Re: [syzbot] [wireless?] KMSAN: uninit-value in cfg80211_classify8021d

[Ranganath V N]

#syz test

diff --git a/net/wireless/util.c b/net/wireless/util.c
index 23bca5e687c1..150c5c632c54 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -963,13 +963,23 @@ unsigned int cfg80211_classify8021d(struct sk_buff *skb,

  switch (skb->protocol) {
  case htons(ETH_P_IP):
- if (!pskb_may_pull(skb, sizeof(struct iphdr)))
+ struct iphdr iph, *ip;
+
+ ip = skb_header_pointer(skb, sizeof(struct ethhdr),
+ sizeof(*ip), &iph);
+ if (!ip)
  return 0;
+
  dscp = ipv4_get_dsfield(ip_hdr(skb)) & 0xfc;
  break;
  case htons(ETH_P_IPV6):
- if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
+ struct ipv6hdr ip6h, *ip6;
+
+ ip6 = skb_header_pointer(skb, sizeof(struct ethhdr),
+ sizeof(*ip6), &ip6h);
+ if (!ip6)
  return 0;
+
  dscp = ipv6_get_dsfield(ipv6_hdr(skb)) & 0xfc;
  break;
  case htons(ETH_P_MPLS_UC):

On Wed, Nov 12, 2025 at 7:32 PM syzbot
<syzbot+878ddc3962f792e9af59@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot tried to test the proposed patch but the build/boot failed:
>
> failed to apply patch:
> checking file net/wireless/util.c
> Hunk #1 FAILED at 963.
> 1 out of 1 hunk FAILED
>
>
>
> Tested on:
>
> commit:         24172e0d Merge tag 'arm64-fixes' of git://git.kernel.o..
> git tree:       upstream
> kernel config:  https://syzkaller.appspot.com/x/.config?x=bbd3e7f3c2e28265
> dashboard link: https://syzkaller.appspot.com/bug?extid=878ddc3962f792e9af59
> compiler:
> patch:          https://syzkaller.appspot.com/x/patch.diff?x=17cfe532580000
>