test KMSAN: uninit-value in cfg80211_classify8021d

[Ranganath V N]

#syz test

[syzbot]

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=17c3b0b4580000

[Ranganath V N]

#syz test

diff --git a/net/wireless/util.c b/net/wireless/util.c
index 23bca5e687c1..c310876c6c72 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 ip6hdr 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 12:48 AM Ranganath V N <vnranga...@gmail.com> wrote:
>
> #syz test

[syzbot]

patch: https://syzkaller.appspot.com/x/patch.diff?x=17cfe532580000

[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):

[syzbot]

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=12614658580000

[syzbot]

patch: https://syzkaller.appspot.com/x/patch.diff?x=15358692580000

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+878ddc...@syzkaller.appspotmail.com
Tested-by: syzbot+878ddc...@syzkaller.appspotmail.com

Tested on:

commit: 24172e0d Merge tag 'arm64-fixes' of git://git.kernel.o..
git tree: upstream

console output: https://syzkaller.appspot.com/x/log.txt?x=12156b42580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1eab7413851950f4
dashboard link: https://syzkaller.appspot.com/bug?extid=878ddc3962f792e9af59
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch: https://syzkaller.appspot.com/x/patch.diff?x=11238212580000

Note: testing is done by a robot and is best-effort only.