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Message-ID: <693613a3.a70a0220.38f243.0071.GAE@google.com>
Date: Sun, 07 Dec 2025 15:54:11 -0800
From: syzbot ci <syzbot+ci57ebb75c98bab786@...kaller.appspotmail.com>
To: coreteam@...filter.org, davem@...emloft.net, dsahern@...nel.org,
edumazet@...gle.com, fw@...len.de, horms@...nel.org, kadlec@...filter.org,
kuba@...nel.org, linux-kselftest@...r.kernel.org, lorenzo@...nel.org,
netdev@...r.kernel.org, netfilter-devel@...r.kernel.org, pabeni@...hat.com,
pablo@...filter.org, phil@....cc, shuah@...nel.org
Cc: syzbot@...ts.linux.dev, syzkaller-bugs@...glegroups.com
Subject: [syzbot ci] Re: Add IP6IP6 flowtable SW acceleration
syzbot ci has tested the following series
[v1] Add IP6IP6 flowtable SW acceleration
https://lore.kernel.org/all/20251207-b4-flowtable-offload-ip6ip6-v1-0-18e3ab7f748c@kernel.org
* [PATCH nf-next 1/5] netfilter: Introduce tunnel metadata info in nf_flowtable_ctx struct
* [PATCH nf-next 2/5] netfilter: Modify nf_flow_skb_encap_protocol() to return int intead of bool
* [PATCH nf-next 3/5] netfilter: flowtable: Add IP6IP6 rx sw acceleration
* [PATCH nf-next 4/5] netfilter: flowtable: Add IP6IP6 tx sw acceleration
* [PATCH nf-next 5/5] selftests: netfilter: nft_flowtable.sh: Add IP6IP6 flowtable selftest
and found the following issues:
* KASAN: slab-use-after-free Read in nf_flow_skb_encap_protocol
* general protection fault in ipv6_frag_rcv
* general protection fault in nf_flow_offload_ipv6_hook
Full report is available here:
https://ci.syzbot.org/series/24632ec9-06ab-4e09-8015-19822d83c6a9
***
KASAN: slab-use-after-free Read in nf_flow_skb_encap_protocol
tree: nf-next
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/netfilter/nf-next.git
base: ff736a286116d462a4067ba258fa351bc0b4ed80
arch: amd64
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
config: https://ci.syzbot.org/builds/833219cc-e7e2-437d-b31c-1eb3666c1e93/config
C repro: https://ci.syzbot.org/findings/afcab565-801f-4cde-a1c5-b1d327537871/c_repro
syz repro: https://ci.syzbot.org/findings/afcab565-801f-4cde-a1c5-b1d327537871/syz_repro
==================================================================
BUG: KASAN: slab-use-after-free in nf_flow_ip6_tunnel_proto net/netfilter/nf_flow_table_ip.c:388 [inline]
BUG: KASAN: slab-use-after-free in nf_flow_skb_encap_protocol+0x13a2/0x1540 net/netfilter/nf_flow_table_ip.c:438
Read of size 2 at addr ffff888175605eb6 by task syz.1.20/6010
CPU: 1 UID: 0 PID: 6010 Comm: syz.1.20 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xca/0x240 mm/kasan/report.c:482
kasan_report+0x118/0x150 mm/kasan/report.c:595
nf_flow_ip6_tunnel_proto net/netfilter/nf_flow_table_ip.c:388 [inline]
nf_flow_skb_encap_protocol+0x13a2/0x1540 net/netfilter/nf_flow_table_ip.c:438
nf_flow_offload_ipv6_lookup net/netfilter/nf_flow_table_ip.c:1074 [inline]
nf_flow_offload_ipv6_hook+0x13c/0x32a0 net/netfilter/nf_flow_table_ip.c:1102
nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
nf_hook_slow+0xc5/0x220 net/netfilter/core.c:623
nf_hook_ingress include/linux/netfilter_netdev.h:34 [inline]
nf_ingress net/core/dev.c:5900 [inline]
__netif_receive_skb_core+0x241c/0x2f90 net/core/dev.c:5996
__netif_receive_skb_one_core net/core/dev.c:6135 [inline]
__netif_receive_skb+0x72/0x380 net/core/dev.c:6250
netif_receive_skb_internal net/core/dev.c:6336 [inline]
netif_receive_skb+0x1cb/0x790 net/core/dev.c:6395
tun_rx_batched+0x1b9/0x730 drivers/net/tun.c:1485
tun_get_user+0x2b65/0x3e90 drivers/net/tun.c:1953
tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1999
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c9/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f53b9d8f7c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f53babe6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f53b9fe6090 RCX: 00007f53b9d8f7c9
