Re: [PATCH v2 resend 2/2] scsi:scsi_debug:Fix out-of-bound read in resp_report_tgtpgs

[Douglas Gilbert <dgilbert@interlog.com>]

On 2021-10-12 11:39 p.m., Ye Bin wrote:
> We got follow issue when run syzkaller:
> BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:377 [inline]
> BUG: KASAN: slab-out-of-bounds in sg_copy_buffer+0x150/0x1c0 lib/scatterlist.c:831
> Read of size 2132 at addr ffff8880aea95dc8 by task syz-executor.0/9815
> 
> CPU: 0 PID: 9815 Comm: syz-executor.0 Not tainted 4.19.202-00874-gfc0fe04215a9 #2
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0xe4/0x14a lib/dump_stack.c:118
>   print_address_description+0x73/0x280 mm/kasan/report.c:253
>   kasan_report_error mm/kasan/report.c:352 [inline]
>   kasan_report+0x272/0x370 mm/kasan/report.c:410
>   memcpy+0x1f/0x50 mm/kasan/kasan.c:302
>   memcpy include/linux/string.h:377 [inline]
>   sg_copy_buffer+0x150/0x1c0 lib/scatterlist.c:831
>   fill_from_dev_buffer+0x14f/0x340 drivers/scsi/scsi_debug.c:1021
>   resp_report_tgtpgs+0x5aa/0x770 drivers/scsi/scsi_debug.c:1772
>   schedule_resp+0x464/0x12f0 drivers/scsi/scsi_debug.c:4429
>   scsi_debug_queuecommand+0x467/0x1390 drivers/scsi/scsi_debug.c:5835
>   scsi_dispatch_cmd+0x3fc/0x9b0 drivers/scsi/scsi_lib.c:1896
>   scsi_request_fn+0x1042/0x1810 drivers/scsi/scsi_lib.c:2034
>   __blk_run_queue_uncond block/blk-core.c:464 [inline]
>   __blk_run_queue+0x1a4/0x380 block/blk-core.c:484
>   blk_execute_rq_nowait+0x1c2/0x2d0 block/blk-exec.c:78
>   sg_common_write.isra.19+0xd74/0x1dc0 drivers/scsi/sg.c:847
>   sg_write.part.23+0x6e0/0xd00 drivers/scsi/sg.c:716
>   sg_write+0x64/0xa0 drivers/scsi/sg.c:622
>   __vfs_write+0xed/0x690 fs/read_write.c:485
> kill_bdev:block_device:00000000e138492c
>   vfs_write+0x184/0x4c0 fs/read_write.c:549
>   ksys_write+0x107/0x240 fs/read_write.c:599
>   do_syscall_64+0xc2/0x560 arch/x86/entry/common.c:293
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
>   As with previous patch, we get 'alen' from command, and 'alen''s type is
>   int, If userspace pass large length we will get negative 'alen'.
>   So just set 'n'/'alen'/'rlen' with u32 type.
> 
> Signed-off-by: Ye Bin <yebin10@huawei.com>

Acked-by: Douglas Gilbert <dgilbert@interlog.com>

Thanks.

> ---
>   drivers/scsi/scsi_debug.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> index be0440545744..ead65cdfb522 100644
> --- a/drivers/scsi/scsi_debug.c
> +++ b/drivers/scsi/scsi_debug.c
> @@ -1896,8 +1896,9 @@ static int resp_report_tgtpgs(struct scsi_cmnd *scp,
>   	unsigned char *cmd = scp->cmnd;
>   	unsigned char *arr;
>   	int host_no = devip->sdbg_host->shost->host_no;
> -	int n, ret, alen, rlen;
>   	int port_group_a, port_group_b, port_a, port_b;
> +	u32 alen, n, rlen;
> +	int ret;
>   
>   	alen = get_unaligned_be32(cmd + 6);
>   	arr = kzalloc(SDEBUG_MAX_TGTPGS_ARR_SZ, GFP_ATOMIC);
> @@ -1959,9 +1960,9 @@ static int resp_report_tgtpgs(struct scsi_cmnd *scp,
>   	 * - The constructed command length
>   	 * - The maximum array size
>   	 */
> -	rlen = min_t(int, alen, n);
> +	rlen = min(alen, n);
>   	ret = fill_from_dev_buffer(scp, arr,
> -			   min_t(int, rlen, SDEBUG_MAX_TGTPGS_ARR_SZ));
> +			   min_t(u32, rlen, SDEBUG_MAX_TGTPGS_ARR_SZ));
>   	kfree(arr);
>   	return ret;
>   }
>