🇰🇷 한글 설명
Linux 커널의 slip 드라이버 내 slhc_remember() 함수에서 악성 패킷에 대한 검증이 미흡하여 발생하는 취약점입니다. 패킷 크기만 확인하고 IPv4 및 TCP 헤더의 유효성을 충분히 검사하지 않아 초기화되지 않은 메모리 값을 참조할 수 있는 KMSAN 오류가 발생합니다.
💡 쉬운 설명
네트워크 패킷을 처리할 때 데이터가 올바른 형식인지 제대로 확인하지 않아 발생하는 보안 결함입니다. 공격자가 조작된 패킷을 보내 시스템의 메모리 오류를 유발하거나 비정상적인 동작을 일으킬 수 있습니다.
🇺🇸 원문 (English)
In the Linux kernel, the following vulnerability has been resolved:
slip: make slhc_remember() more robust against malicious packets
syzbot found that slhc_remember() was missing checks against
malicious packets [1].
slhc_remember() only checked the size of the packet was at least 20,
which is not good enough.
We need to make sure the packet includes the IPv4 and TCP header
that are supposed to be carried.
Add iph and th pointers to make the code more readable.
[1]
BUG: KMSAN: uninit-value in slhc_remember+0x2e8/0x7b0 drivers/net/slip/slhc.c:666
slhc_remember+0x2e8/0x7b0 drivers/net/slip/slhc.c:666
ppp_receive_nonmp_frame+0xe45/0x35e0 drivers/net/ppp/ppp_generic.c:2455
ppp_receive_frame drivers/net/ppp/ppp_generic.c:2372 [inline]
ppp_do_recv+0x65f/0x40d0 drivers/net/ppp/ppp_generic.c:2212
ppp_input+0x7dc/0xe60 drivers/net/ppp/ppp_generic.c:2327
pppoe_rcv_core+0x1d3/0x720 drivers/net/ppp/pppoe.c:379
sk_backlog_rcv+0x13b/0x420 include/net/sock.h:1113
__release_sock+0x1da/0x330 net/core/sock.c:3072
release_sock+0x6b/0x250 net/core/sock.c:3626
pppoe_sendmsg+0x2b8/0xb90 drivers/net/ppp/pppoe.c:903
sock_sendmsg_nosec net/socket.c:729 [inline]
__sock_sendmsg+0x30f/0x380 net/socket.c:744
____sys_sendmsg+0x903/0xb60 net/socket.c:2602
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2656
__sys_sendmmsg+0x3c1/0x960 net/socket.c:2742
__do_sys_sendmmsg net/socket.c:2771 [inline]
__se_sys_sendmmsg net/socket.c:2768 [inline]
__x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2768
x64_sys_call+0xb6e/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:308
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Uninit was created at:
slab_post_alloc_hook mm/slub.c:4091 [inline]
slab_alloc_node mm/slub.c:4134 [inline]
kmem_cache_alloc_node_noprof+0x6bf/0xb80 mm/slub.c:4186
kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:587
__alloc_skb+0x363/0x7b0 net/core/skbuff.c:678
alloc_skb include/linux/skbuff.h:1322 [inline]
sock_wmalloc+0xfe/0x1a0 net/core/sock.c:2732
pppoe_sendmsg+0x3a7/0xb90 drivers/net/ppp/pppoe.c:867
sock_sendmsg_nosec net/socket.c:729 [inline]
__sock_sendmsg+0x30f/0x380 net/socket.c:744
____sys_sendmsg+0x903/0xb60 net/socket.c:2602
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2656
__sys_sendmmsg+0x3c1/0x960 net/socket.c:2742
__do_sys_sendmmsg net/socket.c:2771 [inline]
__se_sys_sendmmsg net/socket.c:2768 [inline]
__x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2768
x64_sys_call+0xb6e/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:308
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
CPU: 0 UID: 0 PID: 5460 Comm: syz.2.33 Not tainted 6.12.0-rc2-syzkaller-00006-g87d6aab2389e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
📍 영향받는 시스템
Linux kernel (specifically versions using slip/slhc.c, including 6.12.0-rc2 and earlier)
⚔️ 공격 벡터
조작된 IPv4/TCP 헤더를 포함한 악성 네트워크 패킷을 전송하여 커널의 slhc_remember() 함수를 호출
🛡️ 대응 방법
Linux 커널을 최신 보안 패치가 적용된 버전으로 업데이트하여 slhc_remember()의 패킷 검증 로직을 강화해야 합니다.
🔧 검증 코드
출력된 커널 버전이 취약점이 해결된 패치 버전 이후인지 확인합니다.