🇰🇷 한글 설명
Linux 커널의 AMDGPU 드라이버에서 메모리 예약 영역 크기가 잘못 설정되어 있는 취약점. 64K 페이지 크기 시스템에서 AMDGPU_VA_RESERVED_TRAP_SIZE(8KB)와 KFD_CWSR_TBA_TMA_SIZE(128KB)의 불일치로 인해 NULL 포인터 역참조 발생. rocminfo나 rccl 유닛 테스트 실행 시 커널 크래시.
💡 쉬운 설명
GPU 메모리 관리 영역의 크기가 시스템 페이지 크기에 맞게 조정되지 않아 메모리 접근 오류 발생. GPU 관련 프로그램 실행 시 시스템이 의도치 않게 중단될 수 있음.
🇺🇸 원문 (English)
In the Linux kernel, the following vulnerability has been resolved:
drm/amdgpu: Change AMDGPU_VA_RESERVED_TRAP_SIZE to 64KB
Currently, AMDGPU_VA_RESERVED_TRAP_SIZE is hardcoded to 8KB, while
KFD_CWSR_TBA_TMA_SIZE is defined as 2 * PAGE_SIZE. On systems with
4K pages, both values match (8KB), so allocation and reserved space
are consistent.
However, on 64K page-size systems, KFD_CWSR_TBA_TMA_SIZE becomes 128KB,
while the reserved trap area remains 8KB. This mismatch causes the
kernel to crash when running rocminfo or rccl unit tests.
Kernel attempted to read user page (2) - exploit attempt? (uid: 1001)
BUG: Kernel NULL pointer dereference on read at 0x00000002
Faulting instruction address: 0xc0000000002c8a64
Oops: Kernel access of bad area, sig: 11 [#1]
LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
CPU: 34 UID: 1001 PID: 9379 Comm: rocminfo Tainted: G E
6.19.0-rc4-amdgpu-00320-gf23176405700 #56 VOLUNTARY
Tainted: [E]=UNSIGNED_MODULE
Hardware name: IBM,9105-42A POWER10 (architected) 0x800200 0xf000006
of:IBM,FW1060.30 (ML1060_896) hv:phyp pSeries
NIP: c0000000002c8a64 LR: c00000000125dbc8 CTR: c00000000125e730
REGS: c0000001e0957580 TRAP: 0300 Tainted: G E
MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 24008268
XER: 00000036
CFAR: c00000000125dbc4 DAR: 0000000000000002 DSISR: 40000000
IRQMASK: 1
GPR00: c00000000125d908 c0000001e0957820 c0000000016e8100
c00000013d814540
GPR04: 0000000000000002 c00000013d814550 0000000000000045
0000000000000000
GPR08: c00000013444d000 c00000013d814538 c00000013d814538
0000000084002268
GPR12: c00000000125e730 c000007e2ffd5f00 ffffffffffffffff
0000000000020000
GPR16: 0000000000000000 0000000000000002 c00000015f653000
0000000000000000
GPR20: c000000138662400 c00000013d814540 0000000000000000
c00000013d814500
GPR24: 0000000000000000 0000000000000002 c0000001e0957888
c0000001e0957878
GPR28: c00000013d814548 0000000000000000 c00000013d814540
c0000001e0957888
NIP [c0000000002c8a64] __mutex_add_waiter+0x24/0xc0
LR [c00000000125dbc8] __mutex_lock.constprop.0+0x318/0xd00
Call Trace:
0xc0000001e0957890 (unreliable)
__mutex_lock.constprop.0+0x58/0xd00
amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu+0x6fc/0xb60 [amdgpu]
kfd_process_alloc_gpuvm+0x54/0x1f0 [amdgpu]
kfd_process_device_init_cwsr_dgpu+0xa4/0x1a0 [amdgpu]
kfd_process_device_init_vm+0xd8/0x2e0 [amdgpu]
kfd_ioctl_acquire_vm+0xd0/0x130 [amdgpu]
kfd_ioctl+0x514/0x670 [amdgpu]
sys_ioctl+0x134/0x180
system_call_exception+0x114/0x300
system_call_vectored_common+0x15c/0x2ec
This patch changes AMDGPU_VA_RESERVED_TRAP_SIZE to 64 KB and
KFD_CWSR_TBA_TMA_SIZE to the AMD GPU page size. This means we reserve
64 KB for the trap in the address space, but only allocate 8 KB within
it. With this approach, the allocation size never exceeds the reserved
area.
(cherry picked from commit 31b8de5e55666f26ea7ece5f412b83eab3f56dbb)
📍 영향받는 시스템
Linux kernel 6.19 이전 버전, 64K 페이지 크기 사용 시스템 (특히 IBM POWER10, ARM64 등 고용량 페이지 아키텍처)
⚔️ 공격 벡터
로컬 사용자 권한으로 rocminfo, rccl 테스트 등 GPU 초기화 코드 실행하여 커널 크래시 유발
🛡️ 대응 방법
Linux kernel을 패치된 버전(6.19.0-rc4 이상)으로 업그레이드하거나 AMDGPU_VA_RESERVED_TRAP_SIZE를 64KB로 수정
🔧 검증 코드
출력된 커널 버전이 6.19.0-rc4 이상이면 패치됨, 그 이전 버전이면 취약한 상태. 또는 /boot/config에서 AMDGPU 관련 설정 확인.
uname -r | grep -E '^[0-9]+\.[0-9]+' && echo 'Check if version >= 6.19.0-rc4'