From 447ec540233c60d6af4d68a164a5bc8ce7e975c1 Mon Sep 17 00:00:00 2001 From: Antoine Tenart Date: Thu, 9 Jul 2026 14:50:00 +0200 Subject: [PATCH] geneve: ensure the skb is writable before fixing its headers Make sure the IPv4/6 and UDP headers are writable before fixing them up in geneve_post_decap_hint. As skb_ensure_writable can reallocate the skb linear area, reload the GRO hint header pointer and only set the IPv4/6 header ones after the call. Fixes: fd0dd796576e ("geneve: use GRO hint option in the RX path") Reported-by: Sashiko Closes: https://sashiko.dev/#/patchset/20260529144713.780938-1-atenart%40kernel.org Signed-off-by: Antoine Tenart Reviewed-by: Simon Horman Link: https://patch.msgid.link/20260709125000.141092-1-atenart@kernel.org Signed-off-by: Jakub Kicinski --- drivers/net/geneve.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c index bed1c9713e0a..bb275b30d3e5 100644 --- a/drivers/net/geneve.c +++ b/drivers/net/geneve.c @@ -586,6 +586,7 @@ static int geneve_post_decap_hint(const struct sock *sk, struct sk_buff *skb, struct iphdr *iph; struct udphdr *uh; __be16 p; + int err; hint_off = geneve_sk_gro_hint_off(sk, *geneveh, &p, &len); if (!hint_off) @@ -610,12 +611,20 @@ static int geneve_post_decap_hint(const struct sock *sk, struct sk_buff *skb, !geneve_opt_gro_hint_validate(skb->data, gro_hint))) return -EINVAL; - ipv6h = (void *)skb->data + gro_hint->nested_nh_offset; - iph = (struct iphdr *)ipv6h; total_len = skb->len - gro_hint->nested_nh_offset; if (total_len >= GRO_LEGACY_MAX_SIZE) return -E2BIG; + err = skb_ensure_writable(skb, gro_hint->nested_tp_offset + sizeof(*uh)); + if (unlikely(err)) + return err; + + *geneveh = geneve_hdr(skb); + gro_hint = geneve_opt_gro_hint(*geneveh, hint_off); + + ipv6h = (void *)skb->data + gro_hint->nested_nh_offset; + iph = (struct iphdr *)ipv6h; + /* * After stripping the outer encap, the packet still carries a * tunnel encapsulation: the nested one.