CVE-2024-26657

In the Linux kernel, the following vulnerability has been resolved:

drm/sched: fix null-ptr-deref in init entity

The bug can be triggered by sending an amdgpu_cs_wait_ioctl to the AMDGPU DRM driver on any ASICs with valid context. The bug was reported by Joonkyo Jung joonkyoj@yonsei.ac.kr. For example the following code:

static void Syzkaller2(int fd)
{
union drm_amdgpu_ctx arg1;
union drm_amdgpu_wait_cs arg2;

arg1.in.op = AMDGPU_CTX_OP_ALLOC_CTX;
ret = drmIoctl(fd, 0x140106442 /* amdgpu_ctx_ioctl */, &arg1);

arg2.in.handle = 0x0;
arg2.in.timeout = 0x2000000000000;
arg2.in.ip_type = AMD_IP_VPE /* 0x9 */;
arg2->in.ip_instance = 0x0;
arg2.in.ring = 0x0;
arg2.in.ctx_id = arg1.out.alloc.ctx_id;

drmIoctl(fd, 0xc0206449 /* AMDGPU_WAIT_CS * /, &arg2);
}

The ioctl AMDGPU_WAIT_CS without previously submitted job could be assumed that the error should be returned, but the following commit 1decbf6bb0b4dc56c9da6c5e57b994ebfc2be3aa modified the logic and allowed to have sched_rq equal to NULL.

As a result when there is no job the ioctl AMDGPU_WAIT_CS returns success. The change fixes null-ptr-deref in init entity and the stack below demonstrates the error condition:

[ +0.000007] BUG: kernel NULL pointer dereference, address: 0000000000000028 [ +0.007086] #PF: supervisor read access in kernel mode [ +0.005234] #PF: error_code(0x0000) - not-present page [ +0.005232] PGD 0 P4D 0 [ +0.002501] Oops: 0000 [#1] PREEMPT SMP KASAN NOPTI [ +0.005034] CPU: 10 PID: 9229 Comm: amd_basic Tainted: G B W L 6.7.0+ #4 [ +0.007797] Hardware name: ASUS System Product Name/ROG STRIX B550-F GAMING (WI-FI), BIOS 1401 12/03/2020 [ +0.009798] RIP: 0010:drm_sched_entity_init+0x2d3/0x420 [gpu_sched] [ +0.006426] Code: 80 00 00 00 00 00 00 00 e8 1a 81 82 e0 49 89 9c 24 c0 00 00 00 4c 89 ef e8 4a 80 82 e0 49 8b 5d 00 48 8d 7b 28 e8 3d 80 82 e0 <48> 83 7b 28 00 0f 84 28 01 00 00 4d 8d ac 24 98 00 00 00 49 8d 5c [ +0.019094] RSP: 0018:ffffc90014c1fa40...