From: Suren Baghdasaryan Date: Mon, 27 Feb 2023 17:36:23 +0000 (-0800) Subject: mm: fall back to mmap_lock if vma->anon_vma is not yet set X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=2ac0af1b66e3b66307f53b1cc446514308ec466d;p=linux.git mm: fall back to mmap_lock if vma->anon_vma is not yet set When vma->anon_vma is not set, page fault handler will set it by either reusing anon_vma of an adjacent VMA if VMAs are compatible or by allocating a new one. find_mergeable_anon_vma() walks VMA tree to find a compatible adjacent VMA and that requires not only the faulting VMA to be stable but also the tree structure and other VMAs inside that tree. Therefore locking just the faulting VMA is not enough for this search. Fall back to taking mmap_lock when vma->anon_vma is not set. This situation happens only on the first page fault and should not affect overall performance. Link: https://lkml.kernel.org/r/20230227173632.3292573-25-surenb@google.com Signed-off-by: Suren Baghdasaryan Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Signed-off-by: Andrew Morton --- diff --git a/mm/memory.c b/mm/memory.c index 1235de20af739..10d497a5296c3 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5254,6 +5254,10 @@ retry: if (!vma_is_anonymous(vma)) goto inval; + /* find_mergeable_anon_vma uses adjacent vmas which are not locked */ + if (!vma->anon_vma) + goto inval; + if (!vma_start_read(vma)) goto inval;