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

[syzbot <syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com>]

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
=====================================================


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