[PATCH 0/2] stable-5.12 backport fixes

[PATCH 0/2] stable-5.12 backport fixes

[Pavel Begunkov]

a298232ee6b9a1 ("io_uring: fix link timeout refs") was backported,
however the second chunk of it got discarded, which breaks io_uring.
It depends on another patch, so backport it first (patch 1/2) and
then apply a298232ee6b9a1 again (patch 2/2).

It's a bit messy, the patch will be in the tree twice. Let me
know if there is a better way.

Pavel Begunkov (2):
  io_uring: put link timeout req consistently
  io_uring: fix link timeout refs

 fs/io_uring.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

-- 
2.32.0

[PATCH 1/2] io_uring: put link timeout req consistently

[Pavel Begunkov]

[ Upstream commit df9727affa058f4f18e388b30247650f8ae13cd8 ]

Don't put linked timeout req in io_async_find_and_cancel() but do it in
io_link_timeout_fn(), so we have only one point for that and won't have
to do it differently as it's now (put vs put_deferred). Btw, improve a
bit io_async_find_and_cancel()'s locking.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d75b70957f245275ab7cba83e0ac9c1b86aae78a.1617287883.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io_uring.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 58ac04cca587..930c5d5a2b0b 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5727,12 +5727,9 @@ static void io_async_find_and_cancel(struct io_ring_ctx *ctx,
 	int ret;
 
 	ret = io_async_cancel_one(req->task->io_uring, sqe_addr, ctx);
-	if (ret != -ENOENT) {
-		spin_lock_irqsave(&ctx->completion_lock, flags);
-		goto done;
-	}
-
 	spin_lock_irqsave(&ctx->completion_lock, flags);
+	if (ret != -ENOENT)
+		goto done;
 	ret = io_timeout_cancel(ctx, sqe_addr);
 	if (ret != -ENOENT)
 		goto done;
@@ -5747,7 +5744,6 @@ static void io_async_find_and_cancel(struct io_ring_ctx *ctx,
 
 	if (ret < 0)
 		req_set_fail_links(req);
-	io_put_req(req);
 }
 
 static int io_async_cancel_prep(struct io_kiocb *req,
@@ -6310,8 +6306,8 @@ static enum hrtimer_restart io_link_timeout_fn(struct hrtimer *timer)
 		io_put_req_deferred(req, 1);
 	} else {
 		io_req_complete_post(req, -ETIME, 0);
-		io_put_req_deferred(req, 1);
 	}
+	io_put_req_deferred(req, 1);
 	return HRTIMER_NORESTART;
 }
 
-- 
2.32.0

[PATCH 2/2] io_uring: fix link timeout refs

[Pavel Begunkov]

[ Upstream commit a298232ee6b9a1d5d732aa497ff8be0d45b5bd82 ]

WARNING: CPU: 0 PID: 10242 at lib/refcount.c:28 refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28
RIP: 0010:refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28
Call Trace:
 __refcount_sub_and_test include/linux/refcount.h:283 [inline]
 __refcount_dec_and_test include/linux/refcount.h:315 [inline]
 refcount_dec_and_test include/linux/refcount.h:333 [inline]
 io_put_req fs/io_uring.c:2140 [inline]
 io_queue_linked_timeout fs/io_uring.c:6300 [inline]
 __io_queue_sqe+0xbef/0xec0 fs/io_uring.c:6354
 io_submit_sqe fs/io_uring.c:6534 [inline]
 io_submit_sqes+0x2bbd/0x7c50 fs/io_uring.c:6660
 __do_sys_io_uring_enter fs/io_uring.c:9240 [inline]
 __se_sys_io_uring_enter+0x256/0x1d60 fs/io_uring.c:9182

io_link_timeout_fn() should put only one reference of the linked timeout
request, however in case of racing with the master request's completion
first io_req_complete() puts one and then io_put_req_deferred() is
called.

Cc: stable@vger.kernel.org # 5.12+
Fixes: 9ae1f8dd372e0 ("io_uring: fix inconsistent lock state")
Reported-by: syzbot+a2910119328ce8e7996f@syzkaller.appspotmail.com
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/ff51018ff29de5ffa76f09273ef48cb24c720368.1620417627.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io_uring.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 930c5d5a2b0b..29a0af50a439 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6307,7 +6307,6 @@ static enum hrtimer_restart io_link_timeout_fn(struct hrtimer *timer)
 	} else {
 		io_req_complete_post(req, -ETIME, 0);
 	}
-	io_put_req_deferred(req, 1);
 	return HRTIMER_NORESTART;
 }
 
-- 
2.32.0

Re: [PATCH 0/2] stable-5.12 backport fixes

[Greg KH]

On Mon, Jul 19, 2021 at 12:54:21AM +0100, Pavel Begunkov wrote:
> a298232ee6b9a1 ("io_uring: fix link timeout refs") was backported,
> however the second chunk of it got discarded, which breaks io_uring.
> It depends on another patch, so backport it first (patch 1/2) and
> then apply a298232ee6b9a1 again (patch 2/2).
> 
> It's a bit messy, the patch will be in the tree twice. Let me
> know if there is a better way.
> 
> Pavel Begunkov (2):
>   io_uring: put link timeout req consistently
>   io_uring: fix link timeout refs
> 
>  fs/io_uring.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)

Not a problem, thanks for these.  This is going to be the last 5.12.y
release, so it shouldn't be that confusing.

thanks,

greg k-h

Re: [PATCH 0/2] stable-5.12 backport fixes

[Pavel Begunkov]

On 7/19/21 1:57 PM, Greg KH wrote:
> On Mon, Jul 19, 2021 at 12:54:21AM +0100, Pavel Begunkov wrote:
>> a298232ee6b9a1 ("io_uring: fix link timeout refs") was backported,
>> however the second chunk of it got discarded, which breaks io_uring.
>> It depends on another patch, so backport it first (patch 1/2) and
>> then apply a298232ee6b9a1 again (patch 2/2).
>>
>> It's a bit messy, the patch will be in the tree twice. Let me
>> know if there is a better way.
>>
>> Pavel Begunkov (2):
>>   io_uring: put link timeout req consistently
>>   io_uring: fix link timeout refs
>>
>>  fs/io_uring.c | 9 ++-------
>>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> Not a problem, thanks for these.  This is going to be the last 5.12.y
> release, so it shouldn't be that confusing.

Perfect, thanks Greg

-- 
Pavel Begunkov