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cfq-iosched: fix sysfs oops when attempting to read unconfigured weights 

If none of the devices in the system are using CFQ, then attempting to
read:

/sys/fs/cgroup/blkio/blkio.leaf_weight

will results in a NULL dereference. Check for a valid cfq_group_data
struct before attempting to dereference it.

Reported-by: Andrey Wagin <avagin@gmail.com>
Fixes: e48453c3 ("block, cgroup: implement policy-specific per-blkcg data")
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jens Axboe 2015-06-19 10:19:36 -06:00
parent 4ceab71b9d
commit 9470e4a693
1 changed files with 12 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
block/cfq-iosched.c
View File

@ -1714,16 +1714,26 @@ static int cfqg_print_leaf_weight_device(struct seq_file *sf, void *v)
static int cfq_print_weight(struct seq_file *sf, void *v)
{
struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
struct cfq_group_data *cgd = blkcg_to_cfqgd(blkcg);
unsigned int val = 0;
seq_printf(sf, "%u\n", blkcg_to_cfqgd(blkcg)->weight);
if (cgd)
val = cgd->weight;
seq_printf(sf, "%u\n", val);
return 0;
}
static int cfq_print_leaf_weight(struct seq_file *sf, void *v)
{
struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
struct cfq_group_data *cgd = blkcg_to_cfqgd(blkcg);
unsigned int val = 0;
seq_printf(sf, "%u\n", blkcg_to_cfqgd(blkcg)->leaf_weight);
if (cgd)
val = cgd->leaf_weight;
seq_printf(sf, "%u\n", val);
return 0;
}