# CVE-2021-47191: linux: In the Linux kernel, the following vulnerability has been resolved:  scsi: scsi_debug: Fix out-of-bound read in resp_...

CVE-2021-47191 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47191, released April 10, 2024. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-47191
- Priority: High
- CVSS: 7.1 (high)
- EPSS: 0.0024
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 10, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  scsi: scsi_debug: Fix out-of-bound read in resp_readcap16()  The following warning was observed running syzkaller:  [ 3813.830724] sg_write: data in/out 65466/242 bytes for SCSI command 0x9e-- guessing data in; [ 3813.830724]    program syz-executor not setting count and/or reply_len properly [ 3813.836956] ================================================================== [ 3813.839465] BUG: KASAN: stack-out-of-bounds in sg_copy_buffer+0x157/0x1e0 [ 3813.841773] Read of size 4096 at addr ffff8883cf80f540 by task syz-executor/1549 [ 3813.846612] Call Trace: [ 3813.846995]  dump_stack+0x108/0x15f [ 3813.847524]  print_address_description+0xa5/0x372 [ 3813.848243]  kasan_report.cold+0x236/0x2a8 [ 3813.849439]  check_memory_region+0x240/0x270 [ 3813.850094]  memcpy+0x30/0x80 [ 3813.850553]  sg_copy_buffer+0x157/0x1e0 [ 3813.853032]  sg_copy_from_buffer+0x13/0x20 [ 3813.853660]  fill_from_dev_buffer+0x135/0x370 [ 3813.854329]  resp_readcap16+0x1ac/0x280 [ 3813.856917]  schedule_resp+0x41f/0x1630 [ 3813.858203]  scsi_debug_queuecommand+0xb32/0x17e0 [ 3813.862699]  scsi_dispatch_cmd+0x330/0x950 [ 3813.863329]  scsi_request_fn+0xd8e/0x1710 [ 3813.863946]  __blk_run_queue+0x10b/0x230 [ 3813.864544]  blk_execute_rq_nowait+0x1d8/0x400 [ 3813.865220]  sg_common_write.isra.0+0xe61/0x2420 [ 3813.871637]  sg_write+0x6c8/0xef0 [ 3813.878853]  __vfs_write+0xe4/0x800 [ 3813.883487]  vfs_write+0x17b/0x530 [ 3813.884008]  ksys_write+0x103/0x270 [ 3813.886268]  __x64_sys_write+0x77/0xc0 [ 3813.886841]  do_syscall_64+0x106/0x360 [ 3813.887415]  entry_SYSCALL_64_after_hwframe+0x44/0xa9  This issue can be reproduced with the following syzkaller log:  r0 = openat(0xffffffffffffff9c, &(0x7f0000000040)='./file0\x00', 0x26e1, 0x0) r1 = syz_open_procfs(0xffffffffffffffff, &(0x7f0000000000)='fd/3\x00') open_by_handle_at(r1, &(0x7f00000003c0)=ANY=[@ANYRESHEX], 0x602000) r2 = syz_open_dev$sg(&(0x7f0000000000), 0x0, 0x40782) write$binfmt_aout(r2, &(0x7f0000000340)=ANY=[@ANYBLOB="00000000deff000000000000000000000000000000000000000000000000000047f007af9e107a41ec395f1bded7be24277a1501ff6196a83366f4e6362bc0ff2b247f68a972989b094b2da4fb3607fcf611a22dd04310d28c75039d"], 0x126)  In resp_readcap16() we get "int alloc_len" value -1104926854, and then pass the huge arr_len to fill_from_dev_buffer(), but arr is only 32 bytes. This leads to OOB in sg_copy_buffer().  To solve this issue, define alloc_len as u32.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.15.5-1 | [DEBIAN-CVE-2021-47191](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47191.md) | Apr 10, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.15.5-1 | [DEBIAN-CVE-2021-47191](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47191.md) | Apr 10, 2024 |
| Linux | linux Debian 14 | 5.15.5-1 | [DEBIAN-CVE-2021-47191](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47191.md) | Apr 10, 2024 |

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