Commit c17c3dc9 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds

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: 5a52c9df ("uprobe: use FOLL_SPLIT_PMD instead of FOLL_SPLIT")
Reported-by: default avatarsyzbot <syzkaller@googlegroups.com>
Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Acked-by: default avatarOleg 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.anvilsSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 71e84329
......@@ -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);
......
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