RDX: 000000000000fdef RSI: 0000200000000340 RDI: 0000000000000003
RBP: 00007f53b9df297f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f53b9fe6128 R14: 00007f53b9fe6090 R15: 00007ffc1b120a08
</TASK>
Allocated by task 6010:
kasan_save_stack mm/kasan/common.c:56 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
unpoison_slab_object mm/kasan/common.c:342 [inline]
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:368
kasan_slab_alloc include/linux/kasan.h:252 [inline]
slab_post_alloc_hook mm/slub.c:4978 [inline]
slab_alloc_node mm/slub.c:5288 [inline]
kmem_cache_alloc_node_noprof+0x433/0x710 mm/slub.c:5340
__alloc_skb+0x255/0x430 net/core/skbuff.c:679
alloc_skb include/linux/skbuff.h:1383 [inline]
alloc_skb_with_frags+0xca/0x890 net/core/skbuff.c:6712
sock_alloc_send_pskb+0x84d/0x980 net/core/sock.c:2995
tun_alloc_skb drivers/net/tun.c:1461 [inline]
tun_get_user+0xa43/0x3e90 drivers/net/tun.c:1794
tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1999
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c9/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 6010:
kasan_save_stack mm/kasan/common.c:56 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
__kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:587
kasan_save_free_info mm/kasan/kasan.h:406 [inline]
poison_slab_object mm/kasan/common.c:252 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
kasan_slab_free include/linux/kasan.h:234 [inline]
slab_free_hook mm/slub.c:2543 [inline]
slab_free mm/slub.c:6642 [inline]
kmem_cache_free+0x19b/0x690 mm/slub.c:6752
kfree_skb_reason include/linux/skbuff.h:1322 [inline]
kfree_skb include/linux/skbuff.h:1331 [inline]
dst_discard_out+0x1c/0x30 net/core/dst.c:32
nf_flow_ip6_tunnel_proto net/netfilter/nf_flow_table_ip.c:383 [inline]
nf_flow_skb_encap_protocol+0x9c2/0x1540 net/netfilter/nf_flow_table_ip.c:438
nf_flow_offload_ipv6_lookup net/netfilter/nf_flow_table_ip.c:1074 [inline]
nf_flow_offload_ipv6_hook+0x13c/0x32a0 net/netfilter/nf_flow_table_ip.c:1102
nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
nf_hook_slow+0xc5/0x220 net/netfilter/core.c:623
nf_hook_ingress include/linux/netfilter_netdev.h:34 [inline]
nf_ingress net/core/dev.c:5900 [inline]
__netif_receive_skb_core+0x241c/0x2f90 net/core/dev.c:5996
__netif_receive_skb_one_core net/core/dev.c:6135 [inline]
__netif_receive_skb+0x72/0x380 net/core/dev.c:6250
netif_receive_skb_internal net/core/dev.c:6336 [inline]
netif_receive_skb+0x1cb/0x790 net/core/dev.c:6395
tun_rx_batched+0x1b9/0x730 drivers/net/tun.c:1485
tun_get_user+0x2b65/0x3e90 drivers/net/tun.c:1953
tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1999
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c9/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff888175605e00
which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 182 bytes inside of
freed 240-byte region [ffff888175605e00, ffff888175605ef0)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x175604
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x57ff00000000040(head|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000040 ffff8881036c4a00 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080150015 00000000f5000000 0000000000000000
head: 057ff00000000040 ffff8881036c4a00 dead000000000122 0000000000000000
head: 0000000000000000 0000000080150015 00000000f5000000 0000000000000000
head: 057ff00000000001 ffffea0005d58101 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5922, tgid 5922 (syz-executor), ts 68256102142, free_ts 61484167308
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x234/0x290 mm/page_alloc.c:1845
prep_new_page mm/page_alloc.c:1853 [inline]
get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3879
__alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5178
alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
alloc_slab_page mm/slub.c:3059 [inline]
allocate_slab+0x96/0x350 mm/slub.c:3232
