🇰🇷 한글 설명
Linux 커널의 drm/imagination 드라이버에서 GPU 대기 중 IRQ 핸들러가 실행될 경우 레지스터 접근 오류로 커널 크래시가 발생하는 동기화 문제입니다. synchronize_irq()를 suspend 콜백에 추가하여 IRQ 완료를 대기함으로써 해결됩니다.
💡 쉬운 설명
GPU를 절전 상태로 전환할 때 인터럽트 핸들러가 여전히 실행 중일 수 있어 시스템이 충돌합니다. 인터럽트가 완료될 때까지 기다린 후 절전을 수행해야 합니다.
🇺🇸 원문 (English)
In the Linux kernel, the following vulnerability has been resolved:
drm/imagination: Synchronize interrupts before suspending the GPU
The runtime PM suspend callback doesn't know whether the IRQ handler is
in progress on a different CPU core and doesn't wait for it to finish.
Depending on timing, the IRQ handler could be running while the GPU is
suspended, leading to kernel crashes when trying to access GPU
registers. See example signature below.
In a power off sequence initiated by the runtime PM suspend callback,
wait for any IRQ handlers in progress on other CPU cores to finish, by
calling synchronize_irq().
At the same time, remove the runtime PM resume/put calls in the threaded
IRQ handler. On top of not being the right approach to begin with, and
being at the wrong place as they should have wrapped all GPU register
accesses, the driver would hit a deadlock between synchronize_irq()
being called from a runtime PM suspend callback, holding the device
power lock, and the resume callback requiring the same.
Example crash signature on a TI AM68 SK platform:
[ 337.241218] SError Interrupt on CPU0, code 0x00000000bf000000 -- SError
[ 337.241239] CPU: 0 UID: 0 PID: 112 Comm: irq/234-gpu Tainted: G M 6.17.7-B2C-00005-g9c7bbe4ea16c #2 PREEMPT
[ 337.241246] Tainted: [M]=MACHINE_CHECK
[ 337.241249] Hardware name: Texas Instruments AM68 SK (DT)
[ 337.241252] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 337.241256] pc : pvr_riscv_irq_pending+0xc/0x24
[ 337.241277] lr : pvr_device_irq_thread_handler+0x64/0x310
[ 337.241282] sp : ffff800085b0bd30
[ 337.241284] x29: ffff800085b0bd50 x28: ffff0008070d9eab x27: ffff800083a5ce10
[ 337.241291] x26: ffff000806e48f80 x25: ffff0008070d9eac x24: 0000000000000000
[ 337.241296] x23: ffff0008068e9bf0 x22: ffff0008068e9bd0 x21: ffff800085b0bd30
[ 337.241301] x20: ffff0008070d9e00 x19: ffff0008068e9000 x18: 0000000000000001
[ 337.241305] x17: 637365645f656c70 x16: 0000000000000000 x15: ffff000b7df9ff40
[ 337.241310] x14: 0000a585fe3c0d0e x13: 000000999704f060 x12: 000000000002771a
[ 337.241314] x11: 00000000000000c0 x10: 0000000000000af0 x9 : ffff800085b0bd00
[ 337.241318] x8 : ffff0008071175d0 x7 : 000000000000b955 x6 : 0000000000000003
[ 337.241323] x5 : 0000000000000000 x4 : 0000000000000002 x3 : 0000000000000000
[ 337.241327] x2 : ffff800080e39d20 x1 : ffff800080e3fc48 x0 : 0000000000000000
[ 337.241333] Kernel panic - not syncing: Asynchronous SError Interrupt
[ 337.241337] CPU: 0 UID: 0 PID: 112 Comm: irq/234-gpu Tainted: G M 6.17.7-B2C-00005-g9c7bbe4ea16c #2 PREEMPT
[ 337.241342] Tainted: [M]=MACHINE_CHECK
[ 337.241343] Hardware name: Texas Instruments AM68 SK (DT)
[ 337.241345] Call trace:
[ 337.241348] show_stack+0x18/0x24 (C)
[ 337.241357] dump_stack_lvl+0x60/0x80
[ 337.241364] dump_stack+0x18/0x24
[ 337.241368] vpanic+0x124/0x2ec
[ 337.241373] abort+0x0/0x4
[ 337.241377] add_taint+0x0/0xbc
[ 337.241384] arm64_serror_panic+0x70/0x80
[ 337.241389] do_serror+0x3c/0x74
[ 337.241392] el1h_64_error_handler+0x30/0x48
[ 337.241400] el1h_64_error+0x6c/0x70
[ 337.241404] pvr_riscv_irq_pending+0xc/0x24 (P)
[ 337.241410] irq_thread_fn+0x2c/0xb0
[ 337.241416] irq_thread+0x170/0x334
[ 337.241421] kthread+0x12c/0x210
[ 337.241428] ret_from_fork+0x10/0x20
[ 337.241434] SMP: stopping secondary CPUs
[ 337.241451] Kernel Offset: disabled
[ 337.241453] CPU features: 0x040000,02002800,20002001,0400421b
[ 337.241456] Memory Limit: none
[ 337.457921] ---[ end Kernel panic - not syncing: Asynchronous SError Interrupt ]---
📍 영향받는 시스템
Linux 커널 6.17.x 이하의 drm/imagination 드라이버 (ARM64 기반 임베디드 시스템, TI AM68 SK 등)
⚔️ 공격 벡터
로컬 서비스 거부(DoS) - 특정 타이밍에 GPU 절전 시 IRQ 핸들러 실행으로 커널 패닉 유발
🛡️ 대응 방법
커널을 fix-commit 이상으로 업데이트하거나 synchronize_irq() 호출을 GPU suspend 콜백에 추가
🔧 검증 코드
커널 버전 6.18 이상이면 패치됨(echo 1), 6.17 이하면 미패치(echo 0). imagination 모듈 존재 확인으로 해당 드라이버 설치 여부 검증
uname -r | grep -qE '6\.(1[0-7]|[0-9])\.'; echo $?; modinfo imagination || echo 'Module not found'