CVE-2025-38476 — rpl: Fix use-after-free in rpl_do_srh_inline().

Affected: Linux

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

rpl: Fix use-after-free in rpl_do_srh_inline().

Running lwt_dst_cache_ref_loop.sh in selftest with KASAN triggers the splat below [0].

rpl_do_srh_inline() fetches ipv6_hdr(skb) and accesses it after skb_cow_head(), which is illegal as the header could be freed then.

Let's fix it by making oldhdr to a local struct instead of a pointer.

[0]: [root@fedora net]# ./lwt_dst_cache_ref_loop.sh ... TEST: rpl (input) [ 57.631529] ================================================================== BUG: KASAN: slab-use-after-free in rpl_do_srh_inline.isra.0 (net/ipv6/rpl_iptunnel.c:174) Read of size 40 at addr ffff888122bf96d8 by task ping6/1543

CPU: 50 UID: 0 PID: 1543 Comm: ping6 Not tainted 6.16.0-rc5-01302-gfadd1e6231b1 #23 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: <IRQ> dump_stack_lvl (lib/dump_stack.c:122) print_report (mm/kasan/report.c:409 mm/kasan/report.c:521) kasan_report (mm/kasan/report.c:221 mm/kasan/report.c:636) kasan_check_range (mm/kasan/generic.c:175 (discriminator 1) mm/kasan/generic.c:189 (discriminator 1)) __asan_memmove (mm/kasan/shadow.c:94 (discriminator 2)) rpl_do_srh_inline.isra.0 (net/ipv6/rpl_iptunnel.c:174) rpl_input (net/ipv6/rpl_iptunnel.c:201 net/ipv6/rpl_iptunnel.c:282) lwtunnel_input (net/core/lwtunnel.c:459) ipv6_rcv (./include/net/dst.h:471 (discriminator 1) ./include/net/dst.h:469 (di…

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CVE-2025-38476 — rpl: Fix use-after-free in rpl_do_srh_inline().