Wind River Support Network

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.