🇰🇷 한글 설명
Linux 커널의 SMB 클라이언트에서 멀티채널 기능을 사용할 때 복호화 과정 중 Use-After-Free(UAF) 취약점이 발생합니다. 여러 개의 cifsd 스레드가 동일한 AEAD TFM 객체에 동시에 접근하여 동기식 복호화를 수행할 때 메모리 관리 오류가 발생할 수 있습니다.
💡 쉬운 설명
데이터를 암호화 해제하는 과정에서 여러 작업이 동시에 같은 메모리 공간을 사용하려다 발생하는 오류입니다. 이로 인해 시스템이 충돌하거나 보안 문제가 생길 수 있습니다.
🇺🇸 원문 (English)
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix UAF in decryption with multichannel
After commit f7025d861694 ("smb: client: allocate crypto only for
primary server") and commit b0abcd65ec54 ("smb: client: fix UAF in
async decryption"), the channels started reusing AEAD TFM from primary
channel to perform synchronous decryption, but that can't done as
there could be multiple cifsd threads (one per channel) simultaneously
accessing it to perform decryption.
This fixes the following KASAN splat when running fstest generic/249
with 'vers=3.1.1,multichannel,max_channels=4,seal' against Windows
Server 2022:
BUG: KASAN: slab-use-after-free in gf128mul_4k_lle+0xba/0x110
Read of size 8 at addr ffff8881046c18a0 by task cifsd/986
CPU: 3 UID: 0 PID: 986 Comm: cifsd Not tainted 6.15.0-rc1 #1
PREEMPT(voluntary)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-3.fc41
04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x5d/0x80
print_report+0x156/0x528
? gf128mul_4k_lle+0xba/0x110
? __virt_addr_valid+0x145/0x300
? __phys_addr+0x46/0x90
? gf128mul_4k_lle+0xba/0x110
kasan_report+0xdf/0x1a0
? gf128mul_4k_lle+0xba/0x110
gf128mul_4k_lle+0xba/0x110
ghash_update+0x189/0x210
shash_ahash_update+0x295/0x370
? __pfx_shash_ahash_update+0x10/0x10
? __pfx_shash_ahash_update+0x10/0x10
? __pfx_extract_iter_to_sg+0x10/0x10
? ___kmalloc_large_node+0x10e/0x180
? __asan_memset+0x23/0x50
crypto_ahash_update+0x3c/0xc0
gcm_hash_assoc_remain_continue+0x93/0xc0
crypt_message+0xe09/0xec0 [cifs]
? __pfx_crypt_message+0x10/0x10 [cifs]
? _raw_spin_unlock+0x23/0x40
? __pfx_cifs_readv_from_socket+0x10/0x10 [cifs]
decrypt_raw_data+0x229/0x380 [cifs]
? __pfx_decrypt_raw_data+0x10/0x10 [cifs]
? __pfx_cifs_read_iter_from_socket+0x10/0x10 [cifs]
smb3_receive_transform+0x837/0xc80 [cifs]
? __pfx_smb3_receive_transform+0x10/0x10 [cifs]
? __pfx___might_resched+0x10/0x10
? __pfx_smb3_is_transform_hdr+0x10/0x10 [cifs]
cifs_demultiplex_thread+0x692/0x1570 [cifs]
? __pfx_cifs_demultiplex_thread+0x10/0x10 [cifs]
? rcu_is_watching+0x20/0x50
? rcu_lockdep_current_cpu_online+0x62/0xb0
? find_held_lock+0x32/0x90
? kvm_sched_clock_read+0x11/0x20
? local_clock_noinstr+0xd/0xd0
? trace_irq_enable.constprop.0+0xa8/0xe0
? __pfx_cifs_demultiplex_thread+0x10/0x10 [cifs]
kthread+0x1fe/0x380
? kthread+0x10f/0x380
? __pfx_kthread+0x10/0x10
? local_clock_noinstr+0xd/0xd0
? ret_from_fork+0x1b/0x60
? local_clock+0x15/0x30
? lock_release+0x29b/0x390
? rcu_is_watching+0x20/0x50
? __pfx_kthread+0x10/0x10
ret_from_fork+0x31/0x60
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
</TASK>
📍 영향받는 시스템
Linux kernel (SMB client with multichannel enabled, specifically versions around 6.15.0-rc1 and affected by recent commits)
⚔️ 공격 벡터
SMB 멀티채널을 사용하는 네트워크 환경에서 특수하게 조작된 SMB 패킷을 전송하여 발생
🛡️ 대응 방법
Linux 커널을 최신 보안 패치가 적용된 버전으로 업데이트하십시오.
🔧 검증 코드
출력된 커널 버전이 취약점이 해결된 패치 버전 이후인지 확인하십시오.