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authorTejun Heo <tj@kernel.org>2017-02-08 15:19:07 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-02-26 11:07:51 +0100
commitde5634875b604674561bf2e97ef58f213c83bc30 (patch)
treec7a54307e228856adcf1c24dc4384586b9ca7e7c /mm
parent15696979d80f9a978496878eade032fba23bb06b (diff)
downloadlinux-linaro-stable-de5634875b604674561bf2e97ef58f213c83bc30.tar.gz
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.c9
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 */