From bd99c71bd14072ce2920f6d0c2fe43df072c653c Mon Sep 17 00:00:00 2001
From: Hao Xu <haoxu@linux.alibaba.com>
Date: Wed, 22 Sep 2021 18:12:36 +0800
Subject: [PATCH] io_uring: fix race between poll completion and cancel_hash
insertion
Git-commit: bd99c71bd14072ce2920f6d0c2fe43df072c653c
Patch-mainline: v5.15-rc3
References: bsc#1199011
If poll arming and poll completion runs in parallel, there maybe races.
For instance, run io_poll_add in iowq and io_poll_task_func in original
context, then:
iowq original context
io_poll_add
vfs_poll
(interruption happens
tw queued to original
context) io_poll_task_func
generate cqe
del from cancel_hash[]
if !poll.done
insert to cancel_hash[]
The entry left in cancel_hash[], similar case for fast poll.
Fix it by set poll.done = true when del from cancel_hash[].
Fixes: 5082620fb2ca ("io_uring: terminate multishot poll for CQ ring overflow")
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20210922101238.7177-2-haoxu@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Takashi Iwai <tiwai@suse.de>
[ddiss: revert from stable-5.14.9 to mainline fix]
Acked-by: David Disseldorp <ddiss@suse.de>
---
fs/io_uring.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index e372d5b9f6dc..43530aae6180 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5337,10 +5337,8 @@ static bool __io_poll_complete(struct io_kiocb *req, __poll_t mask)
}
if (req->poll.events & EPOLLONESHOT)
flags = 0;
- if (!io_cqring_fill_event(ctx, req->user_data, error, flags)) {
- req->poll.done = true;
+ if (!io_cqring_fill_event(ctx, req->user_data, error, flags))
flags = 0;
- }
if (flags & IORING_CQE_F_MORE)
ctx->cq_extra++;
@@ -5371,6 +5369,7 @@ static void io_poll_task_func(struct io_kiocb *req, bool *locked)
if (done) {
io_poll_remove_double(req);
hash_del(&req->hash_node);
+ req->poll.done = true;
} else {
req->result = 0;
add_wait_queue(req->poll.head, &req->poll.wait);
@@ -5508,6 +5507,7 @@ static void io_async_task_func(struct io_kiocb *req, bool *locked)
hash_del(&req->hash_node);
io_poll_remove_double(req);
+ apoll->poll.done = true;
spin_unlock(&ctx->completion_lock);
if (!READ_ONCE(apoll->poll.canceled))
--
2.34.1