CVE-2026-64132ipv6: ioam: refresh hdr pointer before ioam6_event()

Official description

In the Linux kernel, the following vulnerability has been resolved: ipv6: ioam: refresh hdr pointer before ioam6_event() Reported by Sashiko: In ipv6_hop_ioam(), the hdr pointer is initialized to point into the skb's linear data buffer. Later, the code calls skb_ensure_writable(), which might reallocate the buffer: if (skb_ensure_writable(skb, optoff + 2 + hdr->opt_len)) goto drop; /* Trace pointer may have changed */ trace = (struct ioam6_trace_hdr *)(skb_network_header(skb) + optoff + sizeof(*hdr)); ioam6_fill_trace_data(skb, ns, trace, true); ioam6_event(IOAM6_EVENT_TRACE, dev_net(skb->dev), GFP_ATOMIC, (void *)trace, hdr->opt_len - 2); If the skb is cloned or lacks sufficient linear headroom, skb_ensure_writable() will invoke pskb_expand_head(), which reallocates the skb's data buffer and frees the old one, invalidating pointers to it. While the code recalculates the trace pointer immediately after the call to skb_ensure_writable(), it fails to recalculate the hdr pointer. This patch fixes the above by recalculating the hdr pointer before passing hdr->opt_len to ioam6_event(), so that we avoid any UaF.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/769723124b7c3b2bfea4cf68ad292698b87c8d01
• https://git.kernel.org/stable/c/24de676da63c1122d2c13b0d546238b66d1b4e62
• https://git.kernel.org/stable/c/5af905aa8e91ff8d94572a1e089558f21dcf24ed
• https://git.kernel.org/stable/c/e46e6bc97fb1f339730ff1ba74267fbf48e7a422