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    Subject[PATCH 5.15 010/917] scsi: core: Remove command size deduction from scsi_setup_scsi_cmnd()
    Date
    From: Tadeusz Struk <tadeusz.struk@linaro.org>

    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@linaro.org
    Fixes: 2ceda20f0a99 ("scsi: core: Move command size detection out of the fast path")
    Cc: Bart Van Assche <bvanassche@acm.org>
    Cc: Christoph Hellwig <hch@lst.de>
    Cc: James E.J. Bottomley <jejb@linux.ibm.com>
    Cc: Martin K. Petersen <martin.petersen@oracle.com>
    Cc: <linux-scsi@vger.kernel.org>
    Cc: <linux-kernel@vger.kernel.org>
    Cc: <stable@vger.kernel.org> # 5.15, 5.14, 5.10
    Reported-by: syzbot+5516b30f5401d4dcbcae@syzkaller.appspotmail.com
    Reviewed-by: Bart Van Assche <bvanassche@acm.org>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org>
    Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/scsi/scsi_lib.c | 2 --
    1 file changed, 2 deletions(-)

    --- a/drivers/scsi/scsi_lib.c
    +++ b/drivers/scsi/scsi_lib.c
    @@ -1175,8 +1175,6 @@ 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;

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