block: fix double-free in the failure path of cgwb_bdi_init()
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: a13f35e871
("writeback: don't embed root bdi_writeback_congested in bdi_writeback")
Cc: stable@vger.kernel.org # v4.2+
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
parent
b35ba01ea6
commit
5f478e4ea5
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@ -759,15 +759,20 @@ static int cgwb_bdi_init(struct backing_dev_info *bdi)
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if (!bdi->wb_congested)
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return -ENOMEM;
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atomic_set(&bdi->wb_congested->refcnt, 1);
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err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
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if (err) {
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kfree(bdi->wb_congested);
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wb_congested_put(bdi->wb_congested);
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return err;
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}
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return 0;
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}
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static void cgwb_bdi_destroy(struct backing_dev_info *bdi) { }
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static void cgwb_bdi_destroy(struct backing_dev_info *bdi)
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{
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wb_congested_put(bdi->wb_congested);
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}
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#endif /* CONFIG_CGROUP_WRITEBACK */
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