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author | Roman Pen <roman.penyaev@profitbricks.com> | 2016-02-09 12:33:35 -0700 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-07-05 14:37:16 +0200 |
commit | 21d7c733251a5afd87374d3928738026c93e6261 (patch) | |
tree | 07cb70c12e19e2d58d525c362fd9fd9edaf3b88a /mm | |
parent | 2449a71eb98204fc54ff55ddd6825cc5141ce176 (diff) |
block: fix module reference leak on put_disk() call for cgroups throttle
commit 39a169b62b415390398291080dafe63aec751e0a upstream.
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>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
0 files changed, 0 insertions, 0 deletions