[syzbot] [netfilter?] KMSAN: uninit-value in nf_flow_offload_inet_hook (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    1f988d0788f5 Merge tag 'hid-for-linus-2025070502' of git:/..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=162bef70580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=aa9af7332485152e
dashboard link: https://syzkaller.appspot.com/bug?extid=bf6ed459397e307c3ad2
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1433e582580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16a6828c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/84da6415798d/disk-1f988d07.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/62abf67637e4/vmlinux-1f988d07.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0bb719d426ed/bzImage-1f988d07.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bf6ed459397e307c3ad2@xxxxxxxxxxxxxxxxxxxxxxxxx

=====================================================
BUG: KMSAN: uninit-value in nf_flow_offload_inet_hook+0x7e4/0x940 net/netfilter/nf_flow_table_inet.c:27
 nf_flow_offload_inet_hook+0x7e4/0x940 net/netfilter/nf_flow_table_inet.c:27
 nf_hook_entry_hookfn include/linux/netfilter.h:157 [inline]
 nf_hook_slow+0xe1/0x3d0 net/netfilter/core.c:623
 nf_hook_ingress include/linux/netfilter_netdev.h:34 [inline]
 nf_ingress net/core/dev.c:5742 [inline]
 __netif_receive_skb_core+0x4aff/0x70c0 net/core/dev.c:5837
 __netif_receive_skb_one_core net/core/dev.c:5975 [inline]
 __netif_receive_skb+0xcc/0xac0 net/core/dev.c:6090
 netif_receive_skb_internal net/core/dev.c:6176 [inline]
 netif_receive_skb+0x57/0x630 net/core/dev.c:6235
 tun_rx_batched+0x1df/0x980 drivers/net/tun.c:1485
 tun_get_user+0x4ee0/0x6b40 drivers/net/tun.c:1938
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1984
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0xb4b/0x1580 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+0x38c3/0x3db0 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:4154 [inline]
 slab_alloc_node mm/slub.c:4197 [inline]
 kmem_cache_alloc_node_noprof+0x818/0xf00 mm/slub.c:4249
 kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:579
 __alloc_skb+0x347/0x7d0 net/core/skbuff.c:670
 alloc_skb include/linux/skbuff.h:1336 [inline]
 alloc_skb_with_frags+0xc5/0xa60 net/core/skbuff.c:6665
 sock_alloc_send_pskb+0xad8/0xc70 net/core/sock.c:2999
 tun_alloc_skb drivers/net/tun.c:1461 [inline]
 tun_get_user+0x1019/0x6b40 drivers/net/tun.c:1782
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1984
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0xb4b/0x1580 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+0x38c3/0x3db0 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

CPU: 0 UID: 0 PID: 5890 Comm: syz-executor738 Not tainted 6.16.0-rc4-syzkaller-00324-g1f988d0788f5 #0 PREEMPT(undef) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
=====================================================


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