[PATCH 4.4 24/86] blktrace: fix unlocked access to init/start-stop/teardown

[Greg Kroah-Hartman]

From: Jens Axboe <ax...@kernel.dk>

commit 1f2cac107c591c24b60b115d6050adc213d10fc0 upstream.

sg.c calls into the blktrace functions without holding the proper queue
mutex for doing setup, start/stop, or teardown.

Add internal unlocked variants, and export the ones that do the proper
locking.

Fixes: 6da127ad0918 ("blktrace: Add blktrace ioctls to SCSI generic devices")
Tested-by: Dmitry Vyukov <dvyu...@google.com>
Signed-off-by: Jens Axboe <ax...@kernel.dk>
Signed-off-by: Ben Hutchings <ben.hutchi...@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 kernel/trace/blktrace.c |   58 +++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 48 insertions(+), 10 deletions(-)

--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -323,7 +323,7 @@ static void blk_trace_cleanup(struct blk
        put_probe_ref();
 }
 
-int blk_trace_remove(struct request_queue *q)
+static int __blk_trace_remove(struct request_queue *q)
 {
        struct blk_trace *bt;
 
@@ -336,6 +336,17 @@ int blk_trace_remove(struct request_queu
 
        return 0;
 }
+
+int blk_trace_remove(struct request_queue *q)
+{
+       int ret;
+
+       mutex_lock(&q->blk_trace_mutex);
+       ret = __blk_trace_remove(q);
+       mutex_unlock(&q->blk_trace_mutex);
+
+       return ret;
+}
 EXPORT_SYMBOL_GPL(blk_trace_remove);
 
 static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
@@ -546,9 +557,8 @@ err:
        return ret;
 }
 
-int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
-                   struct block_device *bdev,
-                   char __user *arg)
+static int __blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
+                            struct block_device *bdev, char __user *arg)
 {
        struct blk_user_trace_setup buts;
        int ret;
@@ -567,6 +577,19 @@ int blk_trace_setup(struct request_queue
        }
        return 0;
 }
+
+int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
+                   struct block_device *bdev,
+                   char __user *arg)
+{
+       int ret;
+
+       mutex_lock(&q->blk_trace_mutex);
+       ret = __blk_trace_setup(q, name, dev, bdev, arg);
+       mutex_unlock(&q->blk_trace_mutex);
+
+       return ret;
+}
 EXPORT_SYMBOL_GPL(blk_trace_setup);
 
 #if defined(CONFIG_COMPAT) && defined(CONFIG_X86_64)
@@ -603,7 +626,7 @@ static int compat_blk_trace_setup(struct
 }
 #endif
 
-int blk_trace_startstop(struct request_queue *q, int start)
+static int __blk_trace_startstop(struct request_queue *q, int start)
 {
        int ret;
        struct blk_trace *bt = q->blk_trace;
@@ -642,6 +665,17 @@ int blk_trace_startstop(struct request_q
 
        return ret;
 }
+
+int blk_trace_startstop(struct request_queue *q, int start)
+{
+       int ret;
+
+       mutex_lock(&q->blk_trace_mutex);
+       ret = __blk_trace_startstop(q, start);
+       mutex_unlock(&q->blk_trace_mutex);
+
+       return ret;
+}
 EXPORT_SYMBOL_GPL(blk_trace_startstop);
 
 /*
@@ -672,7 +706,7 @@ int blk_trace_ioctl(struct block_device
        switch (cmd) {
        case BLKTRACESETUP:
                bdevname(bdev, b);
-               ret = blk_trace_setup(q, b, bdev->bd_dev, bdev, arg);
+               ret = __blk_trace_setup(q, b, bdev->bd_dev, bdev, arg);
                break;
 #if defined(CONFIG_COMPAT) && defined(CONFIG_X86_64)
        case BLKTRACESETUP32:
@@ -683,10 +717,10 @@ int blk_trace_ioctl(struct block_device
        case BLKTRACESTART:
                start = 1;
        case BLKTRACESTOP:
-               ret = blk_trace_startstop(q, start);
+               ret = __blk_trace_startstop(q, start);
                break;
        case BLKTRACETEARDOWN:
-               ret = blk_trace_remove(q);
+               ret = __blk_trace_remove(q);
                break;
        default:
                ret = -ENOTTY;
@@ -704,10 +738,14 @@ int blk_trace_ioctl(struct block_device
  **/
 void blk_trace_shutdown(struct request_queue *q)
 {
+       mutex_lock(&q->blk_trace_mutex);
+
        if (q->blk_trace) {
-               blk_trace_startstop(q, 0);
-               blk_trace_remove(q);
+               __blk_trace_startstop(q, 0);
+               __blk_trace_remove(q);
        }
+
+       mutex_unlock(&q->blk_trace_mutex);
 }
 
 /*