🇰🇷 한글 설명
Linux 커널의 mlx5 네트워크 드라이버에서 Flow Target Entry(FTE)를 삭제하는 과정 중 레이스 컨디션(Race Condition) 취약점이 발견되었습니다. 동일한 매치 값을 가진 규칙이 동시에 추가될 경우, 하드웨어 삭제 함수가 조기에 NULL로 설정되어 시스템 패닉이나 메모리 누수를 유발할 수 있습니다.
💡 쉬운 설명
네트워크 규칙을 지우는 도중에 똑같은 규칙을 새로 만들려고 하면 시스템이 충돌하여 멈출 수 있는 문제입니다. 이로 인해 서버가 갑자기 꺼지거나 메모리 오류가 발생할 수 있습니다.
🇺🇸 원문 (English)
In the Linux kernel, the following vulnerability has been resolved:
net/mlx5: fs, lock FTE when checking if active
The referenced commits introduced a two-step process for deleting FTEs:
- Lock the FTE, delete it from hardware, set the hardware deletion function
to NULL and unlock the FTE.
- Lock the parent flow group, delete the software copy of the FTE, and
remove it from the xarray.
However, this approach encounters a race condition if a rule with the same
match value is added simultaneously. In this scenario, fs_core may set the
hardware deletion function to NULL prematurely, causing a panic during
subsequent rule deletions.
To prevent this, ensure the active flag of the FTE is checked under a lock,
which will prevent the fs_core layer from attaching a new steering rule to
an FTE that is in the process of deletion.
[ 438.967589] MOSHE: 2496 mlx5_del_flow_rules del_hw_func
[ 438.968205] ------------[ cut here ]------------
[ 438.968654] refcount_t: decrement hit 0; leaking memory.
[ 438.969249] WARNING: CPU: 0 PID: 8957 at lib/refcount.c:31 refcount_warn_saturate+0xfb/0x110
[ 438.970054] Modules linked in: act_mirred cls_flower act_gact sch_ingress openvswitch nsh mlx5_vdpa vringh vhost_iotlb vdpa mlx5_ib mlx5_core xt_conntrack xt_MASQUERADE nf_conntrack_netlink nfnetlink xt_addrtype iptable_nat nf_nat br_netfilter rpcsec_gss_krb5 auth_rpcgss oid_registry overlay rpcrdma rdma_ucm ib_iser libiscsi scsi_transport_iscsi ib_umad rdma_cm ib_ipoib iw_cm ib_cm ib_uverbs ib_core zram zsmalloc fuse [last unloaded: cls_flower]
[ 438.973288] CPU: 0 UID: 0 PID: 8957 Comm: tc Not tainted 6.12.0-rc1+ #8
[ 438.973888] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
[ 438.974874] RIP: 0010:refcount_warn_saturate+0xfb/0x110
[ 438.975363] Code: 40 66 3b 82 c6 05 16 e9 4d 01 01 e8 1f 7c a0 ff 0f 0b c3 cc cc cc cc 48 c7 c7 10 66 3b 82 c6 05 fd e8 4d 01 01 e8 05 7c a0 ff <0f> 0b c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 90
[ 438.976947] RSP: 0018:ffff888124a53610 EFLAGS: 00010286
[ 438.977446] RAX: 0000000000000000 RBX: ffff888119d56de0 RCX: 0000000000000000
[ 438.978090] RDX: ffff88852c828700 RSI: ffff88852c81b3c0 RDI: ffff88852c81b3c0
[ 438.978721] RBP: ffff888120fa0e88 R08: 0000000000000000 R09: ffff888124a534b0
[ 438.979353] R10: 0000000000000001 R11: 0000000000000001 R12: ffff888119d56de0
[ 438.979979] R13: ffff888120fa0ec0 R14: ffff888120fa0ee8 R15: ffff888119d56de0
[ 438.980607] FS: 00007fe6dcc0f800(0000) GS:ffff88852c800000(0000) knlGS:0000000000000000
[ 438.983984] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 438.984544] CR2: 00000000004275e0 CR3: 0000000186982001 CR4: 0000000000372eb0
[ 438.985205] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 438.985842] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 438.986507] Call Trace:
[ 438.986799] <TASK>
[ 438.987070] ? __warn+0x7d/0x110
[ 438.987426] ? refcount_warn_saturate+0xfb/0x110
[ 438.987877] ? report_bug+0x17d/0x190
[ 438.988261] ? prb_read_valid+0x17/0x20
[ 438.988659] ? handle_bug+0x53/0x90
[ 438.989054] ? exc_invalid_op+0x14/0x70
[ 438.989458] ? asm_exc_invalid_op+0x16/0x20
[ 438.989883] ? refcount_warn_saturate+0xfb/0x110
[ 438.990348] mlx5_del_flow_rules+0x2f7/0x340 [mlx5_core]
[ 438.990932] __mlx5_eswitch_del_rule+0x49/0x170 [mlx5_core]
[ 438.991519] ? mlx5_lag_is_sriov+0x3c/0x50 [mlx5_core]
[ 438.992054] ? xas_load+0x9/0xb0
[ 438.992407] mlx5e_tc_rule_unoffload+0x45/0xe0 [mlx5_core]
[ 438.993037] mlx5e_tc_del_fdb_flow+0x2a6/0x2e0 [mlx5_core]
[ 438.993623] mlx5e_flow_put+0x29/0x60 [mlx5_core]
[ 438.994161] mlx5e_delete_flower+0x261/0x390 [mlx5_core]
[ 438.994728] tc_setup_cb_destroy+0xb9/0x190
[ 438.995150] fl_hw_destroy_filter+0x94/0xc0 [cls_flower]
[ 438.995650] fl_change+0x11a4/0x13c0 [cls_flower]
[ 438.996105] tc_new_tfilter+0x347/0xbc0
[ 438.996503] ? __
---truncated---
📍 영향받는 시스템
Linux kernel (mlx5 driver 사용 환경, 특히 6.12.0-rc1 및 관련 버전)
⚔️ 공격 벡터
동일한 매치 값을 가진 네트워크 트래픽 제어(tc) 규칙을 매우 빠른 속도로 생성 및 삭제하는 공격
🛡️ 대응 방법
FTE의 active 플래그를 락(Lock) 상태에서 확인하도록 수정된 최신 Linux 커널로 업데이트
🔧 검증 코드
출력된 커널 버전이 취약점이 해결된 패치 버전(6.12 이후 또는 배포판별 보안 패치 적용 버전)인지 확인합니다.