diff options
| author | Tejun Heo <tj@kernel.org> | 2017-02-08 15:19:07 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-02-26 11:07:51 +0100 |
| commit | de5634875b604674561bf2e97ef58f213c83bc30 (patch) | |
| tree | c7a54307e228856adcf1c24dc4384586b9ca7e7c /mm | |
| parent | 15696979d80f9a978496878eade032fba23bb06b (diff) | |
block: fix double-free in the failure path of cgwb_bdi_init()
commit 5f478e4ea5c5560b4e40eb136991a09f9389f331 upstream.
When !CONFIG_CGROUP_WRITEBACK, bdi has single bdi_writeback_congested
at bdi->wb_congested. cgwb_bdi_init() allocates it with kzalloc() and
doesn't do further initialization. This usually works fine as the
reference count gets bumped to 1 by wb_init() and the put from
wb_exit() releases it.
However, when wb_init() fails, it puts the wb base ref automatically
freeing the wb and the explicit kfree() in cgwb_bdi_init() error path
ends up trying to free the same pointer the second time causing a
double-free.
Fix it by explicitly initilizing the refcnt to 1 and putting the base
ref from cgwb_bdi_destroy().
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Fixes: a13f35e87140 ("writeback: don't embed root bdi_writeback_congested in bdi_writeback")
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/backing-dev.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 9ef80bf441b3..a988d4ef39da 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -757,15 +757,20 @@ static int cgwb_bdi_init(struct backing_dev_info *bdi) if (!bdi->wb_congested) return -ENOMEM; + atomic_set(&bdi->wb_congested->refcnt, 1); + err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL); if (err) { - kfree(bdi->wb_congested); + wb_congested_put(bdi->wb_congested); return err; } return 0; } -static void cgwb_bdi_destroy(struct backing_dev_info *bdi) { } +static void cgwb_bdi_destroy(struct backing_dev_info *bdi) +{ + wb_congested_put(bdi->wb_congested); +} #endif /* CONFIG_CGROUP_WRITEBACK */ |