CVE-2025-68813

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> ipvs: fix ipv4 null-ptr-deref in route error path<br /> <br /> The IPv4 code path in __ip_vs_get_out_rt() calls dst_link_failure()<br /> without ensuring skb-&gt;dev is set, leading to a NULL pointer dereference<br /> in fib_compute_spec_dst() when ipv4_link_failure() attempts to send<br /> ICMP destination unreachable messages.<br /> <br /> The issue emerged after commit ed0de45a1008 ("ipv4: recompile ip options<br /> in ipv4_link_failure") started calling __ip_options_compile() from<br /> ipv4_link_failure(). This code path eventually calls fib_compute_spec_dst()<br /> which dereferences skb-&gt;dev. An attempt was made to fix the NULL skb-&gt;dev<br /> dereference in commit 0113d9c9d1cc ("ipv4: fix null-deref in<br /> ipv4_link_failure"), but it only addressed the immediate dev_net(skb-&gt;dev)<br /> dereference by using a fallback device. The fix was incomplete because<br /> fib_compute_spec_dst() later in the call chain still accesses skb-&gt;dev<br /> directly, which remains NULL when IPVS calls dst_link_failure().<br /> <br /> The crash occurs when:<br /> 1. IPVS processes a packet in NAT mode with a misconfigured destination<br /> 2. Route lookup fails in __ip_vs_get_out_rt() before establishing a route<br /> 3. The error path calls dst_link_failure(skb) with skb-&gt;dev == NULL<br /> 4. ipv4_link_failure() → ipv4_send_dest_unreach() →<br /> __ip_options_compile() → fib_compute_spec_dst()<br /> 5. fib_compute_spec_dst() dereferences NULL skb-&gt;dev<br /> <br /> Apply the same fix used for IPv6 in commit 326bf17ea5d4 ("ipvs: fix<br /> ipv6 route unreach panic"): set skb-&gt;dev from skb_dst(skb)-&gt;dev before<br /> calling dst_link_failure().<br /> <br /> KASAN: null-ptr-deref in range [0x0000000000000328-0x000000000000032f]<br /> CPU: 1 PID: 12732 Comm: syz.1.3469 Not tainted 6.6.114 #2<br /> RIP: 0010:__in_dev_get_rcu include/linux/inetdevice.h:233<br /> RIP: 0010:fib_compute_spec_dst+0x17a/0x9f0 net/ipv4/fib_frontend.c:285<br /> Call Trace:<br /> <br /> spec_dst_fill net/ipv4/ip_options.c:232<br /> spec_dst_fill net/ipv4/ip_options.c:229<br /> __ip_options_compile+0x13a1/0x17d0 net/ipv4/ip_options.c:330<br /> ipv4_send_dest_unreach net/ipv4/route.c:1252<br /> ipv4_link_failure+0x702/0xb80 net/ipv4/route.c:1265<br /> dst_link_failure include/net/dst.h:437<br /> __ip_vs_get_out_rt+0x15fd/0x19e0 net/netfilter/ipvs/ip_vs_xmit.c:412<br /> ip_vs_nat_xmit+0x1d8/0xc80 net/netfilter/ipvs/ip_vs_xmit.c:764