new_slab mm/slub.c:3286 [inline]
___slab_alloc+0xf56/0x1990 mm/slub.c:4655
__slab_alloc+0x65/0x100 mm/slub.c:4778
__slab_alloc_node mm/slub.c:4854 [inline]
slab_alloc_node mm/slub.c:5276 [inline]
kmem_cache_alloc_node_noprof+0x4c5/0x710 mm/slub.c:5340
__alloc_skb+0x255/0x430 net/core/skbuff.c:679
alloc_skb include/linux/skbuff.h:1383 [inline]
nlmsg_new include/net/netlink.h:1055 [inline]
inet_ifmcaddr_notify+0x7e/0x150 net/ipv4/igmp.c:1481
____ip_mc_inc_group+0x9b8/0xde0 net/ipv4/igmp.c:1564
__ip_mc_inc_group net/ipv4/igmp.c:1573 [inline]
ip_mc_inc_group net/ipv4/igmp.c:1579 [inline]
ip_mc_up+0x125/0x300 net/ipv4/igmp.c:1880
inetdev_event+0xfb3/0x15b0 net/ipv4/devinet.c:1630
notifier_call_chain+0x1b6/0x3e0 kernel/notifier.c:85
call_netdevice_notifiers_extack net/core/dev.c:2268 [inline]
call_netdevice_notifiers net/core/dev.c:2282 [inline]
__dev_notify_flags+0x18d/0x2e0 net/core/dev.c:-1
netif_change_flags+0xe8/0x1a0 net/core/dev.c:9802
page last free pid 5811 tgid 5811 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1394 [inline]
__free_frozen_pages+0xbc4/0xd30 mm/page_alloc.c:2901
__slab_free+0x2e7/0x390 mm/slub.c:5970
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x97/0x140 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:352
kasan_slab_alloc include/linux/kasan.h:252 [inline]
slab_post_alloc_hook mm/slub.c:4978 [inline]
slab_alloc_node mm/slub.c:5288 [inline]
kmem_cache_alloc_noprof+0x367/0x6e0 mm/slub.c:5295
ptlock_alloc+0x20/0x70 mm/memory.c:7302
ptlock_init include/linux/mm.h:3059 [inline]
pagetable_pte_ctor include/linux/mm.h:3113 [inline]
__pte_alloc_one_noprof include/asm-generic/pgalloc.h:78 [inline]
pte_alloc_one+0x7a/0x310 arch/x86/mm/pgtable.c:18
__do_fault+0xd1/0x390 mm/memory.c:5276
do_shared_fault mm/memory.c:5780 [inline]
do_fault mm/memory.c:5854 [inline]
do_pte_missing mm/memory.c:4362 [inline]
handle_pte_fault mm/memory.c:6195 [inline]
__handle_mm_fault+0x1847/0x5400 mm/memory.c:6336
handle_mm_fault+0x40a/0x8e0 mm/memory.c:6505
do_user_addr_fault+0xa7c/0x1380 arch/x86/mm/fault.c:1336
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
Memory state around the buggy address:
ffff888175605d80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888175605e00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888175605e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
^
ffff888175605f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888175605f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
***
general protection fault in ipv6_frag_rcv
tree: nf-next
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/netfilter/nf-next.git
base: ff736a286116d462a4067ba258fa351bc0b4ed80
arch: amd64
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
config: https://ci.syzbot.org/builds/833219cc-e7e2-437d-b31c-1eb3666c1e93/config
C repro: https://ci.syzbot.org/findings/bac8a298-33d8-4b3a-9f63-a0a2373aaab2/c_repro
syz repro: https://ci.syzbot.org/findings/bac8a298-33d8-4b3a-9f63-a0a2373aaab2/syz_repro
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 UID: 0 PID: 5982 Comm: syz.1.20 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:dst_dev include/net/dst.h:571 [inline]
RIP: 0010:skb_dst_dev include/net/dst.h:586 [inline]
RIP: 0010:skb_dst_dev_net include/net/dst.h:596 [inline]
RIP: 0010:ipv6_frag_rcv+0x19c/0x2a20 net/ipv6/reassembly.c:328
Code: 5c 24 08 4c 89 74 24 10 48 8b 44 24 60 42 80 3c 28 00 74 08 48 89 df e8 42 15 21 f8 48 8b 03 49 89 c6 49 83 e6 fe 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 f7 e8 25 15 21 f8 bb 08 01 00 00 49 03
RSP: 0018:ffffc90003776d20 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88816d87a1d8 RCX: ffff88816bf65700
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90003776f08 R08: ffffea0006d29400 R09: 0000000b00007ff5
R10: ffffea0006d29400 R11: ffffffff8a04b090 R12: 0000000000000040
