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    Subject[PATCH 4.4 40/86] scsi: mptfusion: Fix null pointer dereferences in mptscsih_remove()
    Date
    From: Helge Deller <deller@gmx.de>

    commit 2f4843b172c2c0360ee7792ad98025fae7baefde upstream.

    The mptscsih_remove() function triggers a kernel oops if the Scsi_Host
    pointer (ioc->sh) is NULL, as can be seen in this syslog:

    ioc0: LSI53C1030 B2: Capabilities={Initiator,Target}
    Begin: Waiting for root file system ...
    scsi host2: error handler thread failed to spawn, error = -4
    mptspi: ioc0: WARNING - Unable to register controller with SCSI subsystem
    Backtrace:
    [<000000001045b7cc>] mptspi_probe+0x248/0x3d0 [mptspi]
    [<0000000040946470>] pci_device_probe+0x1ac/0x2d8
    [<0000000040add668>] really_probe+0x1bc/0x988
    [<0000000040ade704>] driver_probe_device+0x160/0x218
    [<0000000040adee24>] device_driver_attach+0x160/0x188
    [<0000000040adef90>] __driver_attach+0x144/0x320
    [<0000000040ad7c78>] bus_for_each_dev+0xd4/0x158
    [<0000000040adc138>] driver_attach+0x4c/0x80
    [<0000000040adb3ec>] bus_add_driver+0x3e0/0x498
    [<0000000040ae0130>] driver_register+0xf4/0x298
    [<00000000409450c4>] __pci_register_driver+0x78/0xa8
    [<000000000007d248>] mptspi_init+0x18c/0x1c4 [mptspi]

    This patch adds the necessary NULL-pointer checks. Successfully tested on
    a HP C8000 parisc workstation with buggy SCSI drives.

    Link: https://lore.kernel.org/r/20201022090005.GA9000@ls3530.fritz.box
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Helge Deller <deller@gmx.de>
    Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/message/fusion/mptscsih.c | 13 ++++++++-----
    1 file changed, 8 insertions(+), 5 deletions(-)

    --- a/drivers/message/fusion/mptscsih.c
    +++ b/drivers/message/fusion/mptscsih.c
    @@ -1176,8 +1176,10 @@ mptscsih_remove(struct pci_dev *pdev)

    scsi_remove_host(host);

    - if((hd = shost_priv(host)) == NULL)
    - return;
    + if (host == NULL)
    + hd = NULL;
    + else
    + hd = shost_priv(host);

    mptscsih_shutdown(pdev);

    @@ -1193,14 +1195,15 @@ mptscsih_remove(struct pci_dev *pdev)
    "Free'd ScsiLookup (%d) memory\n",
    ioc->name, sz1));

    - kfree(hd->info_kbuf);
    + if (hd)
    + kfree(hd->info_kbuf);

    /* NULL the Scsi_Host pointer
    */
    ioc->sh = NULL;

    - scsi_host_put(host);
    -
    + if (host)
    + scsi_host_put(host);
    mpt_detach(pdev);

    }

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