Re: [PATCH] scsi: scsi_debug: fix type in min_t to avoid stack OOB

[Greg KH]

On Tue, Nov 02, 2021 at 07:47:58AM -0500, George Kennedy wrote:
> Change min_t() to use type "unsigned int" instead of type "int" to
> avoid stack out of bounds. With min_t() type "int" the values get
> sign extended and the larger value gets used causing stack out of bounds.
> 
> Reported-by: syzkaller <syzkaller@xxxxxxxxxxxxxxxx>
> Signed-off-by: George Kennedy <george.kennedy@xxxxxxxxxx>
> 
> BUG: KASAN: stack-out-of-bounds in memcpy include/linux/fortify-string.h:191 [inline]
> BUG: KASAN: stack-out-of-bounds in sg_copy_buffer+0x1de/0x240 lib/scatterlist.c:976
> Read of size 127 at addr ffff888072607128 by task syz-executor.7/18707
> 
> CPU: 1 PID: 18707 Comm: syz-executor.7 Not tainted 5.15.0-syzk #1
> Hardware name: Red Hat KVM, BIOS 1.13.0-2.module+el8.3.0+7860+a7792d29 04/01/2014
> Call Trace:
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0x89/0xb5 lib/dump_stack.c:106
>  print_address_description.constprop.9+0x28/0x160 mm/kasan/report.c:256
>  __kasan_report mm/kasan/report.c:442 [inline]
>  kasan_report.cold.14+0x7d/0x117 mm/kasan/report.c:459
>  check_region_inline mm/kasan/generic.c:183 [inline]
>  kasan_check_range+0x1a3/0x210 mm/kasan/generic.c:189
>  memcpy+0x23/0x60 mm/kasan/shadow.c:65
>  memcpy include/linux/fortify-string.h:191 [inline]
>  sg_copy_buffer+0x1de/0x240 lib/scatterlist.c:976
>  sg_copy_from_buffer+0x33/0x40 lib/scatterlist.c:1000
>  fill_from_dev_buffer.part.34+0x82/0x130 drivers/scsi/scsi_debug.c:1162
>  fill_from_dev_buffer drivers/scsi/scsi_debug.c:1888 [inline]
>  resp_readcap16+0x365/0x3b0 drivers/scsi/scsi_debug.c:1887
>  schedule_resp+0x4d8/0x1a70 drivers/scsi/scsi_debug.c:5478
>  scsi_debug_queuecommand+0x8c9/0x1ec0 drivers/scsi/scsi_debug.c:7533
>  scsi_dispatch_cmd drivers/scsi/scsi_lib.c:1520 [inline]
>  scsi_queue_rq+0x16b0/0x2d40 drivers/scsi/scsi_lib.c:1699
>  blk_mq_dispatch_rq_list+0xb9b/0x2700 block/blk-mq.c:1639
>  __blk_mq_sched_dispatch_requests+0x28f/0x590 block/blk-mq-sched.c:325
>  blk_mq_sched_dispatch_requests+0x105/0x190 block/blk-mq-sched.c:358
>  __blk_mq_run_hw_queue+0xe5/0x150 block/blk-mq.c:1761
>  __blk_mq_delay_run_hw_queue+0x4f8/0x5c0 block/blk-mq.c:1838
>  blk_mq_run_hw_queue+0x18d/0x350 block/blk-mq.c:1891
>  blk_mq_sched_insert_request+0x3db/0x4e0 block/blk-mq-sched.c:474
>  blk_execute_rq_nowait+0x16b/0x1c0 block/blk-exec.c:62
>  sg_common_write.isra.18+0xeb3/0x2000 drivers/scsi/sg.c:836
>  sg_new_write.isra.19+0x570/0x8c0 drivers/scsi/sg.c:774
>  sg_ioctl_common+0x14d6/0x2710 drivers/scsi/sg.c:939
>  sg_ioctl+0xa2/0x180 drivers/scsi/sg.c:1165
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:874 [inline]
>  __se_sys_ioctl fs/ioctl.c:860 [inline]
>  __x64_sys_ioctl+0x19d/0x220 fs/ioctl.c:860
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae

All of that needs to go above the signed-off-by lines, they need to be
last in the changelog text.

thanks,

greg k-h