CVE-2024-56647

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

net: Fix icmp host relookup triggering iprtbug

arp link failure may trigger iprtbug while xfrm enabled, call trace is:

WARNING: CPU: 0 PID: 0 at net/ipv4/route.c:1241 iprtbug+0x14/0x20 Modules linked in: CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.12.0-rc6-00077-g2e1b3cc9d7f7 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 RIP: 0010:iprtbug+0x14/0x20 Call Trace: <IRQ> ipsendskb+0x14/0x40 __icmpsend+0x42d/0x6a0 ipv4linkfailure+0xe2/0x1d0 arperrorreport+0x3c/0x50 neighinvalidate+0x8d/0x100 neightimerhandler+0x2e1/0x330 calltimerfn+0x21/0x120 __runtimerbase.part.0+0x1c9/0x270 runtimersoftirq+0x4c/0x80 handlesoftirqs+0xac/0x280 irqexitrcu+0x62/0x80 sysvecapictimerinterrupt+0x77/0x90

The script below reproduces this scenario: ip xfrm policy add src 0.0.0.0/0 dst 0.0.0.0/0 \ dir out priority 0 ptype main flag localok icmp ip l a veth1 type veth ip a a 192.168.141.111/24 dev veth0 ip l s veth0 up ping 192.168.141.155 -c 1

icmproutelookup() create input routes for locally generated packets while xfrm relookup ICMP traffic.Then it will set input route (dst->out = iprtbug) to skb for DESTUNREACH.

For ICMP err triggered by locally generated packets, dst->dev of output route is loopback. Generally, xfrm relookup verification is not required on loopback interfaces (net.ipv4.conf.lo.disable_xfrm = 1).

Skip icmp relookup for locally generated packets to fix it.