diff options
| author | Eric Dumazet <edumazet@google.com> | 2026-01-07 21:22:50 +0000 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-01-08 09:04:24 -0800 |
| commit | c92510f5e3f82ba11c95991824a41e59a9c5ed81 (patch) | |
| tree | 6329c392e3e007ded629b97ee38299def0fdf002 | |
| parent | 1f20c77496b3e253f18ea636f4f14069e383749d (diff) | |
arp: do not assume dev_hard_header() does not change skb->head
arp_create() is the only dev_hard_header() caller
making assumption about skb->head being unchanged.
A recent commit broke this assumption.
Initialize @arp pointer after dev_hard_header() call.
Fixes: db5b4e39c4e6 ("ip6_gre: make ip6gre_header() robust")
Reported-by: syzbot+58b44a770a1585795351@syzkaller.appspotmail.com
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260107212250.384552-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | net/ipv4/arp.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c index 7f3863daaa40..c8c3e1713c0e 100644 --- a/net/ipv4/arp.c +++ b/net/ipv4/arp.c @@ -564,7 +564,7 @@ struct sk_buff *arp_create(int type, int ptype, __be32 dest_ip, skb_reserve(skb, hlen); skb_reset_network_header(skb); - arp = skb_put(skb, arp_hdr_len(dev)); + skb_put(skb, arp_hdr_len(dev)); skb->dev = dev; skb->protocol = htons(ETH_P_ARP); if (!src_hw) @@ -572,12 +572,13 @@ struct sk_buff *arp_create(int type, int ptype, __be32 dest_ip, if (!dest_hw) dest_hw = dev->broadcast; - /* - * Fill the device header for the ARP frame + /* Fill the device header for the ARP frame. + * Note: skb->head can be changed. */ if (dev_hard_header(skb, dev, ptype, dest_hw, src_hw, skb->len) < 0) goto out; + arp = arp_hdr(skb); /* * Fill out the arp protocol part. * |