Khugepaged collapse an anonymous thp in two rounds of scans. The 2nd round
done in __collapse_huge_page_isolate() after hpage_collapse_scan_pmd(),
during which all the locks will be released temporarily. It means the
pgtable can change during this phase before 2nd round starts.
It's logically possible some ptes got wr-protected during this phase, and
we can errornously collapse a thp without noticing some ptes are
wr-protected by userfault. e1e267c7928f wanted to avoid it but it only did
that for the 1st phase, not the 2nd phase.
Since __collapse_huge_page_isolate() happens after a round of small page
swapins, we don't need to worry on any !present ptes - if it existed
khugepaged will already bail out. So we only need to check present ptes
with uffd-wp bit set there.
This is something I found only but never had a reproducer, I thought it was
one caused a bug in Muhammad's recent pagemap new ioctl work, but it turns
out it's not the cause of that but an userspace bug. However this seems to
still be a real bug even with a very small race window, still worth to have
it fixed and copy stable.
Cc: linux-stable <stable(a)vger.kernel.org>
Fixes: e1e267c7928f ("khugepaged: skip collapse if uffd-wp detected")
Signed-off-by: Peter Xu <peterx(a)redhat.com>
---
mm/khugepaged.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index a19aa140fd52..42ac93b4bd87 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -575,6 +575,10 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
result = SCAN_PTE_NON_PRESENT;
goto out;
}
+ if (pte_uffd_wp(pteval)) {
+ result = SCAN_PTE_UFFD_WP;
+ goto out;
+ }
page = vm_normal_page(vma, address, pteval);
if (unlikely(!page) || unlikely(is_zone_device_page(page))) {
result = SCAN_PAGE_NULL;
--
2.39.1
This is a note to let you know that I've just added the patch titled
usb: cdnsp: Fixes error: uninitialized symbol 'len'
to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
From 1edf48991a783d00a3a18dc0d27c88139e4030a2 Mon Sep 17 00:00:00 2001
From: Pawel Laszczak <pawell(a)cadence.com>
Date: Fri, 31 Mar 2023 05:06:00 -0400
Subject: usb: cdnsp: Fixes error: uninitialized symbol 'len'
The patch 5bc38d33a5a1: "usb: cdnsp: Fixes issue with redundant
Status Stage" leads to the following Smatch static checker warning:
drivers/usb/cdns3/cdnsp-ep0.c:470 cdnsp_setup_analyze()
error: uninitialized symbol 'len'.
cc: <stable(a)vger.kernel.org>
Fixes: 5bc38d33a5a1 ("usb: cdnsp: Fixes issue with redundant Status Stage")
Signed-off-by: Pawel Laszczak <pawell(a)cadence.com>
Link: https://lore.kernel.org/r/20230331090600.454674-1-pawell@cadence.com
Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>
---
drivers/usb/cdns3/cdnsp-ep0.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/usb/cdns3/cdnsp-ep0.c b/drivers/usb/cdns3/cdnsp-ep0.c
index d63d5d92f255..f317d3c84781 100644
--- a/drivers/usb/cdns3/cdnsp-ep0.c
+++ b/drivers/usb/cdns3/cdnsp-ep0.c
@@ -414,7 +414,7 @@ static int cdnsp_ep0_std_request(struct cdnsp_device *pdev,
void cdnsp_setup_analyze(struct cdnsp_device *pdev)
{
struct usb_ctrlrequest *ctrl = &pdev->setup;
- int ret = 0;
+ int ret = -EINVAL;
u16 len;
trace_cdnsp_ctrl_req(ctrl);
@@ -424,7 +424,6 @@ void cdnsp_setup_analyze(struct cdnsp_device *pdev)
if (pdev->gadget.state == USB_STATE_NOTATTACHED) {
dev_err(pdev->dev, "ERR: Setup detected in unattached state\n");
- ret = -EINVAL;
goto out;
}
--
2.40.0
Looks like what we fixed for hugetlb in commit 44f86392bdd1 ("mm/hugetlb:
fix uffd-wp handling for migration entries in hugetlb_change_protection()")
similarly applies to THP.
Setting/clearing uffd-wp on THP migration entries is not implemented
properly. Further, while removing migration PMDs considers the uffd-wp
bit, inserting migration PMDs does not consider the uffd-wp bit.
We have to set/clear independently of the migration entry type in
change_huge_pmd() and properly copy the uffd-wp bit in
set_pmd_migration_entry().
Verified using a simple reproducer that triggers migration of a THP, that
the set_pmd_migration_entry() no longer loses the uffd-wp bit.
Fixes: f45ec5ff16a7 ("userfaultfd: wp: support swap and page migration")
Reviewed-by: Peter Xu <peterx(a)redhat.com>
Cc: stable(a)vger.kernel.org
Signed-off-by: David Hildenbrand <david(a)redhat.com>
---
mm/huge_memory.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 032fb0ef9cd1..e3706a2b34b2 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1838,10 +1838,10 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
if (is_swap_pmd(*pmd)) {
swp_entry_t entry = pmd_to_swp_entry(*pmd);
struct page *page = pfn_swap_entry_to_page(entry);
+ pmd_t newpmd;
VM_BUG_ON(!is_pmd_migration_entry(*pmd));
if (is_writable_migration_entry(entry)) {
- pmd_t newpmd;
/*
* A protection check is difficult so
* just be safe and disable write
@@ -1855,8 +1855,16 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
newpmd = pmd_swp_mksoft_dirty(newpmd);
if (pmd_swp_uffd_wp(*pmd))
newpmd = pmd_swp_mkuffd_wp(newpmd);
- set_pmd_at(mm, addr, pmd, newpmd);
+ } else {
+ newpmd = *pmd;
}
+
+ if (uffd_wp)
+ newpmd = pmd_swp_mkuffd_wp(newpmd);
+ else if (uffd_wp_resolve)
+ newpmd = pmd_swp_clear_uffd_wp(newpmd);
+ if (!pmd_same(*pmd, newpmd))
+ set_pmd_at(mm, addr, pmd, newpmd);
goto unlock;
}
#endif
@@ -3251,6 +3259,8 @@ int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
pmdswp = swp_entry_to_pmd(entry);
if (pmd_soft_dirty(pmdval))
pmdswp = pmd_swp_mksoft_dirty(pmdswp);
+ if (pmd_uffd_wp(pmdval))
+ pmdswp = pmd_swp_mkuffd_wp(pmdswp);
set_pmd_at(mm, address, pvmw->pmd, pmdswp);
page_remove_rmap(page, vma, true);
put_page(page);
--
2.39.2