Commit 40cb4cb7 authored by Will Rosenberg's avatar Will Rosenberg Committed by Paolo Abeni
Browse files

cipso: harden use of skb_cow() in cipso_v4_skbuff_setattr() 



If skb_cow() is passed a headroom <= -NET_SKB_PAD, it will trigger a
BUG. As a result, use cases should avoid calling with a headroom that
is negative to prevent triggering this issue.

This is the same code pattern fixed in Commit 58fc7342 ("ipv6:
BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()").

In cipso_v4_skbuff_setattr(), len_delta can become negative, leading to
a negative headroom passed to skb_cow(). However, the BUG is not
triggerable because the condition headroom <= -NET_SKB_PAD cannot be
satisfied due to limits on the IPv4 options header size.

Avoid potential problems in the future by only using skb_cow() to grow
the skb headroom.

Signed-off-by: default avatarWill Rosenberg <whrosenb@asu.edu>
Acked-by: default avatarPaul Moore <paul@paul-moore.com>
Link: https://patch.msgid.link/20260120155738.982771-1-whrosenb@asu.edu


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent b6d5a622

net/ipv4/cipso_ipv4.c

+2 −1
Original line number Diff line number Diff line
@@ -2196,7 +2196,8 @@ int cipso_v4_skbuff_setattr(struct sk_buff *skb, 
	/* if we don't ensure enough headroom we could panic on the skb_push()

	 * call below so make sure we have enough, we are also "mangling" the

	 * packet so we should probably do a copy-on-write call anyway */

	ret_val = skb_cow(skb, skb_headroom(skb) + len_delta);

	ret_val = skb_cow(skb,

			  skb_headroom(skb) + (len_delta > 0 ? len_delta : 0));

	if (ret_val < 0)

		return ret_val;