CVE-2024-50256

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_reject_ipv6: fix potential crash in nf_send_reset6()

I got a syzbot report without a repro [1] crashing in nf_send_reset6()

I think the issue is that dev->hard_header_len is zero, and we attempt

later to push an Ethernet header.

Use LL_MAX_HEADER, as other functions in net/ipv6/netfilter/nf_reject_ipv6.c.

[1]

skbuff: skb_under_panic: text:ffffffff89b1d008 len:74 put:14 head:ffff88803123aa00 data:ffff88803123a9f2 tail:0x3c end:0x140 dev:syz_tun

kernel BUG at net/core/skbuff.c:206 !

Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI

CPU: 0 UID: 0 PID: 7373 Comm: syz.1.568 Not tainted 6.12.0-rc2-syzkaller-00631-g6d858708d465 #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024

RIP: 0010:skb_panic net/core/skbuff.c:206 [inline]

RIP: 0010:skb_under_panic+0x14b/0x150 net/core/skbuff.c:216

Code: 0d 8d 48 c7 c6 60 a6 29 8e 48 8b 54 24 08 8b 0c 24 44 8b 44 24 04

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References