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Subject[tip:tracing/blktrace] blktrace: avoid accessing NULL bdev->bd_disk
Commit-ID:  afaebb6720cc62df1b03e36c2f699b00cfee784e
Gitweb: http://git.kernel.org/tip/afaebb6720cc62df1b03e36c2f699b00cfee784e
Author: Li Zefan <lizf@cn.fujitsu.com>
AuthorDate: Fri, 20 Mar 2009 10:34:00 +0800
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 20 Mar 2009 11:20:07 +0100

blktrace: avoid accessing NULL bdev->bd_disk

bdev->bd_disk can be NULL, if the block device is not opened.

Try this against an unmounted partition, and you'll see NULL dereference:

# echo 1 > /sys/block/sda/sda5/enable
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <49C30098.6080107@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
kernel/trace/blktrace.c | 13 +++++++++++--
1 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index dfee6f9..108f4f7 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -1362,6 +1362,14 @@ static int blk_str2act_mask(const char *str)
return mask;
}

+static struct request_queue *blk_trace_get_queue(struct block_device *bdev)
+{
+ if (bdev->bd_disk == NULL)
+ return NULL;
+
+ return bdev_get_queue(bdev);
+}
+
static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
struct device_attribute *attr,
char *buf)
@@ -1376,9 +1384,10 @@ static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
if (bdev == NULL)
goto out_unlock_kernel;

- q = bdev_get_queue(bdev);
+ q = blk_trace_get_queue(bdev);
if (q == NULL)
goto out_bdput;
+
mutex_lock(&bdev->bd_mutex);

if (attr == &dev_attr_enable) {
@@ -1435,7 +1444,7 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
if (bdev == NULL)
goto out_unlock_kernel;

- q = bdev_get_queue(bdev);
+ q = blk_trace_get_queue(bdev);
if (q == NULL)
goto out_bdput;


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