acked-by: David Hildenbrand <david(a)redhat.com>
Acked-by: Pedro Falcato <pfalcato(a)suse.de>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Cc: Barry Song <baohua(a)kernel.org>
Cc: Jann Horn <jannh(a)google.com>
Cc: Liam Howlett <liam.howlett(a)oracle.com>
Cc: Vlastimil Babka <vbabka(a)suse.cz>
Cc: <stable(a)vger.kernel.org> [6.17+]
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/mremap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/mremap.c~mm-mremap-honour-writable-bit-in-mremap-pte-batching
+++ a/mm/mremap.c
@@ -187,7 +187,7 @@ static int mremap_folio_pte_batch(struct
if (!folio || !folio_test_large(folio))
return 1;
- return folio_pte_batch(folio, ptep, pte, max_nr);
+ return folio_pte_batch_flags(folio, NULL, ptep, &pte, max_nr, FPB_RESPECT_WRITE);
}
static int move_ptes(struct pagetable_move_control *pmc,
_
Patches currently in -mm which might be from dev.jain(a)arm.com are
mm-mremap-honour-writable-bit-in-mremap-pte-batching.patch
The patch titled
Subject: gcov: add support for GCC 15
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
gcov-add-support-for-gcc-15.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patche…
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Peter Oberparleiter <oberpar(a)linux.ibm.com>
Subject: gcov: add support for GCC 15
Date: Tue, 28 Oct 2025 12:51:25 +0100
Using gcov on kernels compiled with GCC 15 results in truncated 16-byte
long .gcda files with no usable data. To fix this, update GCOV_COUNTERS
to match the value defined by GCC 15.
Tested with GCC 14.3.0 and GCC 15.2.0.
Link: https://lkml.kernel.org/r/20251028115125.1319410-1-oberpar@linux.ibm.com
Signed-off-by: Peter Oberparleiter <oberpar(a)linux.ibm.com>
Reported-by: Matthieu Baerts <matttbe(a)kernel.org>
Closes: https://github.com/linux-test-project/lcov/issues/445
Tested-by: Matthieu Baerts <matttbe(a)kernel.org>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
kernel/gcov/gcc_4_7.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/kernel/gcov/gcc_4_7.c~gcov-add-support-for-gcc-15
+++ a/kernel/gcov/gcc_4_7.c
@@ -18,7 +18,9 @@
#include <linux/mm.h>
#include "gcov.h"
-#if (__GNUC__ >= 14)
+#if (__GNUC__ >= 15)
+#define GCOV_COUNTERS 10
+#elif (__GNUC__ >= 14)
#define GCOV_COUNTERS 9
#elif (__GNUC__ >= 10)
#define GCOV_COUNTERS 8
_
Patches currently in -mm which might be from oberpar(a)linux.ibm.com are
gcov-add-support-for-gcc-15.patch
The patch titled
Subject: s390: fix HugeTLB vmemmap optimization crash
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
s390-fix-hugetlb-vmemmap-optimization-crash.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patche…
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Luiz Capitulino <luizcap(a)redhat.com>
Subject: s390: fix HugeTLB vmemmap optimization crash
Date: Tue, 28 Oct 2025 17:15:33 -0400
A reproducible crash occurs when enabling HugeTLB vmemmap optimization
(HVO) on s390. The crash and the proposed fix were worked on an s390 KVM
guest running on an older hypervisor, as I don't have access to an LPAR.
However, the same issue should occur on bare-metal.
Reproducer (it may take a few runs to trigger):
# sysctl vm.hugetlb_optimize_vmemmap=1
# echo 1 > /proc/sys/vm/nr_hugepages
# echo 0 > /proc/sys/vm/nr_hugepages
Crash log:
[ 52.340369] list_del corruption. prev->next should be 000000d382110008, but was 000000d7116d3880. (prev=000000d7116d3910)
[ 52.340420] ------------[ cut here ]------------
[ 52.340424] kernel BUG at lib/list_debug.c:62!
