KMSAN: uninit-value in ip6table_mangle_hook (3)

Status: upstream: reported C repro on 2024/11/22 14:42
Subsystems: netfilter
[Documentation on labels]
Reported-by: syzbot+6023ea32e206eef7920a@syzkaller.appspotmail.com
First crash: 628d, last: 98d
▶ ▼ ✨ AI Jobs (6)
ID Workflow Result Correct Bug Created Started Finished Revision Error
39f080bf assessment-security 💥 KMSAN: uninit-value in ip6table_mangle_hook (3) 2026/07/05 07:35 2026/07/05 07:35 2026/07/05 07:55 93f57954 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/7da674412b4e0984a7...
truncated to first 200 bytes; open job for full error
18a355b7 assessment-security 💥 KMSAN: uninit-value in ip6table_mangle_hook (3) 2026/06/18 07:21 2026/06/18 07:21 2026/06/18 07:43 b62b3ded 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/7da674412b4e0984a7...
truncated to first 200 bytes; open job for full error
4fb978f2 assessment-security 💥 KMSAN: uninit-value in ip6table_mangle_hook (3) 2026/06/10 03:06 2026/06/10 03:06 2026/06/10 03:30 c36c07f6 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/7da674412b4e0984a7...
truncated to first 200 bytes; open job for full error
79daa960 assessment-security 💥 KMSAN: uninit-value in ip6table_mangle_hook (3) 2026/06/04 05:51 2026/06/04 05:51 2026/06/04 06:07 62fe1528 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/7da674412b4e0984a7...
truncated to first 200 bytes; open job for full error
4762241f assessment-security 💥 KMSAN: uninit-value in ip6table_mangle_hook (3) 2026/06/02 02:27 2026/06/02 02:27 2026/06/02 02:56 386cc6da 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/7da674412b4e0984a7...
truncated to first 200 bytes; open job for full error
28402ec7 assessment-security 💥 KMSAN: uninit-value in ip6table_mangle_hook (3) 2026/05/21 03:22 2026/05/21 03:22 2026/05/21 03:51 cf874a1c 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/7da674412b4e0984a7...
truncated to first 200 bytes; open job for full error
▶ ▼ Discussions (11)
Title Replies (including bot) Last reply
[syzbot] Monthly netfilter report (Apr 2026) 0 (1) 2026/04/29 20:32
[syzbot] Monthly netfilter report (Mar 2026) 0 (1) 2026/03/31 08:07
[PATCH net v3] ip6_gre: use skb_vlan_inet_prepare() instead of pskb_inet_may_pull() 5 (5) 2026/01/20 00:01
[PATCH v2 net] ip6_gre: use skb_vlan_inet_prepare() instead of pskb_inet_may_pull() 11 (11) 2026/01/12 15:24
[PATCH net] ip6_gre: use skb_vlan_inet_prepare() instead of pskb_inet_may_pull() 3 (3) 2026/01/05 20:50
[PATCH] ip6_tunnel: Fix uninit-value in ip6_tnl_xmit 5 (5) 2026/01/05 09:35
[syzbot] Monthly netfilter report (Jul 2025) 0 (1) 2025/07/20 09:04
[syzbot] Monthly netfilter report (Apr 2025) 0 (1) 2025/04/17 08:38
[syzbot] Monthly netfilter report (Feb 2025) 0 (1) 2025/02/13 12:34
[syzbot] [netfilter?] KMSAN: uninit-value in ip6table_mangle_hook (3) 0 (6) 2024/12/15 02:34
[syzbot] Monthly netfilter report (Dec 2024) 0 (1) 2024/12/13 13:16
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KMSAN: uninit-value in ip6table_mangle_hook netfilter 7 C 601 3001d 3032d 5/29 fixed on 2018/05/08 18:30
upstream KMSAN: uninit-value in ip6table_mangle_hook (2) netfilter 7 10 1847d 1925d 0/29 auto-closed as invalid on 2021/10/03 15:10
▶ ▼ Last patch testing requests (15)
Created Duration User Patch Repo Result
2026/06/29 00:05 33m retest repro upstream error
2026/06/06 07:49 34m retest repro upstream log
2026/04/19 22:17 32m retest repro upstream report log
2026/04/19 22:02 27m retest repro upstream report log
2026/03/28 07:12 21m retest repro upstream report log
2026/02/08 21:10 21m retest repro upstream report log
