From: Tadeusz Struk <tadeusz.struk@xxxxxxxxxx> commit 703535e6ae1e94c89a9c1396b4c7b6b41160ef0c upstream. No need to deduce command size in scsi_setup_scsi_cmnd() anymore as appropriate checks have been added to scsi_fill_sghdr_rq() function and the cmd_len should never be zero here. The code to do that wasn't correct anyway, as it used uninitialized cmd->cmnd, which caused a null-ptr-deref if the command size was zero as in the trace below. Fix this by removing the unneeded code. KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 0 PID: 1822 Comm: repro Not tainted 5.15.0 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014 Call Trace: blk_mq_dispatch_rq_list+0x7c7/0x12d0 __blk_mq_sched_dispatch_requests+0x244/0x380 blk_mq_sched_dispatch_requests+0xf0/0x160 __blk_mq_run_hw_queue+0xe8/0x160 __blk_mq_delay_run_hw_queue+0x252/0x5d0 blk_mq_run_hw_queue+0x1dd/0x3b0 blk_mq_sched_insert_request+0x1ff/0x3e0 blk_execute_rq_nowait+0x173/0x1e0 blk_execute_rq+0x15c/0x540 sg_io+0x97c/0x1370 scsi_ioctl+0xe16/0x28e0 sd_ioctl+0x134/0x170 blkdev_ioctl+0x362/0x6e0 block_ioctl+0xb0/0xf0 vfs_ioctl+0xa7/0xf0 do_syscall_64+0x3d/0xb0 entry_SYSCALL_64_after_hwframe+0x44/0xae ---[ end trace 8b086e334adef6d2 ]--- Kernel panic - not syncing: Fatal exception Link: https://lore.kernel.org/r/20211103170659.22151-2-tadeusz.struk@xxxxxxxxxx Fixes: 2ceda20f0a99 ("scsi: core: Move command size detection out of the fast path") Cc: Bart Van Assche <bvanassche@xxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: James E.J. Bottomley <jejb@xxxxxxxxxxxxx> Cc: Martin K. Petersen <martin.petersen@xxxxxxxxxx> Cc: <linux-scsi@xxxxxxxxxxxxxxx> Cc: <linux-kernel@xxxxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> # 5.15, 5.14, 5.10 Reported-by: syzbot+5516b30f5401d4dcbcae@xxxxxxxxxxxxxxxxxxxxxxxxx Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Tadeusz Struk <tadeusz.struk@xxxxxxxxxx> Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/scsi/scsi_lib.c | 2 -- 1 file changed, 2 deletions(-) --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1193,8 +1193,6 @@ static blk_status_t scsi_setup_scsi_cmnd } cmd->cmd_len = scsi_req(req)->cmd_len; - if (cmd->cmd_len == 0) - cmd->cmd_len = scsi_command_size(cmd->cmnd); cmd->cmnd = scsi_req(req)->cmd; cmd->transfersize = blk_rq_bytes(req); cmd->allowed = scsi_req(req)->retries;
