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author | Al Viro <viro@zeniv.linux.org.uk> | 2018-05-24 05:53:22 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-06-05 12:46:14 +0300 |
commit | 3035e187f397edaf81de0d859bff7c6bc26057c8 (patch) | |
tree | 48dcfb8677013f06ecfe0f10e2cb83524059abc2 | |
parent | 698127c59e55ca0cbdab86321d7779945db6f624 (diff) | |
download | linux-3035e187f397edaf81de0d859bff7c6bc26057c8.tar.xz |
fix io_destroy()/aio_complete() race
commit 4faa99965e027cc057c5145ce45fa772caa04e8d upstream.
If io_destroy() gets to cancelling everything that can be cancelled and
gets to kiocb_cancel() calling the function driver has left in ->ki_cancel,
it becomes vulnerable to a race with IO completion. At that point req
is already taken off the list and aio_complete() does *NOT* spin until
we (in free_ioctx_users()) releases ->ctx_lock. As the result, it proceeds
to kiocb_free(), freing req just it gets passed to ->ki_cancel().
Fix is simple - remove from the list after the call of kiocb_cancel(). All
instances of ->ki_cancel() already have to cope with the being called with
iocb still on list - that's what happens in io_cancel(2).
Cc: stable@kernel.org
Fixes: 0460fef2a921 "aio: use cancellation list lazily"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r-- | fs/aio.c | 3 |
1 files changed, 1 insertions, 2 deletions
@@ -643,9 +643,8 @@ static void free_ioctx_users(struct percpu_ref *ref) while (!list_empty(&ctx->active_reqs)) { req = list_first_entry(&ctx->active_reqs, struct aio_kiocb, ki_list); - - list_del_init(&req->ki_list); kiocb_cancel(req); + list_del_init(&req->ki_list); } spin_unlock_irq(&ctx->ctx_lock); |