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

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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 58fc7342b5 ("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: Will Rosenberg <whrosenb@asu.edu>
Acked-by: Paul Moore <paul@paul-moore.com>
Link: https://patch.msgid.link/20260120155738.982771-1-whrosenb@asu.edu
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Will Rosenberg 2026-01-20 08:57:38 -07:00 committed by Paolo Abeni
parent b6d5a62231
commit 40cb4cb77e
1 changed files with 2 additions and 1 deletions
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3
net/ipv4/cipso_ipv4.c
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@ -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;