diff options
author | Al Viro <viro@zeniv.linux.org.uk> | 2018-05-23 22:53:22 -0400 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-06-06 16:44:38 +0200 |
commit | f01d1b571458ebc8ef6311eef27c8a513038975b (patch) | |
tree | 5aa0bf1a73b7af23aeca6828a4cb7a3f242b18b0 | |
parent | d47c9f5c4e3ec194ec98d48ed59979e851cb1daa (diff) |
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
@@ -636,9 +636,8 @@ 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); |