Commit d7a6ae40 authored by Jens Axboe's avatar Jens Axboe Committed by Baokun Li
Browse files

io_uring: check if we need to reschedule during overflow flush 

stable inclusion
from stable-v6.6.57
commit f4ce3b5d26ce149e77e6b8e8f2058aa80e5b034e
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYRF9
CVE: CVE-2024-50060

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f4ce3b5d26ce149e77e6b8e8f2058aa80e5b034e

--------------------------------

[ Upstream commit eac2ca2d682f94f46b1973bdf5e77d85d77b8e53 ]

In terms of normal application usage, this list will always be empty.
And if an application does overflow a bit, it'll have a few entries.
However, nothing obviously prevents syzbot from running a test case
that generates a ton of overflow entries, and then flushing them can
take quite a while.

Check for needing to reschedule while flushing, and drop our locks and
do so if necessary. There's no state to maintain here as overflows
always prune from head-of-list, hence it's fine to drop and reacquire
the locks at the end of the loop.

Link: https://lore.kernel.org/io-uring/66ed061d.050a0220.29194.0053.GAE@google.com/


Reported-by: default avatar <syzbot+5fca234bd7eb378ff78e@syzkaller.appspotmail.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
Signed-off-by: default avatarBaokun Li <libaokun1@huawei.com>
parent d383ae29

io_uring/io_uring.c

+15 −0
Original line number Diff line number Diff line
@@ -705,6 +705,21 @@ static void __io_cqring_overflow_flush(struct io_ring_ctx *ctx) 
		memcpy(cqe, &ocqe->cqe, cqe_size);

		list_del(&ocqe->list);

		kfree(ocqe);



		/*

		 * For silly syzbot cases that deliberately overflow by huge

		 * amounts, check if we need to resched and drop and

		 * reacquire the locks if so. Nothing real would ever hit this.

		 * Ideally we'd have a non-posting unlock for this, but hard

		 * to care for a non-real case.

		 */

		if (need_resched()) {

			io_cq_unlock_post(ctx);

			mutex_unlock(&ctx->uring_lock);

			cond_resched();

			mutex_lock(&ctx->uring_lock);

			io_cq_lock(ctx);

		}

	}



	if (list_empty(&ctx->cq_overflow_list)) {