Call bdev_get_queue(bdev) after bdev->bd_disk has been initialized instead of just before that pointer has been initialized. This patch avoids that the following command

pktsetup 1 /dev/sr0

triggers the following kernel crash:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000548 IP: pkt_setup_dev+0x2db/0x670 [pktcdvd] CPU: 2 PID: 724 Comm: pktsetup Not tainted 4.15.0-rc4-dbg+ #1 Call Trace: pkt_ctl_ioctl+0xce/0x1c0 [pktcdvd] do_vfs_ioctl+0x8e/0x670 SyS_ioctl+0x3c/0x70 entry_SYSCALL_64_fastpath+0x23/0x9a

Reported-by: Maciej S. Szmigiero mail@maciej.szmigiero.name Fixes: commit ca18d6f769d2 ("block: Make most scsi_req_init() calls implicit") Signed-off-by: Bart Van Assche bart.vanassche@wdc.com Tested-by: Maciej S. Szmigiero mail@maciej.szmigiero.name Cc: Maciej S. Szmigiero mail@maciej.szmigiero.name Cc: stable@vger.kernel.org # v4.13 --- drivers/block/pktcdvd.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c index 2659b2534073..531a0915066b 100644 --- a/drivers/block/pktcdvd.c +++ b/drivers/block/pktcdvd.c @@ -2579,14 +2579,14 @@ static int pkt_new_dev(struct pktcdvd_device *pd, dev_t dev) bdev = bdget(dev); if (!bdev) return -ENOMEM; + ret = blkdev_get(bdev, FMODE_READ | FMODE_NDELAY, NULL); + if (ret) + return ret; if (!blk_queue_scsi_passthrough(bdev_get_queue(bdev))) { WARN_ONCE(true, "Attempt to register a non-SCSI queue\n"); - bdput(bdev); + blkdev_put(bdev, FMODE_READ | FMODE_NDELAY); return -EINVAL; } - ret = blkdev_get(bdev, FMODE_READ | FMODE_NDELAY, NULL); - if (ret) - return ret;

/* This is safe, since we have a reference from open(). */ __module_get(THIS_MODULE);