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net/sched: act_pedit: require matching IPv4 L4 protocol

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The extended IPv4 L4 header mode in act_pedit can select TCP or UDP
header fields without confirming that the IPv4 protocol field matches
the selected transport header.

That lets a rule written for TCP or UDP modify unrelated payload bytes
in a packet carrying a different protocol.

Verify that the IPv4 header is long enough, that the protocol matches
the selected TCP or UDP header, and that the packet is not a non-initial
fragment before applying TCP or UDP extended header edits.

Cc: stable+noautosel@kernel.org # in real rule sets the match confirms this before calling the action
Signed-off-by: Samuel Moelius <sam.moelius@trailofbits.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Samuel Moelius 2026-06-09 18:56:34 +00:00 committed by Jakub Kicinski
parent f6033078a9
commit d504a97857
1 changed files with 4 additions and 0 deletions
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4
net/sched/act_pedit.c
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@ -18,6 +18,7 @@
#include <linux/slab.h>
#include <linux/overflow.h>
#include <linux/unaligned.h>
#include <net/ip.h>
#include <net/ipv6.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
@ -331,6 +332,9 @@ static int pedit_l4_skb_offset(struct sk_buff *skb, int *hoffset, const int head
if (!iph)
goto out;
if (iph->ihl < 5 || iph->protocol != header_type ||
(iph->frag_off & htons(IP_OFFSET)))
goto out;
*hoffset = noff + iph->ihl * 4;
ret = 0;
break;