From 882d4171a8950646413b1a3cbe0e4a6a612fe82e Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Tue, 2 Jan 2018 11:39:48 -0800 Subject: [PATCH] pktcdvd: Fix a recently introduced NULL pointer dereference 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 Fixes: commit ca18d6f769d2 ("block: Make most scsi_req_init() calls implicit") Signed-off-by: Bart Van Assche Tested-by: Maciej S. Szmigiero Cc: Maciej S. Szmigiero Cc: # v4.13 Signed-off-by: Jens Axboe --- drivers/block/pktcdvd.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 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; - if (!blk_queue_scsi_passthrough(bdev_get_queue(bdev))) { - WARN_ONCE(true, "Attempt to register a non-SCSI queue\n"); - bdput(bdev); - return -EINVAL; - } 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"); + blkdev_put(bdev, FMODE_READ | FMODE_NDELAY); + return -EINVAL; + } /* This is safe, since we have a reference from open(). */ __module_get(THIS_MODULE);