diff options
| author | Jens Axboe <axboe@kernel.dk> | 2024-09-20 02:51:20 -0600 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-10-17 15:24:18 +0200 |
| commit | f4ce3b5d26ce149e77e6b8e8f2058aa80e5b034e (patch) | |
| tree | e140b98ee4a50261a202f32377adbed80e980865 /io_uring/io_uring.c | |
| parent | 30884833361b308d91e39c6c8285251a556ad3cd (diff) | |
io_uring: check if we need to reschedule during overflow flush
[ 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: syzbot+5fca234bd7eb378ff78e@syzkaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'io_uring/io_uring.c')
| -rw-r--r-- | io_uring/io_uring.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 7b0a100e1139..39d8d1fc5c2b 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -701,6 +701,21 @@ 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)) { |