CVE-2024-49863: vhost/scsi: null-ptr-dereference in vhost_scsi_get_req()
First published: Mon Oct 21 2024(Updated: )
In the Linux kernel, the following vulnerability has been resolved: vhost/scsi: null-ptr-dereference in vhost_scsi_get_req() Since commit 3f8ca2e115e5 ("vhost/scsi: Extract common handling code from control queue handler") a null pointer dereference bug can be triggered when guest sends an SCSI AN request. In vhost_scsi_ctl_handle_vq(), `vc.target` is assigned with `&v_req.tmf.lun[1]` within a switch-case block and is then passed to vhost_scsi_get_req() which extracts `vc->req` and `tpg`. However, for a `VIRTIO_SCSI_T_AN_*` request, tpg is not required, so `vc.target` is set to NULL in this branch. Later, in vhost_scsi_get_req(), `vc->target` is dereferenced without being checked, leading to a null pointer dereference bug. This bug can be triggered from guest. When this bug occurs, the vhost_worker process is killed while holding `vq->mutex` and the corresponding tpg will remain occupied indefinitely. Below is the KASAN report: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 1 PID: 840 Comm: poc Not tainted 6.10.0+ #1 Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:vhost_scsi_get_req+0x165/0x3a0 Code: 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 2b 02 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b 65 30 4c 89 e2 48 c1 ea 03 <0f> b6 04 02 4c 89 e2 83 e2 07 38 d0 7f 08 84 c0 0f 85 be 01 00 00 RSP: 0018:ffff888017affb50 EFLAGS: 00010246 RAX: dffffc0000000000 RBX: ffff88801b000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888017affcb8 RBP: ffff888017affb80 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: ffff888017affc88 R14: ffff888017affd1c R15: ffff888017993000 FS: 000055556e076500(0000) GS:ffff88806b100000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000200027c0 CR3: 0000000010ed0004 CR4: 0000000000370ef0 Call Trace: <TASK> ? show_regs+0x86/0xa0 ? die_addr+0x4b/0xd0 ? exc_general_protection+0x163/0x260 ? asm_exc_general_protection+0x27/0x30 ? vhost_scsi_get_req+0x165/0x3a0 vhost_scsi_ctl_handle_vq+0x2a4/0xca0 ? __pfx_vhost_scsi_ctl_handle_vq+0x10/0x10 ? __switch_to+0x721/0xeb0 ? __schedule+0xda5/0x5710 ? __kasan_check_write+0x14/0x30 ? _raw_spin_lock+0x82/0xf0 vhost_scsi_ctl_handle_kick+0x52/0x90 vhost_run_work_list+0x134/0x1b0 vhost_task_fn+0x121/0x350 ... </TASK> ---[ end trace 0000000000000000 ]--- Let's add a check in vhost_scsi_get_req. [whitespace fixes]
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux Kernel | >=4.20<5.10.227 | |
| Linux Kernel | >=5.11<5.15.168 | |
| Linux Kernel | >=5.16<6.1.113 | |
| Linux Kernel | >=6.2<6.6.55 | |
| Linux Kernel | >=6.7<6.10.14 | |
| Linux Kernel | >=6.11<6.11.3 | |
| Linux Kernel | =6.12-rc1 | |
| Linux Kernel | =6.12-rc2 | |
| debian/linux | <=5.10.223-1<=5.10.226-1 | 6.1.123-1 6.1.128-1 6.12.12-1 6.12.15-1 |
| debian/linux-6.1 | 6.1.119-1~deb11u1 |
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Reference Links
- https://git.kernel.org/stable/c/00fb5b23e1c9cdbe496f5cd6b40367cb895f6c93
- https://git.kernel.org/stable/c/221af82f606d928ccef19a16d35633c63026f1be
- https://git.kernel.org/stable/c/25613e6d9841a1f9fb985be90df921fa99f800de
- https://git.kernel.org/stable/c/46128370a72c431df733af5ebb065c4d48c9ad39
- https://git.kernel.org/stable/c/61517f33e76d2c5247c1e61e668693afe5b67e6f
- https://git.kernel.org/stable/c/6592347f06e2b19a624270a85ad4b3ae48c3b241
- https://git.kernel.org/stable/c/ace9c778a214da9c98d7b69d904d1b0816f4f681
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-49863
- https://nvd.nist.gov/vuln/detail/CVE-2024-49863
- https://launchpad.net/bugs/cve/CVE-2024-49863
- https://security-tracker.debian.org/tracker/CVE-2024-49863
- https://ubuntu.com/security/CVE-2024-49863
- https://git.kernel.org/linus/221af82f606d928ccef19a16d35633c63026f1be
Frequently Asked Questions
What is the severity of CVE-2024-49863?
CVE-2024-49863 is classified as a high severity vulnerability due to its potential to cause a null pointer dereference in the Linux kernel.
How do I fix CVE-2024-49863?
To mitigate CVE-2024-49863, you should upgrade to a patched version of the Linux kernel, specifically versions 6.12.11 or 6.12.12.
What versions of the Linux kernel are affected by CVE-2024-49863?
CVE-2024-49863 affects multiple versions of the Linux kernel including those from 4.20 up to 6.12-rc2.
What are the potential impacts of CVE-2024-49863?
The potential impacts of CVE-2024-49863 include system crashes and denial of service due to the null pointer dereference.
Which Linux distributions are likely affected by CVE-2024-49863?
CVE-2024-49863 is likely to affect any Linux distribution that uses the vulnerable versions of the kernel, particularly Debian-based systems.
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