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authorSuren Baghdasaryan <surenb@google.com>2023-07-08 12:12:11 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2023-07-08 14:08:02 -0700
commit33313a747e81af9f31d0d45de78c9397fa3655eb (patch)
tree9e4050107b487128f0b628c7b7117082953e23eb /mm
parentc137381f71aec755fbf47cd4e9bd4dce752c054c (diff)
mm: lock newly mapped VMA which can be modified after it becomes visible
mmap_region adds a newly created VMA into VMA tree and might modify it afterwards before dropping the mmap_lock. This poses a problem for page faults handled under per-VMA locks because they don't take the mmap_lock and can stumble on this VMA while it's still being modified. Currently this does not pose a problem since post-addition modifications are done only for file-backed VMAs, which are not handled under per-VMA lock. However, once support for handling file-backed page faults with per-VMA locks is added, this will become a race. Fix this by write-locking the VMA before inserting it into the VMA tree. Other places where a new VMA is added into VMA tree do not modify it after the insertion, so do not need the same locking. Cc: stable@vger.kernel.org Signed-off-by: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/mmap.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index c66e4622a557..84c71431a527 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2812,6 +2812,8 @@ cannot_expand:
if (vma->vm_file)
i_mmap_lock_write(vma->vm_file->f_mapping);
+ /* Lock the VMA since it is modified after insertion into VMA tree */
+ vma_start_write(vma);
vma_iter_store(&vmi, vma);
mm->map_count++;
if (vma->vm_file) {