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Michal Koutný
96e545410c
commit0ab5ee5a1bupstream. When multiple blkgs in the same blkcg are released concurrently, a use-after-free can occur. The race happens when one blkg's __blkcg_rstat_flush() removes another blkg's iostat entries via llist_del_all(). The second blkg sees an empty list and proceeds to free itself while the first is still iterating over its entries. Move the flush from __blkg_release() (RCU callback) to blkg_release() (before call_rcu). This ensures the RCU grace period waits for any concurrent flush's rcu_read_lock() section to complete before freeing. Cc: stable@vger.kernel.org Cc: Jay Shin <jaeshin@redhat.com> Cc: Tejun Heo <tj@kernel.org> Cc: Waiman Long <longman@redhat.com> Fixes:20cb1c2fb7("blk-cgroup: Flush stats before releasing blkcg_gq") Reported-by: coregee2000@gmail.com Closes: https://lore.kernel.org/linux-block/CAHPqNmwT9oRpem3J3erS_W0uSQND47LGGSBsNxP8E6uSUish1w@mail.gmail.com/ Signed-off-by: Ming Lei <ming.lei@redhat.com> Tested-by: Jose Fernandez (Anthropic) <jose.fernandez@linux.dev> Link: https://patch.msgid.link/20260205155425.342084-1-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>