[ 52.340566] monitor event: 0040 ilc:2 [#1]SMP
[ 52.340573] Modules linked in: ctcm fsm qeth ccwgroup zfcp scsi_transport_fc qdio dasd_fba_mod dasd_eckd_mod dasd_mod xfs ghash_s390 prng des_s390 libdes sha3_512_s390 sha3_256_s390 virtio_net virtio_blk net_failover sha_common failover dm_mirror dm_region_hash dm_log dm_mod paes_s390 crypto_engine pkey_cca pkey_ep11 zcrypt pkey_pckmo pkey aes_s390
[ 52.340606] CPU: 1 UID: 0 PID: 1672 Comm: root-rep2 Kdump: loaded Not tainted 6.18.0-rc3 #1 NONE
[ 52.340610] Hardware name: IBM 3931 LA1 400 (KVM/Linux)
[ 52.340611] Krnl PSW : 0704c00180000000 0000015710cda7fe (__list_del_entry_valid_or_report+0xfe/0x128)
[ 52.340619] R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3
[ 52.340622] Krnl GPRS: c0000000ffffefff 0000000100000027 000000000000006d 0000000000000000
[ 52.340623] 000000d7116d35d8 000000d7116d35d0 0000000000000002 000000d7116d39b0
[ 52.340625] 000000d7116d3880 000000d7116d3910 000000d7116d3910 000000d382110008
[ 52.340626] 000003ffac1ccd08 000000d7116d39b0 0000015710cda7fa 000000d7116d37d0
[ 52.340632] Krnl Code: 0000015710cda7ee: c020003e496f larl %r2,00000157114a3acc
0000015710cda7f4: c0e5ffd5280e brasl %r14,000001571077f810
#0000015710cda7fa: af000000 mc 0,0
>0000015710cda7fe: b9040029 lgr %r2,%r9
0000015710cda802: c0e5ffe5e193 brasl %r14,0000015710996b28
0000015710cda808: e34090080004 lg %r4,8(%r9)
0000015710cda80e: b9040059 lgr %r5,%r9
0000015710cda812: b9040038 lgr %r3,%r8
[ 52.340643] Call Trace:
[ 52.340645] [<0000015710cda7fe>] __list_del_entry_valid_or_report+0xfe/0x128
[ 52.340649] ([<0000015710cda7fa>] __list_del_entry_valid_or_report+0xfa/0x128)
[ 52.340652] [<0000015710a30b2e>] hugetlb_vmemmap_restore_folios+0x96/0x138
[ 52.340655] [<0000015710a268ac>] update_and_free_pages_bulk+0x64/0x150
[ 52.340659] [<0000015710a26f8a>] set_max_huge_pages+0x4ca/0x6f0
[ 52.340662] [<0000015710a273ba>] hugetlb_sysctl_handler_common+0xea/0x120
[ 52.340665] [<0000015710a27484>] hugetlb_sysctl_handler+0x44/0x50
[ 52.340667] [<0000015710b53ffa>] proc_sys_call_handler+0x17a/0x280
[ 52.340672] [<0000015710a90968>] vfs_write+0x2c8/0x3a0
[ 52.340676] [<0000015710a90bd2>] ksys_write+0x72/0x100
[ 52.340679] [<00000157111483a8>] __do_syscall+0x150/0x318
[ 52.340682] [<0000015711153a5e>] system_call+0x6e/0x90
[ 52.340684] Last Breaking-Event-Address:
[ 52.340684] [<000001571077f85c>] _printk+0x4c/0x58
[ 52.340690] Kernel panic - not syncing: Fatal exception: panic_on_oops
This issue was introduced by commit f13b83fdd996 ("hugetlb: batch TLB
flushes when freeing vmemmap"). Before that change, the HVO
implementation called flush_tlb_kernel_range() each time a vmemmap PMD
split and remapping was performed. The mentioned commit changed this to
issue a few flush_tlb_all() calls after performing all remappings.
However, on s390, flush_tlb_kernel_range() expands to __tlb_flush_kernel()
while flush_tlb_all() is not implemented. As a result, we went from
flushing the TLB for every remapping to no flushing at all.
This commit fixes this by implementing flush_tlb_all() on s390 as an alias
to __tlb_flush_global(). This should cause a flush on all TLB entries on
all CPUs as expected by the flush_tlb_all() semantics.
Link: https://lkml.kernel.org/r/20251028211533.47694-1-luizcap@redhat.com
Fixes: f13b83fdd996 ("hugetlb: batch TLB flushes when freeing vmemmap")
Signed-off-by: Luiz Capitulino <luizcap(a)redhat.com>
Cc: Alexander Gordeev <agordeev(a)linux.ibm.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar(a)kernel.org>
Cc: Christian Borntraeger <borntraeger(a)linux.ibm.com>
Cc: David Hildenbrand <david(a)redhat.com>
Cc: Gerald Schaefer <gerald.schaefer(a)linux.ibm.com>
Cc: Heiko Carstens <hca(a)linux.ibm.com>
Cc: Joao Martins <joao.m.martins(a)oracle.com>
Cc: Mike Kravetz <mike.kravetz(a)oracle.com>
Cc: Oscar Salvador <osalvador(a)suse.de>
Cc: Vasily Gorbik <gor(a)linux.ibm.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
arch/s390/include/asm/tlbflush.h | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
--- a/arch/s390/include/asm/tlbflush.h~s390-fix-hugetlb-vmemmap-optimization-crash
+++ a/arch/s390/include/asm/tlbflush.h
@@ -103,9 +103,13 @@ static inline void __tlb_flush_mm_lazy(s
* flush_tlb_range functions need to do the flush.