2026/01/17 06:09 34m retest repro upstream report log
2025/11/30 12:12 22m retest repro upstream report log
2025/11/07 18:31 21m retest repro upstream report log
2025/09/21 07:59 1h30m retest repro upstream report log
2024/12/15 02:34 35m mazin@getstate.dev patch upstream OK log
2024/12/14 22:21 20m mazin@getstate.dev upstream report log
2024/12/14 22:16 1h09m mazin@getstate.dev patch upstream OK log
2024/12/03 15:28 21m dmantipov@yandex.ru patch https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git cdd30ebb1b9f36159d66f088b61aee264e649d7a report log
2024/12/03 13:28 23m dmantipov@yandex.ru patch https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git cdd30ebb1b9f36159d66f088b61aee264e649d7a report log

Sample crash report:
=====================================================
BUG: KMSAN: uninit-value in ip6t_mangle_out net/ipv6/netfilter/ip6table_mangle.c:56 [inline]
BUG: KMSAN: uninit-value in ip6table_mangle_hook+0x97d/0x9c0 net/ipv6/netfilter/ip6table_mangle.c:72
 ip6t_mangle_out net/ipv6/netfilter/ip6table_mangle.c:56 [inline]
 ip6table_mangle_hook+0x97d/0x9c0 net/ipv6/netfilter/ip6table_mangle.c:72
 nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline]
 nf_hook_slow+0xf4/0x400 net/netfilter/core.c:626
 nf_hook include/linux/netfilter.h:269 [inline]
 __ip6_local_out+0x5ac/0x640 net/ipv6/output_core.c:143
 ip6_local_out+0x4c/0x210 net/ipv6/output_core.c:153
 ip6tunnel_xmit+0x129/0x460 include/net/ip6_tunnel.h:161
 ip6_tnl_xmit+0x341a/0x3860 net/ipv6/ip6_tunnel.c:1281
 __gre6_xmit+0x14b9/0x1550 net/ipv6/ip6_gre.c:815
 ip6gre_xmit_ipv4 net/ipv6/ip6_gre.c:839 [inline]
 ip6gre_tunnel_xmit+0x18f7/0x2030 net/ipv6/ip6_gre.c:922
 __netdev_start_xmit include/linux/netdevice.h:4928 [inline]
 netdev_start_xmit include/linux/netdevice.h:4937 [inline]
 xmit_one net/core/dev.c:3588 [inline]
 dev_hard_start_xmit+0x247/0xa20 net/core/dev.c:3604
 sch_direct_xmit+0x399/0xd40 net/sched/sch_generic.c:343
 __dev_xmit_skb net/core/dev.c:3825 [inline]
 __dev_queue_xmit+0x2fcf/0x56d0 net/core/dev.c:4398
 dev_queue_xmit include/linux/netdevice.h:3094 [inline]
 packet_xmit+0x9c/0x6c0 net/packet/af_packet.c:276
 packet_snd net/packet/af_packet.c:3145 [inline]
 packet_sendmsg+0x908b/0xa370 net/packet/af_packet.c:3177
 sock_sendmsg_nosec net/socket.c:729 [inline]
 __sock_sendmsg+0x30f/0x380 net/socket.c:744
 __sys_sendto+0x645/0x7f0 net/socket.c:2214
 __do_sys_sendto net/socket.c:2226 [inline]
 __se_sys_sendto net/socket.c:2222 [inline]
 __x64_sys_sendto+0x125/0x1d0 net/socket.c:2222
 x64_sys_call+0x3373/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:45
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was stored to memory at:
 ip6_tnl_xmit+0x34f7/0x3860 net/ipv6/ip6_tunnel.c:1277
 __gre6_xmit+0x14b9/0x1550 net/ipv6/ip6_gre.c:815
 ip6gre_xmit_ipv4 net/ipv6/ip6_gre.c:839 [inline]
 ip6gre_tunnel_xmit+0x18f7/0x2030 net/ipv6/ip6_gre.c:922
 __netdev_start_xmit include/linux/netdevice.h:4928 [inline]
 netdev_start_xmit include/linux/netdevice.h:4937 [inline]
 xmit_one net/core/dev.c:3588 [inline]
 dev_hard_start_xmit+0x247/0xa20 net/core/dev.c:3604
 sch_direct_xmit+0x399/0xd40 net/sched/sch_generic.c:343
 __dev_xmit_skb net/core/dev.c:3825 [inline]
 __dev_queue_xmit+0x2fcf/0x56d0 net/core/dev.c:4398
 dev_queue_xmit include/linux/netdevice.h:3094 [inline]
 packet_xmit+0x9c/0x6c0 net/packet/af_packet.c:276
 packet_snd net/packet/af_packet.c:3145 [inline]
 packet_sendmsg+0x908b/0xa370 net/packet/af_packet.c:3177
 sock_sendmsg_nosec net/socket.c:729 [inline]
