Re: [syzbot] [bridge?] KMSAN: uninit-value in netif_skb_features (4)

Re: [syzbot] [bridge?] KMSAN: uninit-value in netif_skb_features (4)

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    ca4ee40bf13d Partly revert "drm/hyperv: Remove reference t..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1575c722580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4b4f2aab682301f1
dashboard link: https://syzkaller.appspot.com/bug?extid=1543a7d954d9c6d00407
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1044ec02580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10e3fe5a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/68f5e4558a91/disk-ca4ee40b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ea1eab60444d/vmlinux-ca4ee40b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cc7e3debdec4/bzImage-ca4ee40b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in gso_features_check net/core/dev.c:3804 [inline]
BUG: KMSAN: uninit-value in netif_skb_features+0x6fb/0x1870 net/core/dev.c:3828
 gso_features_check net/core/dev.c:3804 [inline]
 netif_skb_features+0x6fb/0x1870 net/core/dev.c:3828
 validate_xmit_skb+0xb6/0x2400 net/core/dev.c:4003
 validate_xmit_skb_list+0xd4/0x320 net/core/dev.c:4065
 sch_direct_xmit+0xd4/0xcf0 net/sched/sch_generic.c:332
 __dev_xmit_skb net/core/dev.c:4179 [inline]
 __dev_queue_xmit+0x3016/0x5a50 net/core/dev.c:4795
 dev_queue_xmit include/linux/netdevice.h:3384 [inline]
 packet_xmit+0x8f/0x710 net/packet/af_packet.c:275
 packet_snd net/packet/af_packet.c:3077 [inline]
 packet_sendmsg+0x91d9/0xa320 net/packet/af_packet.c:3109
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xfe7/0x1080 net/socket.c:2592
 ___sys_sendmsg+0x271/0x3b0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x211/0x3e0 net/socket.c:2681
 x64_sys_call+0x1e20/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x134/0xf80 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:4466 [inline]
 slab_alloc_node mm/slub.c:4788 [inline]
 kmem_cache_alloc_node_noprof+0x3cd/0x12d0 mm/slub.c:4840
 kmalloc_reserve net/core/skbuff.c:613 [inline]
 __alloc_skb+0x855/0x1190 net/core/skbuff.c:713
 alloc_skb include/linux/skbuff.h:1383 [inline]
 alloc_skb_with_frags+0xc5/0xa60 net/core/skbuff.c:6750
 sock_alloc_send_pskb+0xacb/0xc60 net/core/sock.c:2995
 packet_alloc_skb net/packet/af_packet.c:2927 [inline]
 packet_snd net/packet/af_packet.c:3020 [inline]
 packet_sendmsg+0x7477/0xa320 net/packet/af_packet.c:3109
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xfe7/0x1080 net/socket.c:2592
 ___sys_sendmsg+0x271/0x3b0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x211/0x3e0 net/socket.c:2681
 x64_sys_call+0x1e20/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x134/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 0 UID: 0 PID: 6045 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
=====================================================


---
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.

Re: [syzbot] [bridge?] KMSAN: uninit-value in netif_skb_features (4)

[syzbot]

Hello,

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

Reported-by: syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com
Tested-by: syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com

Tested on:

commit:         4ae12d8b Merge tag 'kbuild-fixes-7.0-2' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17616b5a580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=242f02fcd3fbc8f3
dashboard link: https://syzkaller.appspot.com/bug?extid=1543a7d954d9c6d00407
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1789d8d6580000

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

Re: [syzbot] [bridge?] KMSAN: uninit-value in netif_skb_features (4)

[syzbot]

Hello,

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

Reported-by: syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com
Tested-by: syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com

Tested on:

commit:         c23719ab Merge tag 'x86-urgent-2026-03-08' of git://gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17af0806580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=242f02fcd3fbc8f3
dashboard link: https://syzkaller.appspot.com/bug?extid=1543a7d954d9c6d00407
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=101d3fe6580000

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

Re: [syzbot] [bridge?] KMSAN: uninit-value in netif_skb_features (4)

[syzbot]

Hello,

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

=====================================================
BUG: KMSAN: uninit-value in gso_features_check net/core/dev.c:3816 [inline]
BUG: KMSAN: uninit-value in netif_skb_features+0x15fc/0x1a50 net/core/dev.c:3841
 gso_features_check net/core/dev.c:3816 [inline]
 netif_skb_features+0x15fc/0x1a50 net/core/dev.c:3841
 validate_xmit_skb+0xb6/0x2400 net/core/dev.c:4016
 validate_xmit_skb_list+0xd4/0x320 net/core/dev.c:4078
 sch_direct_xmit+0xd4/0xcf0 net/sched/sch_generic.c:332
 __dev_xmit_skb net/core/dev.c:4192 [inline]
 __dev_queue_xmit+0x301d/0x5980 net/core/dev.c:4808
 dev_queue_xmit include/linux/netdevice.h:3384 [inline]
 packet_xmit+0x8f/0x710 net/packet/af_packet.c:275
 packet_snd net/packet/af_packet.c:3076 [inline]
 packet_sendmsg+0x91d9/0xa320 net/packet/af_packet.c:3108
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xf37/0xfd0 net/socket.c:2592
 ___sys_sendmsg+0x271/0x3b0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x211/0x3e0 net/socket.c:2681
 x64_sys_call+0x1e20/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x134/0xf80 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:4549 [inline]
 slab_alloc_node mm/slub.c:4869 [inline]
 kmem_cache_alloc_node_noprof+0x3cd/0x12d0 mm/slub.c:4921
 kmalloc_reserve net/core/skbuff.c:613 [inline]
 __alloc_skb+0x855/0x1190 net/core/skbuff.c:713
 alloc_skb include/linux/skbuff.h:1383 [inline]
 alloc_skb_with_frags+0xc5/0xa60 net/core/skbuff.c:6763
 sock_alloc_send_pskb+0xacb/0xc60 net/core/sock.c:2995
 packet_alloc_skb net/packet/af_packet.c:2926 [inline]
 packet_snd net/packet/af_packet.c:3019 [inline]
 packet_sendmsg+0x7477/0xa320 net/packet/af_packet.c:3108
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xf37/0xfd0 net/socket.c:2592
 ___sys_sendmsg+0x271/0x3b0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x211/0x3e0 net/socket.c:2681
 x64_sys_call+0x1e20/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x134/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 UID: 0 PID: 6599 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/27/2026
=====================================================


Tested on:

commit:         80234b5a Merge tag 'rproc-v7.0-fixes' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=109504d6580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=242f02fcd3fbc8f3
dashboard link: https://syzkaller.appspot.com/bug?extid=1543a7d954d9c6d00407
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1241b75a580000

Re: [syzbot] [bridge?] KMSAN: uninit-value in netif_skb_features (4)

[syzbot]

Hello,

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

Reported-by: syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com
Tested-by: syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com

Tested on:

commit:         80234b5a Merge tag 'rproc-v7.0-fixes' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16e6f3aa580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=242f02fcd3fbc8f3
dashboard link: https://syzkaller.appspot.com/bug?extid=1543a7d954d9c6d00407
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=157aef5a580000

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