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

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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    98ac9cc4b445 Merge tag 'f2fs-fix-6.18-rc2' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16be6734580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bbd3e7f3c2e28265
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
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=111e7dcd980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1223a492580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f8ad8459a8da/disk-98ac9cc4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/28720fa307c1/vmlinux-98ac9cc4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e4f310acec99/bzImage-98ac9cc4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+878ddc3962f792e9af59@syzkaller.appspotmail.com

mac80211_hwsim hwsim5 wlan1: entered allmulticast mode
=====================================================
BUG: KMSAN: uninit-value in cfg80211_classify8021d+0x99d/0x12b0 net/wireless/util.c:1027
 cfg80211_classify8021d+0x99d/0x12b0 net/wireless/util.c:1027
 ieee80211_select_queue+0x37a/0x9e0 net/mac80211/wme.c:180
 __ieee80211_subif_start_xmit+0x60f/0x1d90 net/mac80211/tx.c:4304
 ieee80211_subif_start_xmit+0xa8/0x6d0 net/mac80211/tx.c:4538
 __netdev_start_xmit include/linux/netdevice.h:5248 [inline]
 netdev_start_xmit include/linux/netdevice.h:5257 [inline]
 xmit_one net/core/dev.c:3845 [inline]
 dev_hard_start_xmit+0x22f/0xa30 net/core/dev.c:3861
 __dev_queue_xmit+0x3c51/0x5e60 net/core/dev.c:4763
 dev_queue_xmit include/linux/netdevice.h:3365 [inline]
 packet_xmit+0x8f/0x710 net/packet/af_packet.c:275
 packet_snd net/packet/af_packet.c:3076 [inline]
 packet_sendmsg+0x9173/0xa2a0 net/packet/af_packet.c:3108
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x333/0x3d0 net/socket.c:742
 __sys_sendto+0x593/0x720 net/socket.c:2244
 __do_sys_sendto net/socket.c:2251 [inline]
 __se_sys_sendto net/socket.c:2247 [inline]
 __x64_sys_sendto+0x130/0x200 net/socket.c:2247
 x64_sys_call+0x3924/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:45
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4962 [inline]
 slab_alloc_node mm/slub.c:5265 [inline]
 kmem_cache_alloc_node_noprof+0x989/0x16b0 mm/slub.c:5317
 kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:579
 __alloc_skb+0x347/0x7d0 net/core/skbuff.c:670
 alloc_skb include/linux/skbuff.h:1383 [inline]
 alloc_skb_with_frags+0xc5/0xa60 net/core/skbuff.c:6671
 sock_alloc_send_pskb+0xacc/0xc60 net/core/sock.c:2965
 packet_alloc_skb net/packet/af_packet.c:2926 [inline]
 packet_snd net/packet/af_packet.c:3019 [inline]
 packet_sendmsg+0x743d/0xa2a0 net/packet/af_packet.c:3108
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x333/0x3d0 net/socket.c:742
 __sys_sendto+0x593/0x720 net/socket.c:2244
 __do_sys_sendto net/socket.c:2251 [inline]
 __se_sys_sendto net/socket.c:2247 [inline]
 __x64_sys_sendto+0x130/0x200 net/socket.c:2247
 x64_sys_call+0x3924/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:45
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 0 UID: 0 PID: 6051 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
=====================================================


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

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: Re: [syzbot] [wireless?] KMSAN: uninit-value in cfg80211_classify8021d
Author: listout@listout.xyz

On 20.10.2025 14:07, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    98ac9cc4b445 Merge tag 'f2fs-fix-6.18-rc2' of git://git.ke..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16be6734580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=bbd3e7f3c2e28265
> 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
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=111e7dcd980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1223a492580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/f8ad8459a8da/disk-98ac9cc4.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/28720fa307c1/vmlinux-98ac9cc4.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/e4f310acec99/bzImage-98ac9cc4.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+878ddc3962f792e9af59@syzkaller.appspotmail.com

