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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e406d57be7bd Merge tag 'mm-nonmm-stable-2025-10-02-15-29' ..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=144ad942580000
kernel config: https://syzkaller.appspot.com/x/.config?x=50fb29d81ff5a3df
dashboard link: https://syzkaller.appspot.com/bug?extid=1543a7d954d9c6d00407
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7aa074b1bf56/disk-e406d57b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4c8a46bed2ec/vmlinux-e406d57b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9ed66e725466/bzImage-e406d57b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1543a7...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in netif_skb_features+0x115b/0x2160 net/core/dev.c:3825
netif_skb_features+0x115b/0x2160 net/core/dev.c:3825
validate_xmit_skb+0xb6/0x1d50 net/core/dev.c:3985
__dev_queue_xmit+0x23f8/0x5e60 net/core/dev.c:4755
dev_queue_xmit include/linux/netdevice.h:3365 [inline]
hsr_xmit net/hsr/hsr_forward.c:430 [inline]
hsr_forward_do net/hsr/hsr_forward.c:571 [inline]
hsr_forward_skb+0x2162/0x3c40 net/hsr/hsr_forward.c:733
hsr_handle_frame+0xd6d/0x11a0 net/hsr/hsr_slave.c:81
__netif_receive_skb_core+0x2040/0x7150 net/core/dev.c:5966
__netif_receive_skb_list_core+0x2f1/0x16b0 net/core/dev.c:6154
__netif_receive_skb_list net/core/dev.c:6221 [inline]
netif_receive_skb_list_internal+0xee7/0x1530 net/core/dev.c:6312
gro_normal_list include/net/gro.h:524 [inline]
gro_flush_normal include/net/gro.h:532 [inline]
napi_complete_done+0x3fb/0x7d0 net/core/dev.c:6681
gro_cell_poll+0x2c9/0x310 net/core/gro_cells.c:66
__napi_poll+0xda/0x8a0 net/core/dev.c:7594
napi_poll net/core/dev.c:7657 [inline]
net_rx_action+0xbc8/0x1c30 net/core/dev.c:7784
handle_softirqs+0x169/0x6e0 kernel/softirq.c:622
__do_softirq+0x14/0x1b kernel/softirq.c:656
do_softirq+0x99/0x100 kernel/softirq.c:523
__local_bh_enable_ip+0xa1/0xb0 kernel/softirq.c:450
local_bh_enable include/linux/bottom_half.h:33 [inline]
tun_rx_batched+0x889/0x980 drivers/net/tun.c:-1
tun_get_user+0x5d60/0x6d70 drivers/net/tun.c:1953
tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1999
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0xbdf/0x15d0 fs/read_write.c:686
ksys_write fs/read_write.c:738 [inline]
__do_sys_write fs/read_write.c:749 [inline]
__se_sys_write fs/read_write.c:746 [inline]
__x64_sys_write+0x1fb/0x4d0 fs/read_write.c:746
x64_sys_call+0x3014/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:2
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd9/0x210 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:4953 [inline]
slab_alloc_node mm/slub.c:5245 [inline]
kmem_cache_alloc_node_noprof+0x989/0x16b0 mm/slub.c:5297
kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:579
__alloc_skb+0x347/0x7d0 net/core/skbuff.c:670
__pskb_copy_fclone+0xcc/0x14d0 net/core/skbuff.c:2164
__pskb_copy include/linux/skbuff.h:1447 [inline]
hsr_create_tagged_frame+0x32c/0x11b0 net/hsr/hsr_forward.c:340
hsr_forward_do net/hsr/hsr_forward.c:-1 [inline]
hsr_forward_skb+0x16a4/0x3c40 net/hsr/hsr_forward.c:733
hsr_handle_frame+0xd6d/0x11a0 net/hsr/hsr_slave.c:81
__netif_receive_skb_core+0x2040/0x7150 net/core/dev.c:5966
__netif_receive_skb_list_core+0x2f1/0x16b0 net/core/dev.c:6154
__netif_receive_skb_list net/core/dev.c:6221 [inline]
netif_receive_skb_list_internal+0xee7/0x1530 net/core/dev.c:6312
gro_normal_list include/net/gro.h:524 [inline]
gro_flush_normal include/net/gro.h:532 [inline]
napi_complete_done+0x3fb/0x7d0 net/core/dev.c:6681
gro_cell_poll+0x2c9/0x310 net/core/gro_cells.c:66
__napi_poll+0xda/0x8a0 net/core/dev.c:7594
napi_poll net/core/dev.c:7657 [inline]
net_rx_action+0xbc8/0x1c30 net/core/dev.c:7784
handle_softirqs+0x169/0x6e0 kernel/softirq.c:622
__do_softirq+0x14/0x1b kernel/softirq.c:656

CPU: 1 UID: 0 PID: 11876 Comm: syz.2.2011 Not tainted syzkaller #0 PREEMPT(none)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
=====================================================


---
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[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+1543a7...@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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