diff options
authorRoman Pen <roman.penyaev@profitbricks.com>2016-02-09 12:33:35 -0700
committerAlex Shi <alex.shi@linaro.org>2016-11-29 15:24:56 +0800
commit83595f56588d5f5d677e62a576b6248328862b34 (patch)
parent0a5b451a53d4d181f22ab309403646792e0ddad2 (diff)
block: fix module reference leak on put_disk() call for cgroups throttle
get_disk(),get_gendisk() calls have non explicit side effect: they increase the reference on the disk owner module. The following is the correct sequence how to get a disk reference and to put it: disk = get_gendisk(...); /* use disk */ owner = disk->fops->owner; put_disk(disk); module_put(owner); fs/block_dev.c is aware of this required module_put() call, but f.e. blkg_conf_finish(), which is located in block/blk-cgroup.c, does not put a module reference. To see a leakage in action cgroups throttle config can be used. In the following script I'm removing throttle for /dev/ram0 (actually this is NOP, because throttle was never set for this device): # lsmod | grep brd brd 5175 0 # i=100; while [ $i -gt 0 ]; do echo "1:0 0" > \ /sys/fs/cgroup/blkio/blkio.throttle.read_bps_device; i=$(($i - 1)); \ done # lsmod | grep brd brd 5175 100 Now brd module has 100 references. The issue is fixed by calling module_put() just right away put_disk(). Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com> Cc: Gi-Oh Kim <gi-oh.kim@profitbricks.com> Cc: Tejun Heo <tj@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: linux-block@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Jens Axboe <axboe@fb.com> (cherry picked from commit 39a169b62b415390398291080dafe63aec751e0a) Signed-off-by: Alex Shi <alex.shi@linaro.org>
1 files changed, 9 insertions, 0 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 9d359e05fad7..8161090a1970 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -788,6 +788,7 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
struct gendisk *disk;
struct blkcg_gq *blkg;
+ struct module *owner;
unsigned int major, minor;
int key_len, part, ret;
char *body;
@@ -804,7 +805,9 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
if (!disk)
return -ENODEV;
if (part) {
+ owner = disk->fops->owner;
+ module_put(owner);
return -ENODEV;
@@ -820,7 +823,9 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
ret = PTR_ERR(blkg);
+ owner = disk->fops->owner;
+ module_put(owner);
* If queue was bypassing, we should retry. Do so after a
* short msleep(). It isn't strictly necessary but queue
@@ -851,9 +856,13 @@ EXPORT_SYMBOL_GPL(blkg_conf_prep);
void blkg_conf_finish(struct blkg_conf_ctx *ctx)
__releases(ctx->disk->queue->queue_lock) __releases(rcu)
+ struct module *owner;
+ owner = ctx->disk->fops->owner;
+ module_put(owner);