syzbot


KMSAN: uninit-value in nf_flow_offload_inet_hook (2)

Status: upstream: reported C repro on 2025/07/07 12:41
Subsystems: netfilter
[Documentation on labels]
Reported-by: syzbot+bf6ed459397e307c3ad2@syzkaller.appspotmail.com
Fix commit: 18cdb3d982da netfilter: flowtable: account for Ethernet header in nf_flow_pppoe_proto()
Patched on: [ci-qemu-gce-upstream-auto ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-snapshot-upstream-root ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-linux-next-kasan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci-upstream-rust-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce], missing on: [ci-qemu-native-arm64-kvm ci-qemu2-riscv64 ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci2-upstream-usb]
First crash: 9d02h, last: 6d02h
Discussions (2)
Title Replies (including bot) Last reply
[PATCH net] netfilter: flowtable: account for Ethernet header in nf_flow_pppoe_proto() 3 (3) 2025/07/11 00:30
[syzbot] [netfilter?] KMSAN: uninit-value in nf_flow_offload_inet_hook (2) 0 (1) 2025/07/07 12:41
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KMSAN: uninit-value in nf_flow_offload_inet_hook netfilter 7 4 330d 340d 28/29 fixed on 2024/10/03 15:25
Last patch testing requests (1)
Created Duration User Patch Repo Result
2025/07/07 09:44 34m edumazet@google.com patch upstream OK log

Sample crash report:
=====================================================
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
=====================================================

Crashes (13):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/07 00:00 upstream 1f988d0788f5 4f67c4ae .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in nf_flow_offload_inet_hook
2025/07/09 17:36 upstream 733923397fd9 f4e5e155 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in nf_flow_offload_inet_hook
2025/07/09 17:36 upstream 733923397fd9 f4e5e155 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in nf_flow_offload_inet_hook
2025/07/09 06:26 upstream d006330be3f7 abade794 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in nf_flow_offload_inet_hook
2025/07/06 19:21 upstream 1f988d0788f5 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in nf_flow_offload_inet_hook
2025/07/06 17:21 upstream 1f988d0788f5 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in nf_flow_offload_inet_hook
2025/07/06 17:21 upstream 1f988d0788f5 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in nf_flow_offload_inet_hook
2025/07/09 06:48 upstream d006330be3f7 abade794 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386-root KMSAN: uninit-value in nf_flow_offload_inet_hook
2025/07/09 06:46 upstream d006330be3f7 abade794 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386-root KMSAN: uninit-value in nf_flow_offload_inet_hook
2025/07/06 19:01 upstream 1f988d0788f5 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386-root KMSAN: uninit-value in nf_flow_offload_inet_hook
2025/07/06 19:01 upstream 1f988d0788f5 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386-root KMSAN: uninit-value in nf_flow_offload_inet_hook
2025/07/06 18:27 upstream 1f988d0788f5 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386-root KMSAN: uninit-value in nf_flow_offload_inet_hook
2025/07/06 18:27 upstream 1f988d0788f5 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386-root KMSAN: uninit-value in nf_flow_offload_inet_hook
* Struck through repros no longer work on HEAD.