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![Tejun Heo](https://secure.gravatar.com/avatar/3153fad76e09b4fe37ddc74d32312eb4.jpg?s=96&d=mm)
Tejun Heo committed 1cb3de83ab7
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>