io_uring/cancel: re-grab ctx mutex after finishing wait

[ Upstream commit 23fffb2f09ce1145cbd751801d45ba74acaa6542 ]

If we have a signal pending during cancelations, it'll cause the
task_work run to return an error. Since we didn't run task_work, the
current task is left in TASK_INTERRUPTIBLE state when we need to
re-grab the ctx mutex, and the kernel will rightfully complain about
that.

Move the lock grabbing for the error cases outside the loop to avoid
that issue.

Reported-by: syzbot+7df055631cd1be4586fd@syzkaller.appspotmail.com
Link: https://lore.kernel.org/io-uring/0000000000003a14a905f05050b0@google.com/
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/io_uring/cancel.c b/io_uring/cancel.c
index 2291a53..b4f5dfa 100644 (file)
--- a/io_uring/cancel.c
+++ b/io_uring/cancel.c
@@ -288,24 +288,23 @@ int io_sync_cancel(struct io_ring_ctx *ctx, void __user *arg)
 
                ret = __io_sync_cancel(current->io_uring, &cd, sc.fd);
 
+               mutex_unlock(&ctx->uring_lock);
                if (ret != -EALREADY)
                        break;
 
-               mutex_unlock(&ctx->uring_lock);
                ret = io_run_task_work_sig(ctx);
-               if (ret < 0) {
-                       mutex_lock(&ctx->uring_lock);
+               if (ret < 0)
                        break;
-               }
                ret = schedule_hrtimeout(&timeout, HRTIMER_MODE_ABS);
-               mutex_lock(&ctx->uring_lock);
                if (!ret) {
                        ret = -ETIME;
                        break;
                }
+               mutex_lock(&ctx->uring_lock);
        } while (1);
 
        finish_wait(&ctx->cq_wait, &wait);
+       mutex_lock(&ctx->uring_lock);
 
        if (ret == -ENOENT || ret > 0)
                ret = 0;