From 6db8b56eed62baacaf37486e83378a72635c04cc Mon Sep 17 00:00:00 2001 From: Qanux Date: Wed, 11 Feb 2026 12:04:12 +0800 Subject: [PATCH] ipv6: ioam: fix heap buffer overflow in __ioam6_fill_trace_data() On the receive path, __ioam6_fill_trace_data() uses trace->nodelen to decide how much data to write for each node. It trusts this field as-is from the incoming packet, with no consistency check against trace->type (the 24-bit field that tells which data items are present). A crafted packet can set nodelen=0 while setting type bits 0-21, causing the function to write ~100 bytes past the allocated region (into skb_shared_info), which corrupts adjacent heap memory and leads to a kernel panic. Add a shared helper ioam6_trace_compute_nodelen() in ioam6.c to derive the expected nodelen from the type field, and use it: - in ioam6_iptunnel.c (send path, existing validation) to replace the open-coded computation; - in exthdrs.c (receive path, ipv6_hop_ioam) to drop packets whose nodelen is inconsistent with the type field, before any data is written. Per RFC 9197, bits 12-21 are each short (4-octet) fields, so they are included in IOAM6_MASK_SHORT_FIELDS (changed from 0xff100000 to 0xff1ffc00). Fixes: 9ee11f0fff20 ("ipv6: ioam: Data plane support for Pre-allocated Trace") Cc: stable@vger.kernel.org Signed-off-by: Junxi Qian Reviewed-by: Justin Iurman Link: https://patch.msgid.link/20260211040412.86195-1-qjx1298677004@gmail.com Signed-off-by: Jakub Kicinski --- include/net/ioam6.h | 2 ++ net/ipv6/exthdrs.c | 5 +++++ net/ipv6/ioam6.c | 14 ++++++++++++++ net/ipv6/ioam6_iptunnel.c | 10 +--------- 4 files changed, 22 insertions(+), 9 deletions(-) diff --git a/include/net/ioam6.h b/include/net/ioam6.h index 2cbbee6e806a..a75912fe247e 100644 --- a/include/net/ioam6.h +++ b/include/net/ioam6.h @@ -60,6 +60,8 @@ void ioam6_fill_trace_data(struct sk_buff *skb, struct ioam6_trace_hdr *trace, bool is_input); +u8 ioam6_trace_compute_nodelen(u32 trace_type); + int ioam6_init(void); void ioam6_exit(void); diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c index 209fdf1b1aa9..5e3610a926cf 100644 --- a/net/ipv6/exthdrs.c +++ b/net/ipv6/exthdrs.c @@ -931,6 +931,11 @@ static bool ipv6_hop_ioam(struct sk_buff *skb, int optoff) if (hdr->opt_len < 2 + sizeof(*trace) + trace->remlen * 4) goto drop; + /* Inconsistent Pre-allocated Trace header */ + if (trace->nodelen != + ioam6_trace_compute_nodelen(be32_to_cpu(trace->type_be32))) + goto drop; + /* Ignore if the IOAM namespace is unknown */ ns = ioam6_namespace(dev_net(skb->dev), trace->namespace_id); if (!ns) diff --git a/net/ipv6/ioam6.c b/net/ipv6/ioam6.c index 9553a3200081..08b7ac8c99b7 100644 --- a/net/ipv6/ioam6.c +++ b/net/ipv6/ioam6.c @@ -690,6 +690,20 @@ struct ioam6_namespace *ioam6_namespace(struct net *net, __be16 id) return rhashtable_lookup_fast(&nsdata->namespaces, &id, rht_ns_params); } +#define IOAM6_MASK_SHORT_FIELDS 0xff1ffc00 +#define IOAM6_MASK_WIDE_FIELDS 0x00e00000 + +u8 ioam6_trace_compute_nodelen(u32 trace_type) +{ + u8 nodelen = hweight32(trace_type & IOAM6_MASK_SHORT_FIELDS) + * (sizeof(__be32) / 4); + + nodelen += hweight32(trace_type & IOAM6_MASK_WIDE_FIELDS) + * (sizeof(__be64) / 4); + + return nodelen; +} + static void __ioam6_fill_trace_data(struct sk_buff *skb, struct ioam6_namespace *ns, struct ioam6_trace_hdr *trace, diff --git a/net/ipv6/ioam6_iptunnel.c b/net/ipv6/ioam6_iptunnel.c index 1fe7894f14dd..b9f6d892a566 100644 --- a/net/ipv6/ioam6_iptunnel.c +++ b/net/ipv6/ioam6_iptunnel.c @@ -22,9 +22,6 @@ #include #include -#define IOAM6_MASK_SHORT_FIELDS 0xff100000 -#define IOAM6_MASK_WIDE_FIELDS 0xe00000 - struct ioam6_lwt_encap { struct ipv6_hopopt_hdr eh; u8 pad[2]; /* 2-octet padding for 4n-alignment */ @@ -93,13 +90,8 @@ static bool ioam6_validate_trace_hdr(struct ioam6_trace_hdr *trace) trace->type.bit21 | trace->type.bit23) return false; - trace->nodelen = 0; fields = be32_to_cpu(trace->type_be32); - - trace->nodelen += hweight32(fields & IOAM6_MASK_SHORT_FIELDS) - * (sizeof(__be32) / 4); - trace->nodelen += hweight32(fields & IOAM6_MASK_WIDE_FIELDS) - * (sizeof(__be64) / 4); + trace->nodelen = ioam6_trace_compute_nodelen(fields); return true; } -- 2.47.3