mm: lock newly mapped VMA which can be modified after it becomes visible

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commit 33313a747e upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

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Suren Baghdasaryan 2023-07-08 12:12:11 -07:00 • committed by Greg Kroah-Hartman

parent 10bef9542a

commit 406815be90

1 changed files with 2 additions and 0 deletions

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mm/mmap.c

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