loop: Fix use-after-free issues
do_req_filebacked() calls blk_mq_complete_request() synchronously or asynchronously when using asynchronous I/O unless memory allocation fails. Hence, modify loop_handle_cmd() such that it does not dereference 'cmd' nor 'rq' after do_req_filebacked() finished unless we are sure that the request has not yet been completed. This patch fixes the following kernel crash: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000054 Call trace: css_put.42938+0x1c/0x1ac loop_process_work+0xc8c/0xfd4 loop_rootcg_workfn+0x24/0x34 process_one_work+0x244/0x558 worker_thread+0x400/0x8fc kthread+0x16c/0x1e0 ret_from_fork+0x10/0x20 Cc: Christoph Hellwig <hch@lst.de> Cc: Ming Lei <ming.lei@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Dan Schatzberg <schatzberg.dan@gmail.com> Fixes: c74d40e8 ("loop: charge i/o to mem and blk cg") Fixes: bc07c10a ("block: loop: support DIO & AIO") Signed-off-by:Bart Van Assche <bvanassche@acm.org> Reviewed-by:
Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20230314182155.80625-1-bvanassche@acm.orgSigned-off-by:
Jens Axboe <axboe@kernel.dk>
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