#syz test

diff --git a/net/wireless/util.c b/net/wireless/util.c
index 56724b33af04..b7290912dffb 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -938,9 +938,9 @@ EXPORT_SYMBOL(ieee80211_amsdu_to_8023s);
 unsigned int cfg80211_classify8021d(struct sk_buff *skb,
 				    struct cfg80211_qos_map *qos_map)
 {
-	unsigned int dscp;
-	unsigned char vlan_priority;
-	unsigned int ret;
+	unsigned int dscp = 0;
+	unsigned char vlan_priority = 0;
+	unsigned int ret = 0;
 
 	/* skb->priority values from 256->263 are magic values to
 	 * directly indicate a specific 802.1d priority.  This is used

-- 
Regards,
listout

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

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: Re: [syzbot] [wireless?] KMSAN: uninit-value in cfg80211_classify8021d
Author: listout@listout.xyz

On 20.10.2025 14:07, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    98ac9cc4b445 Merge tag 'f2fs-fix-6.18-rc2' of git://git.ke..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16be6734580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=bbd3e7f3c2e28265
> 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
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=111e7dcd980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1223a492580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/f8ad8459a8da/disk-98ac9cc4.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/28720fa307c1/vmlinux-98ac9cc4.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/e4f310acec99/bzImage-98ac9cc4.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+878ddc3962f792e9af59@syzkaller.appspotmail.com
> 
> mac80211_hwsim hwsim5 wlan1: entered allmulticast mode
> =====================================================

#syz test

diff --git a/net/wireless/util.c b/net/wireless/util.c
index 56724b33af04..05bb49afd5ef 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -938,9 +938,9 @@ EXPORT_SYMBOL(ieee80211_amsdu_to_8023s);
 unsigned int cfg80211_classify8021d(struct sk_buff *skb,
 				    struct cfg80211_qos_map *qos_map)
 {
-	unsigned int dscp;
-	unsigned char vlan_priority;
-	unsigned int ret;
+	unsigned int dscp = 0;
+	unsigned char vlan_priority = 0;
+	unsigned int ret = 0;
 
 	/* skb->priority values from 256->263 are magic values to
 	 * directly indicate a specific 802.1d priority.  This is used
@@ -963,10 +963,18 @@ unsigned int cfg80211_classify8021d(struct sk_buff *skb,
 
 	switch (skb->protocol) {
 	case htons(ETH_P_IP):
-		dscp = ipv4_get_dsfield(ip_hdr(skb)) & 0xfc;
+		if (skb_network_header_len(skb) >= sizeof(struct iphdr)) {
+			struct iphdr *iph = ip_hdr(skb);
+			if (iph)
+				dscp = ipv4_get_dsfield(iph) & 0xfc;
+		}
 		break;
 	case htons(ETH_P_IPV6):
-		dscp = ipv6_get_dsfield(ipv6_hdr(skb)) & 0xfc;
+		if (skb_network_header_len(skb) >= sizeof(struct ipv6hdr)) {
+			struct ipv6hdr *ip6h = ipv6_hdr(skb);
+			if (ip6h)
+				dscp = ipv6_get_dsfield(ip6h) & 0xfc;
+		}
 		break;
 	case htons(ETH_P_MPLS_UC):
 	case htons(ETH_P_MPLS_MC): {

-- 
Regards,
listout

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

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linux-kernel@vger.kernel.org.

***

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

#syz test

Forwarded: test KMSAN: uninit-value in cfg80211_classify8021d

[syzbot]

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Subject: test KMSAN: uninit-value in cfg80211_classify8021d
Author: vnranganath.20@gmail.com

#syz test

Forwarded: Re: test KMSAN: uninit-value in cfg80211_classify8021d

[syzbot]

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linux-kernel@vger.kernel.org.

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Subject: Re: test 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 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 <vnranganath.20@gmail.com> wrote:
>
> #syz test

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

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

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

#syz test

On Wed, Nov 12, 2025 at 9:03 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=12614658580000
>

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

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

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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