blktrace: fix trace mutex deadlock

axboe · axboe · commit 2967acbb257a · 2017-11-27T12:03:58.000-07:00
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: 1f2cac1 ("blktrace: fix unlocked access to init/start-stop/teardown") Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
@@ -591,7 +591,7 @@ static int __blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 		return ret;
 
 	if (copy_to_user(arg, &buts, sizeof(buts))) {
-		blk_trace_remove(q);
+		__blk_trace_remove(q);
 		return -EFAULT;
 	}
 	return 0;
@@ -637,7 +637,7 @@ static int compat_blk_trace_setup(struct request_queue *q, char *name,
 		return ret;
 
 	if (copy_to_user(arg, &buts.name, ARRAY_SIZE(buts.name))) {
-		blk_trace_remove(q);
+		__blk_trace_remove(q);
 		return -EFAULT;
 	}
 

Original file line number	Diff line number	Diff line change
`@@ -591,7 +591,7 @@ static int __blk_trace_setup(struct request_queue q, char name, dev_t dev,`
`591`	`591`	`return ret;`
`592`	`592`
`593`	`593`	`if (copy_to_user(arg, &buts, sizeof(buts))) {`
`594`		`- blk_trace_remove(q);`
	`594`	`+ __blk_trace_remove(q);`
`595`	`595`	`return -EFAULT;`
`596`	`596`	`}`
`597`	`597`	`return 0;`
`@@ -637,7 +637,7 @@ static int compat_blk_trace_setup(struct request_queue q, char name,`
`637`	`637`	`return ret;`
`638`	`638`
`639`	`639`	`if (copy_to_user(arg, &buts.name, ARRAY_SIZE(buts.name))) {`
`640`		`- blk_trace_remove(q);`
	`640`	`+ __blk_trace_remove(q);`
`641`	`641`	`return -EFAULT;`
`642`	`642`	`}`
`643`	`643`