*/
#define flush_tlb() do { } while (0)
-#define flush_tlb_all() do { } while (0)
#define flush_tlb_page(vma, addr) do { } while (0)
+static inline void flush_tlb_all(void)
+{
+ __tlb_flush_global();
+}
+
static inline void flush_tlb_mm(struct mm_struct *mm)
{
__tlb_flush_mm_lazy(mm);
_
Patches currently in -mm which might be from luizcap(a)redhat.com are
s390-fix-hugetlb-vmemmap-optimization-crash.patch
The patch titled
Subject: codetag: debug: handle existing CODETAG_EMPTY in mark_objexts_empty for slabobj_ext
has been added to the -mm mm-new branch. Its filename is
codetag-debug-handle-existing-codetag_empty-in-mark_objexts_empty-for-slabobj_ext.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patche…
This patch will later appear in the mm-new branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews. Please do not hesitate to respond to
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------------------------------------------------------
From: Hao Ge <gehao(a)kylinos.cn>
Subject: codetag: debug: handle existing CODETAG_EMPTY in mark_objexts_empty for slabobj_ext
Date: Mon, 27 Oct 2025 16:52:14 +0800
Even though obj_exts was created with the __GFP_NO_OBJ_EXT flag, objects
in the same slab may have their extensions allocated via
alloc_slab_obj_exts, and handle_failed_objexts_alloc may be called within
alloc_slab_obj_exts to set their codetag to CODETAG_EMPTY.
Therefore, both NULL and CODETAG_EMPTY are valid for the codetag of
slabobj_ext, as we do not need to re-set it to CODETAG_EMPTY if it is
already CODETAG_EMPTY. It also resolves the warning triggered when the
codetag is CODETAG_EMPTY during slab freeing.
This issue also occurred during our memory stress testing.
The possibility of its occurrence should be as follows:
When a slab allocates a slabobj_ext, the slab to which this slabobj_ext
belongs may have already allocated its own slabobj_ext
and called handle_failed_objexts_alloc. That is to say, the codetag of
this slabobj_ext has been set to CODETAG_EMPTY.
To quickly detect this WARN, I modified the code
from:WARN_ON(slab_exts[offs].ref.ct) to WARN_ON(slab_exts[offs].ref.ct
== 1);
We then obtained this message:
[21630.898561] ------------[ cut here ]------------
[21630.898596] kernel BUG at mm/slub.c:2050!
[21630.898611] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
[21630.900372] Modules linked in: squashfs isofs vfio_iommu_type1
vhost_vsock vfio vhost_net vmw_vsock_virtio_transport_common vhost tap
vhost_iotlb iommufd vsock binfmt_misc nfsv3 nfs_acl nfs lockd grace
netfs tls rds dns_resolver tun brd overlay ntfs3 exfat btrfs
blake2b_generic xor xor_neon raid6_pq loop sctp ip6_udp_tunnel
udp_tunnel nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib
nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct
nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4
nf_tables rfkill ip_set sunrpc vfat fat joydev sg sch_fq_codel nfnetlink
virtio_gpu sr_mod cdrom drm_client_lib virtio_dma_buf drm_shmem_helper
drm_kms_helper drm ghash_ce backlight virtio_net virtio_blk virtio_scsi
net_failover virtio_console failover virtio_mmio dm_mirror
dm_region_hash dm_log dm_multipath dm_mod fuse i2c_dev virtio_pci
virtio_pci_legacy_dev virtio_pci_modern_dev virtio virtio_ring autofs4
aes_neon_bs aes_ce_blk [last unloaded: hwpoison_inject]
[21630.909177] CPU: 3 UID: 0 PID: 3787 Comm: kylin-process-m Kdump:
loaded Tainted: G�������������� W�������������������� 6.18.0-rc1+ #74 PREEMPT(voluntary)
[21630.910495] Tainted: [W]=WARN
[21630.910867] Hardware name: QEMU KVM Virtual Machine, BIOS unknown
2/2/2022
[21630.911625] pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS
BTYPE=--)
