Description

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 .
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_...

Classification

CVE ID: CVE-2024-26657

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.04% (probability of being exploited)

EPSS Percentile: 5.08% (scored less or equal to compared to others)

EPSS Date: 2025-02-04 (when was this score calculated)

References

https://git.kernel.org/stable/c/74cd204c7afe498aa9dcc3ebf0ecac53d477a429
https://git.kernel.org/stable/c/54b5b7275dfdec35812ccce70930cd7c4ee612b2
https://git.kernel.org/stable/c/f34e8bb7d6c6626933fe993e03ed59ae85e16abb

Timeline