On (25/07/14 12:10), Sergey Senozhatsky wrote: > Date: Mon, 14 Jul 2025 12:10:16 +0900 > From: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx> > To: Phillip Potter <phil@xxxxxxxxxxxxxxxx> > Cc: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>, Jens Axboe > <axboe@xxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Chris Rankin > <rankincj@xxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, > linux-block@xxxxxxxxxxxxxxx > Subject: Re: cdrom: cdrom_mrw_exit() NULL ptr deref > Message-ID: <7kbmle3wlpeqcnfieelypkxzypfxoh7bqmuqn2d3hbjgbcm7mt@cze3mv7htbeg> > > On (25/07/11 21:46), Phillip Potter wrote: > > > <1>[335443.339244] BUG: kernel NULL pointer dereference, address: 0000000000000010 > > > <4>[335443.339301] RIP: 0010:blk_queue_enter+0x5a/0x250 [..] > > > <4>[335443.339439] blk_mq_alloc_request+0x16a/0x220 > > > <4>[335443.339450] scsi_execute_cmd+0x65/0x240 > > > <4>[335443.339458] sr_do_ioctl+0xe3/0x210 [sr_mod (HASH:ab3e 2)] > > > <4>[335443.339471] sr_packet+0x3d/0x50 [sr_mod (HASH:ab3e 2)] > > > <4>[335443.339482] cdrom_mrw_exit+0xc1/0x240 [cdrom (HASH:9d9a 3)] > > > <4>[335443.339497] sr_free_disk+0x45/0x60 [sr_mod (HASH:ab3e 2)] > > > <4>[335443.339506] disk_release+0xc8/0xe0 > > > <4>[335443.339515] device_release+0x39/0x90 > > > <4>[335443.339523] kobject_release+0x49/0xb0 > > > <4>[335443.339533] bdev_release+0x19/0x30 > > > <4>[335443.339540] deactivate_locked_super+0x3b/0x100 > > > <4>[335443.339548] cleanup_mnt+0xaa/0x160 > > > <4>[335443.339557] task_work_run+0x6c/0xb0 > > > <4>[335443.339563] exit_to_user_mode_prepare+0x102/0x120 > > > <4>[335443.339571] syscall_exit_to_user_mode+0x1a/0x30 > > > <4>[335443.339577] do_syscall_64+0x7e/0xa0 > > > <4>[335443.339582] ? exit_to_user_mode_prepare+0x44/0x120 > > > <4>[335443.339588] entry_SYSCALL_64_after_hwframe+0x55/0xbf > > > <4>[335443.339595] RIP: 0033:0x7d52bea41f07 > > > [..] > The device is detached already, I assume there isn't much that > cdrom_mrw_exit() can do at that point. If I read it correctly <4>[335443.339482] cdrom_mrw_exit+0xc1/0x240 [cdrom (HASH:9d9a 3)] <4>[335443.339497] sr_free_disk+0x45/0x60 [sr_mod (HASH:ab3e 2)] <4>[335443.339506] disk_release+0xc8/0xe0 <4>[335443.339515] device_release+0x39/0x90 device_release() calls dev->type->release() before dev->class->dev_release(). dev->type->release() probably should be scsi_device_dev_release() which, among other things, does sdev->request_queue = NULL, so dev->class->dev_release() is called too late to execute any scsi commands.