[21630.912392] pc : __free_slab+0x228/0x250
[21630.912868] lr : __free_slab+0x18c/0x250[21630.913334] sp :
ffff8000a02f73e0
[21630.913830] x29: ffff8000a02f73e0 x28: fffffdffc43fc800 x27:
ffff0000c0011c40
[21630.914677] x26: ffff0000c000cac0 x25: ffff00010fe5e5f0 x24:
ffff000102199b40
[21630.915469] x23: 0000000000000003 x22: 0000000000000003 x21:
ffff0000c0011c40
[21630.916259] x20: fffffdffc4086600 x19: fffffdffc43fc800 x18:
0000000000000000
[21630.917048] x17: 0000000000000000 x16: 0000000000000000 x15:
0000000000000000
[21630.917837] x14: 0000000000000000 x13: 0000000000000000 x12:
ffff70001405ee66
[21630.918640] x11: 1ffff0001405ee65 x10: ffff70001405ee65 x9 :
ffff800080a295dc
[21630.919442] x8 : ffff8000a02f7330 x7 : 0000000000000000 x6 :
0000000000003000
[21630.920232] x5 : 0000000024924925 x4 : 0000000000000001 x3 :
0000000000000007
[21630.921021] x2 : 0000000000001b40 x1 : 000000000000001f x0 :
0000000000000001
[21630.921810] Call trace:
[21630.922130]�� __free_slab+0x228/0x250 (P)
[21630.922669]�� free_slab+0x38/0x118
[21630.923079]�� free_to_partial_list+0x1d4/0x340
[21630.923591]�� __slab_free+0x24c/0x348
[21630.924024]�� ___cache_free+0xf0/0x110
[21630.924468]�� qlist_free_all+0x78/0x130
[21630.924922]�� kasan_quarantine_reduce+0x114/0x148
[21630.925525]�� __kasan_slab_alloc+0x7c/0xb0
[21630.926006]�� kmem_cache_alloc_noprof+0x164/0x5c8
[21630.926699]�� __alloc_object+0x44/0x1f8
[21630.927153]�� __create_object+0x34/0xc8
[21630.927604]�� kmemleak_alloc+0xb8/0xd8
[21630.928052]�� kmem_cache_alloc_noprof+0x368/0x5c8
[21630.928606]�� getname_flags.part.0+0xa4/0x610
[21630.929112]�� getname_flags+0x80/0xd8
[21630.929557]�� vfs_fstatat+0xc8/0xe0
[21630.929975]�� __do_sys_newfstatat+0xa0/0x100
[21630.930469]�� __arm64_sys_newfstatat+0x90/0xd8
[21630.931046]�� invoke_syscall+0xd4/0x258
[21630.931685]�� el0_svc_common.constprop.0+0xb4/0x240
[21630.932467]�� do_el0_svc+0x48/0x68
[21630.932972]�� el0_svc+0x40/0xe0
[21630.933472]�� el0t_64_sync_handler+0xa0/0xe8
[21630.934151]�� el0t_64_sync+0x1ac/0x1b0
[21630.934923] Code: aa1803e0 97ffef2b a9446bf9 17ffff9c (d4210000)
[21630.936461] SMP: stopping secondary CPUs
[21630.939550] Starting crashdump kernel...
[21630.940108] Bye!
Link: https://lkml.kernel.org/r/20251027085214.184672-1-hao.ge@linux.dev
Fixes: 09c46563ff6d ("codetag: debug: introduce OBJEXTS_ALLOC_FAIL to mark failed slab_ext allocations")
Signed-off-by: Hao Ge <gehao(a)kylinos.cn>
Cc: Suren Baghdasaryan <surenb(a)google.com>
Cc: Christoph Lameter (Ampere) <cl(a)gentwo.org>
Cc: David Rientjes <rientjes(a)google.com>
Cc: Roman Gushchin <roman.gushchin(a)linux.dev>
Cc: Shakeel Butt <shakeel.butt(a)linux.dev>
Cc: Vlastimil Babka <vbabka(a)suse.cz>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/slub.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
--- a/mm/slub.c~codetag-debug-handle-existing-codetag_empty-in-mark_objexts_empty-for-slabobj_ext
+++ a/mm/slub.c
@@ -2046,7 +2046,17 @@ static inline void mark_objexts_empty(st
if (slab_exts) {
unsigned int offs = obj_to_index(obj_exts_slab->slab_cache,
obj_exts_slab, obj_exts);
- /* codetag should be NULL */
+
+ /*
+ * codetag should be either NULL or CODETAG_EMPTY.
+ * When the same slab calls handle_failed_objexts_alloc,
+ * it will set us to CODETAG_EMPTY.
+ *
+ * If codetag is already CODETAG_EMPTY, no action is needed here.
+ */
+ if (unlikely(is_codetag_empty(&slab_exts[offs].ref)))
+ return;
+
WARN_ON(slab_exts[offs].ref.ct);
set_codetag_empty(&slab_exts[offs].ref);
}
_
Patches currently in -mm which might be from gehao(a)kylinos.cn are
codetag-debug-handle-existing-codetag_empty-in-mark_objexts_empty-for-slabobj_ext.patch