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

[syzbot <syzbot+878ddc3962f792e9af59@syzkaller.appspotmail.com>]

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***

Subject: Re: [syzbot] [wireless?] KMSAN: uninit-value in cfg80211_classify8021d
Author: vnranganath.20@gmail.com

#syz test
diff --git a/net/wireless/util.c b/net/wireless/util.c
index 56724b33af04..f2a6644d854e 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -963,9 +963,23 @@ unsigned int cfg80211_classify8021d(struct sk_buff *skb,

        switch (skb->protocol) {
        case htons(ETH_P_IP):
+               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):
+               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 9:52 PM syzbot
<syzbot+878ddc3962f792e9af59@syzkaller.appspotmail.com> 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=15358692580000
>
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