 __sock_sendmsg+0x30f/0x380 net/socket.c:744
 __sys_sendto+0x645/0x7f0 net/socket.c:2214
 __do_sys_sendto net/socket.c:2226 [inline]
 __se_sys_sendto net/socket.c:2222 [inline]
 __x64_sys_sendto+0x125/0x1d0 net/socket.c:2222
 x64_sys_call+0x3373/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:45
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4091 [inline]
 slab_alloc_node mm/slub.c:4134 [inline]
 __do_kmalloc_node mm/slub.c:4263 [inline]
 __kmalloc_node_track_caller_noprof+0x6c7/0xf90 mm/slub.c:4283
 kmalloc_reserve+0x23e/0x4a0 net/core/skbuff.c:609
 pskb_expand_head+0x226/0x1a60 net/core/skbuff.c:2275
 skb_realloc_headroom+0x140/0x2b0 net/core/skbuff.c:2355
 ip6_tnl_xmit+0x2106/0x3860 net/ipv6/ip6_tunnel.c:1227
 __gre6_xmit+0x14b9/0x1550 net/ipv6/ip6_gre.c:815
 ip6gre_xmit_ipv4 net/ipv6/ip6_gre.c:839 [inline]
 ip6gre_tunnel_xmit+0x18f7/0x2030 net/ipv6/ip6_gre.c:922
 __netdev_start_xmit include/linux/netdevice.h:4928 [inline]
 netdev_start_xmit include/linux/netdevice.h:4937 [inline]
 xmit_one net/core/dev.c:3588 [inline]
 dev_hard_start_xmit+0x247/0xa20 net/core/dev.c:3604
 sch_direct_xmit+0x399/0xd40 net/sched/sch_generic.c:343
 __dev_xmit_skb net/core/dev.c:3825 [inline]
 __dev_queue_xmit+0x2fcf/0x56d0 net/core/dev.c:4398
 dev_queue_xmit include/linux/netdevice.h:3094 [inline]
 packet_xmit+0x9c/0x6c0 net/packet/af_packet.c:276
 packet_snd net/packet/af_packet.c:3145 [inline]
 packet_sendmsg+0x908b/0xa370 net/packet/af_packet.c:3177
 sock_sendmsg_nosec net/socket.c:729 [inline]
 __sock_sendmsg+0x30f/0x380 net/socket.c:744
 __sys_sendto+0x645/0x7f0 net/socket.c:2214
 __do_sys_sendto net/socket.c:2226 [inline]
 __se_sys_sendto net/socket.c:2222 [inline]
 __x64_sys_sendto+0x125/0x1d0 net/socket.c:2222
 x64_sys_call+0x3373/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:45
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 UID: 0 PID: 5819 Comm: syz-executor359 Not tainted 6.12.0-rc6-syzkaller-00077-g2e1b3cc9d7f7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
=====================================================

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/11/06 11:13 upstream 2e1b3cc9d7f7 3a465482 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ip6table_mangle_hook
2024/11/06 06:19 upstream 2e1b3cc9d7f7 3a465482 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ip6table_mangle_hook
2025/02/04 17:44 upstream 0de63bb7d919 8f267cef .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ip6table_mangle_hook
2024/11/30 05:22 upstream 509f806f7f70 68914665 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ip6table_mangle_hook
2024/11/30 05:21 upstream 509f806f7f70 68914665 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ip6table_mangle_hook
2024/11/06 02:06 upstream 2e1b3cc9d7f7 3a465482 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ip6table_mangle_hook
2024/11/06 02:06 upstream 2e1b3cc9d7f7 3a465482 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ip6table_mangle_hook
2024/11/30 17:51 upstream 2ba9f676d0a2 68914665 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386-root KMSAN: uninit-value in ip6table_mangle_hook
2024/11/30 17:50 upstream 2ba9f676d0a2 68914665 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386-root KMSAN: uninit-value in ip6table_mangle_hook
2024/11/30 17:46 upstream 2ba9f676d0a2 68914665 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386-root KMSAN: uninit-value in ip6table_mangle_hook
2024/11/06 07:43 upstream 2e1b3cc9d7f7 3a465482 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386-root KMSAN: uninit-value in ip6table_mangle_hook
* Struck through repros no longer work on HEAD.