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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>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <49C30098.6080107@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Li Zefan 2009-03-20 10:34:00 +08:00 committed by Ingo Molnar
parent cd649b8bb8
commit b125130b22
1 changed files with 11 additions and 2 deletions
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13
kernel/trace/blktrace.c
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@ -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;