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authorAl Viro <viro@zeniv.linux.org.uk>2018-05-23 22:53:22 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2018-05-23 22:53:22 -0400
commit4faa99965e027cc057c5145ce45fa772caa04e8d (patch)
tree5c0c1e8d18e1a4f0964fe8b40e343ecd9cfbada8
parentbaf10564fbb66ea222cae66fbff11c444590ffd9 (diff)
fix io_destroy()/aio_complete() race
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>
-rw-r--r--fs/aio.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/fs/aio.c b/fs/aio.c
index 8061d9787e54..49f53516eef0 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -634,9 +634,8 @@ 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);