CVE-2024-26635: llc: Drop support for ETH_P_TR_802_2.
In the Linux kernel, the following vulnerability has been resolved:
llc: Drop support for ETHPTR8022.
syzbot reported an uninit-value bug below. [0]
llc supports ETHP8022 (0x0004) and used to support ETHPTR8022 (0x0011), and syzbot abused the latter to trigger the bug.
write$tun(r0, &(0x7f0000000040)={@val={0x0, 0x11}, @val, @mpls={[], @llc={@snap={0xaa, 0x1, ')', "90e5dd"}}}}, 0x16)
llcconnhandler() initialises local variables {saddr,daddr}.mac based on skb in llcpdudecodesa()/llcpdudecodeda() and passes them to llclookup().
However, the initialisation is done only when skb->protocol is htons(ETHP8022), otherwise, llclookupestablished() and llclookuplistener() will read garbage.
The missing initialisation existed prior to commit 211ed865108e ("net: delete all instances of special processing for token ring").
It removed the part to kick out the token ring stuff but forgot to close the door allowing ETHPTR8022 packets to sneak into llcrcv().
Let's remove llctrpackettype and complete the deprecation.
[0]: BUG: KMSAN: uninit-value in llclookupestablished+0xe9d/0xf90 llclookupestablished+0xe9d/0xf90 llclookup net/llc/llcconn.c:611 [inline] llcconnhandler+0x4bd/0x1360 net/llc/llcconn.c:791 llcrcv+0xfbb/0x14a0 net/llc/llcinput.c:206 netifreceiveskbonecore net/core/dev.c:5527 [inline] netifreceiveskb+0x1a6/0x5a0 net/core/dev.c:5641 netifreceiveskbinternal net/core/dev.c:5727 [inline] netifreceiveskb+0x58/0x660 net/core/dev.c:5786 tunrxbatched+0x3ee/0x980 drivers/net/tun.c:1555 tungetuser+0x53af/0x66d0 drivers/net/tun.c:2002 tunchrwriteiter+0x3af/0x5d0 drivers/net/tun.c:2048 callwriteiter include/linux/fs.h:2020 [inline] newsyncwrite fs/readwrite.c:491 [inline] vfswrite+0x8ef/0x1490 fs/readwrite.c:584 ksyswrite+0x20f/0x4c0 fs/readwrite.c:637 dosyswrite fs/readwrite.c:649 [inline] sesyswrite fs/readwrite.c:646 [inline] x64syswrite+0x93/0xd0 fs/readwrite.c:646 dosyscallx64 arch/x86/entry/common.c:51 [inline] dosyscall64+0x44/0x110 arch/x86/entry/common.c:82 entrySYSCALL64afterhwframe+0x63/0x6b
Local variable daddr created at: llcconnhandler+0x53/0x1360 net/llc/llcconn.c:783 llcrcv+0xfbb/0x14a0 net/llc/llcinput.c:206
CPU: 1 PID: 5004 Comm: syz-executor994 Not tainted 6.6.0-syzkaller-14500-g1c41041124bd #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2024-26635?
CVE-2024-26635 is considered a high-severity vulnerability that affects the Linux kernel.
How do I fix CVE-2024-26635?
To fix CVE-2024-26635, upgrade to the patched versions of the Linux kernel, specifically 5.10.223-1, 5.10.226-1, 6.1.119-1, 6.1.123-1, 6.12.10-1, or 6.12.11-1.
What systems are affected by CVE-2024-26635?
CVE-2024-26635 affects systems running specific versions of the Linux kernel, particularly Debian based distributions.
What specific feature of the Linux kernel is impacted by CVE-2024-26635?
CVE-2024-26635 relates to the LLC (Logical Link Control) layer, specifically dropping support for ETH_P_TR_802_2.
Is there a known exploit for CVE-2024-26635?
Yes, CVE-2024-26635 was initially reported by syzbot, indicating that it could be exploited, particularly under certain conditions.