From: Hugh Dickins hughd@google.com
commit c17c3dc9d08b9aad9a55a1e53f205187972f448e upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/events/uprobes.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -211,7 +211,7 @@ 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);