The patch titled
Subject: uprobes: __replace_page() avoid BUG in munlock_vma_page()
has been added to the -mm tree. Its filename is
uprobes-__replace_page-avoid-bug-in-munlock_vma_page.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/uprobes-__replace_page-avoid-bug-in-munlock_vma_page.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/uprobes-__replace_page-avoid-bug-in-munlock_vma_page.patch
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: uprobes: __replace_page() avoid BUG in munlock_vma_page()
syzbot crashed on the VM_BUG_ON_PAGE(PageTail) in munlock_vma_page(), when
called from uprobes __replace_page(). Which of many ways to fix it?
Settled on not calling when PageCompound (since Head and Tail are equals
in this context, PageCompound the usual check in uprobes.c, and the prior
use of FOLL_SPLIT_PMD will have cleared PageMlocked already).
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2008161338360.20413@eggly.anvils
Fixes: 5a52c9df62b4 ("uprobe: use FOLL_SPLIT_PMD instead of FOLL_SPLIT")
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Reviewed-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [5.4+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/events/uprobes.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/events/uprobes.c~uprobes-__replace_page-avoid-bug-in-munlock_vma_page
+++ a/kernel/events/uprobes.c
@@ -205,7 +205,7 @@ static int __replace_page(struct vm_area
try_to_free_swap(old_page);
page_vma_mapped_walk_done(&pvmw);
- if (vma->vm_flags & VM_LOCKED)
+ if ((vma->vm_flags & VM_LOCKED) && !PageCompound(old_page))
munlock_vma_page(old_page);
put_page(old_page);
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
uprobes-__replace_page-avoid-bug-in-munlock_vma_page.patch
khugepaged-adjust-vm_bug_on_mm-in-__khugepaged_enter.patch
