linux-kernel - [PATCH 4.4 25/86] blktrace: fix trace mutex deadlock

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Message-Id: <20200518173455.557982692@linuxfoundation.org>
Date:   Mon, 18 May 2020 19:35:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Ben Hutchings <ben.hutchings@...ethink.co.uk>
Subject: [PATCH 4.4 25/86] blktrace: fix trace mutex deadlock

From: Jens Axboe <axboe@...nel.dk>

commit 2967acbb257a6a9bf912f4778b727e00972eac9b upstream.

A previous commit changed the locking around registration/cleanup,
but direct callers of blk_trace_remove() were missed. This means
that if we hit the error path in setup, we will deadlock on
attempting to re-acquire the queue trace mutex.

Fixes: 1f2cac107c59 ("blktrace: fix unlocked access to init/start-stop/teardown")
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Ben Hutchings <ben.hutchings@...ethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/trace/blktrace.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -572,7 +572,7 @@ static int __blk_trace_setup(struct requ
 		return ret;
 
 	if (copy_to_user(arg, &buts, sizeof(buts))) {
-		blk_trace_remove(q);
+		__blk_trace_remove(q);
 		return -EFAULT;
 	}
 	return 0;
@@ -618,7 +618,7 @@ static int compat_blk_trace_setup(struct
 		return ret;
 
 	if (copy_to_user(arg, &buts.name, ARRAY_SIZE(buts.name))) {
-		blk_trace_remove(q);
+		__blk_trace_remove(q);
 		return -EFAULT;
 	}