Bugzilla – Bug 1224642
VUL-0: REJECTED: CVE-2024-35941: kernel: net: skbuff: add overflow debug check to pull/push helpers
Last modified: 2024-06-07 08:34:23 UTC
In the Linux kernel, the following vulnerability has been resolved: net: skbuff: add overflow debug check to pull/push helpers syzbot managed to trigger following splat: BUG: KASAN: use-after-free in __skb_flow_dissect+0x4a3b/0x5e50 Read of size 1 at addr ffff888208a4000e by task a.out/2313 [..] __skb_flow_dissect+0x4a3b/0x5e50 __skb_get_hash+0xb4/0x400 ip_tunnel_xmit+0x77e/0x26f0 ipip_tunnel_xmit+0x298/0x410 .. Analysis shows that the skb has a valid ->head, but bogus ->data pointer. skb->data gets its bogus value via the neigh layer, which does: 1556 __skb_pull(skb, skb_network_offset(skb)); ... and the skb was already dodgy at this point: skb_network_offset(skb) returns a negative value due to an earlier overflow of skb->network_header (u16). __skb_pull thus "adjusts" skb->data by a huge offset, pointing outside skb->head area. Allow debug builds to splat when we try to pull/push more than INT_MAX bytes. After this, the syzkaller reproducer yields a more precise splat before the flow dissector attempts to read off skb->data memory: WARNING: CPU: 5 PID: 2313 at include/linux/skbuff.h:2653 neigh_connected_output+0x28e/0x400 ip_finish_output2+0xb25/0xed0 iptunnel_xmit+0x4ff/0x870 ipgre_xmit+0x78e/0xbb0 References: http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2024-35941 https://www.cve.org/CVERecord?id=CVE-2024-35941 https://git.kernel.org/stable/c/1b2b26595bb09febf14c5444c873ac4ec90a5a77 https://git.kernel.org/stable/c/219eee9c0d16f1b754a8b85275854ab17df0850a https://git.kernel.org/stable/c/8af60bb2b215f478b886f1d6d302fefa7f0b917d https://git.kernel.org/stable/c/fff05b2b004d9a8a2416d08647f3dc9068e357c8 https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2024/CVE-2024-35941.mbox
This is not a security fix. This is a debugging patch to trigger a warning (something that is considered a CVE worth kinda problem by the kernel CVE team) when unusual/unexpected data is processed. CONFIG_DEBUG_NET is not enabled in SLE15-SP6 and older kernels doesn't have this as this has been introduced by d268c1f5cfc9 ("net: add CONFIG_DEBUG_NET") in 5.19. Close as WONTFIX.
I have sent a revoke request.
REJECTED: https://lore.kernel.org/linux-cve-announce/2024060439-REJECTED-571b@gregkh/T/#u
closing, won't fix