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CVE-2024-49863

Description

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 codefrom control queue handler") a null pointer dereference bug can betriggered 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 tovhost_scsi_get_req() which extracts `vc->req` and `tpg`. However, fora `VIRTIO_SCSI_T_AN_*` request, tpg is not required, so `vc.target` isset to NULL in this branch. Later, in vhost_scsi_get_req(),`vc->target` is dereferenced without being checked, leading to a nullpointer 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 occupiedindefinitely.Below is the KASAN report:Oops: general protection fault, probably for non-canonical address0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN NOPTIKASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]CPU: 1 PID: 840 Comm: poc Not tainted 6.10.0+ #1Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS1.16.3-debian-1.16.3-2 04/01/2014RIP: 0010:vhost_scsi_get_req+0x165/0x3a0Code: 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 2b 02 00 0048 b8 00 00 00 00 00 fc ff df 4d 8b 65 30 4c 89 e2 48 c1 ea 03 <0f> b604 02 4c 89 e2 83 e2 07 38 d0 7f 08 84 c0 0f 85 be 01 00 00RSP: 0018:ffff888017affb50 EFLAGS: 00010246RAX: dffffc0000000000 RBX: ffff88801b000000 RCX: 0000000000000000RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888017affcb8RBP: ffff888017affb80 R08: 0000000000000000 R09: 0000000000000000R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000R13: ffff888017affc88 R14: ffff888017affd1c R15: ffff888017993000FS: 000055556e076500(0000) GS:ffff88806b100000(0000) knlGS:0000000000000000CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033CR2: 00000000200027c0 CR3: 0000000010ed0004 CR4: 0000000000370ef0Call Trace: ? 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... ---[ end trace 0000000000000000 ]---Let's add a check in vhost_scsi_get_req.[whitespace fixes]

POC

Reference

- 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

Github

- https://github.com/w4zu/Debian_security