[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
=====================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

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

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KMSAN: uninit-value in cfg80211_classify8021d

mac80211_hwsim hwsim9 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:4969 [inline]
 slab_alloc_node mm/slub.c:5272 [inline]
 kmem_cache_alloc_node_noprof+0x989/0x16b0 mm/slub.c:5324
 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: 1 UID: 0 PID: 6608 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
=====================================================


Tested on:

commit:         6548d364 Merge tag 'cgroup-for-6.18-rc2-fixes' of git:..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15830d2f980000
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
patch:          https://syzkaller.appspot.com/x/patch.diff?x=14e3fde2580000

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

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KMSAN: uninit-value in cfg80211_classify8021d

RBP: 00007f2e3fe11f91 R08: 00002000000001c0 R09: 0000000000000014
R10: 0000000000000040 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2e3ffe6038 R14: 00007f2e3ffe5fa0 R15: 00007fff6dff3448
 </TASK>
---[ end trace 0000000000000000 ]---
=====================================================
BUG: KMSAN: uninit-value in cfg80211_classify8021d+0xc2f/0x1580 net/wireless/util.c:1035
 cfg80211_classify8021d+0xc2f/0x1580 net/wireless/util.c:1035
 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:4969 [inline]
 slab_alloc_node mm/slub.c:5272 [inline]
 kmem_cache_alloc_node_noprof+0x989/0x16b0 mm/slub.c:5324
 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: 1 UID: 0 PID: 6494 Comm: syz.0.17 Tainted: G        W           syzkaller #0 PREEMPT(none) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
=====================================================


Tested on:

commit:         552c5071 Merge tag 'vfio-v6.18-rc3' of https://github...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=101e8d2f980000
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
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1328d734580000

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

[syzbot]

Hello,

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

Reported-by: syzbot+878ddc3962f792e9af59@syzkaller.appspotmail.com
Tested-by: syzbot+878ddc3962f792e9af59@syzkaller.appspotmail.com

Tested on:

commit:         ba36dd5e Merge tag 'bpf-fixes' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1231abcd980000
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=16913f34580000

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

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

[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

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

[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=17cfe532580000

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@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=17cfe532580000
>

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

[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

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

[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=15358692580000

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

[syzbot]

Hello,

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

Reported-by: syzbot+878ddc3962f792e9af59@syzkaller.appspotmail.com
Tested-by: syzbot+878ddc3962f792e9af59@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.