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authorHugh Dickins <hughd@google.com>2020-08-21 03:42:17 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-21 19:52:53 +0300
commitc17c3dc9d08b9aad9a55a1e53f205187972f448e (patch)
tree845d5502902b8fc632667474e99d7c2b9333b61e
parent71e843295c680898959b22dc877ae3839cc22470 (diff)
downloadlinux-c17c3dc9d08b9aad9a55a1e53f205187972f448e.tar.xz
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). Fixes: 5a52c9df62b4 ("uprobe: use FOLL_SPLIT_PMD instead of FOLL_SPLIT") Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Song Liu <songliubraving@fb.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: <stable@vger.kernel.org> [5.4+] Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2008161338360.20413@eggly.anvils Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/events/uprobes.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 649fd53dc9ad..0e18aaf23a7b 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -205,7 +205,7 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
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);