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authorMuchun Song <songmuchun@bytedance.com>2021-04-02 17:11:45 +0800
committerJan Kara <jack@suse.cz>2021-06-28 18:35:02 +0200
commit8b0ed8443ae6458786580d36b7d5f8125535c5d4 (patch)
tree4cb9fc32fd24cb332daeb2cbd6d0715d43a06828 /fs/udf
parentce1b06c5f5e7fd2af8bc89323d9eb3102d8e3fe2 (diff)
downloadlinux-8b0ed8443ae6458786580d36b7d5f8125535c5d4.tar.bz2
writeback: fix obtain a reference to a freeing memcg css
The caller of wb_get_create() should pin the memcg, because wb_get_create() relies on this guarantee. The rcu read lock only can guarantee that the memcg css returned by css_from_id() cannot be released, but the reference of the memcg can be zero. rcu_read_lock() memcg_css = css_from_id() wb_get_create(memcg_css) cgwb_create(memcg_css) // css_get can change the ref counter from 0 back to 1 css_get(memcg_css) rcu_read_unlock() Fix it by holding a reference to the css before calling wb_get_create(). This is not a problem I encountered in the real world. Just the result of a code review. Fixes: 682aa8e1a6a1 ("writeback: implement unlocked_inode_to_wb transaction and use it for stat updates") Link: https://lore.kernel.org/r/20210402091145.80635-1-songmuchun@bytedance.com Signed-off-by: Muchun Song <songmuchun@bytedance.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jan Kara <jack@suse.cz>
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