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff888173607480
FS: 00007fa70abdd6c0(0000) GS:ffff8882a9f2e000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000010000 CR3: 0000000112fa8000 CR4: 00000000000006f0
Call Trace:
<TASK>
nf_flow_ip6_tunnel_proto net/netfilter/nf_flow_table_ip.c:383 [inline]
nf_flow_skb_encap_protocol+0x9c2/0x1540 net/netfilter/nf_flow_table_ip.c:438
nf_flow_offload_ipv6_lookup net/netfilter/nf_flow_table_ip.c:1074 [inline]
nf_flow_offload_ipv6_hook+0x13c/0x32a0 net/netfilter/nf_flow_table_ip.c:1102
nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
nf_hook_slow+0xc5/0x220 net/netfilter/core.c:623
nf_hook_ingress include/linux/netfilter_netdev.h:34 [inline]
nf_ingress net/core/dev.c:5900 [inline]
__netif_receive_skb_core+0x241c/0x2f90 net/core/dev.c:5996
__netif_receive_skb_one_core net/core/dev.c:6135 [inline]
__netif_receive_skb+0x72/0x380 net/core/dev.c:6250
netif_receive_skb_internal net/core/dev.c:6336 [inline]
netif_receive_skb+0x1cb/0x790 net/core/dev.c:6395
tun_rx_batched+0x1b9/0x730 drivers/net/tun.c:1485
tun_get_user+0x2b65/0x3e90 drivers/net/tun.c:1953
tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1999
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c9/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa70b58f7c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa70abdd038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fa70b7e6090 RCX: 00007fa70b58f7c9
RDX: 000000000000fdef RSI: 0000200000000340 RDI: 0000000000000003
RBP: 00007fa70b5f297f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa70b7e6128 R14: 00007fa70b7e6090 R15: 00007ffcd9538b88
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:dst_dev include/net/dst.h:571 [inline]
RIP: 0010:skb_dst_dev include/net/dst.h:586 [inline]
RIP: 0010:skb_dst_dev_net include/net/dst.h:596 [inline]
RIP: 0010:ipv6_frag_rcv+0x19c/0x2a20 net/ipv6/reassembly.c:328
Code: 5c 24 08 4c 89 74 24 10 48 8b 44 24 60 42 80 3c 28 00 74 08 48 89 df e8 42 15 21 f8 48 8b 03 49 89 c6 49 83 e6 fe 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 f7 e8 25 15 21 f8 bb 08 01 00 00 49 03
RSP: 0018:ffffc90003776d20 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88816d87a1d8 RCX: ffff88816bf65700
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90003776f08 R08: ffffea0006d29400 R09: 0000000b00007ff5
R10: ffffea0006d29400 R11: ffffffff8a04b090 R12: 0000000000000040
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff888173607480
FS: 00007fa70abdd6c0(0000) GS:ffff8882a9f2e000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000010000 CR3: 0000000112fa8000 CR4: 00000000000006f0
----------------
Code disassembly (best guess):
0: 5c pop %rsp
1: 24 08 and $0x8,%al
3: 4c 89 74 24 10 mov %r14,0x10(%rsp)
8: 48 8b 44 24 60 mov 0x60(%rsp),%rax
d: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1)
12: 74 08 je 0x1c
14: 48 89 df mov %rbx,%rdi
17: e8 42 15 21 f8 call 0xf821155e
1c: 48 8b 03 mov (%rbx),%rax
1f: 49 89 c6 mov %rax,%r14
22: 49 83 e6 fe and $0xfffffffffffffffe,%r14
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 4c 89 f7 mov %r14,%rdi
34: e8 25 15 21 f8 call 0xf821155e
39: bb 08 01 00 00 mov $0x108,%ebx
3e: 49 rex.WB
3f: 03 .byte 0x3
***
general protection fault in nf_flow_offload_ipv6_hook
tree: nf-next
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/netfilter/nf-next.git
base: ff736a286116d462a4067ba258fa351bc0b4ed80
arch: amd64
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
config: https://ci.syzbot.org/builds/833219cc-e7e2-437d-b31c-1eb3666c1e93/config
C repro: https://ci.syzbot.org/findings/bee4a66a-8f79-4936-9f6e-7f9e229693c9/c_repro
syz repro: https://ci.syzbot.org/findings/bee4a66a-8f79-4936-9f6e-7f9e229693c9/syz_repro
Oops: general protection fault, probably for non-canonical address 0xdffffc000000000c: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000060-0x0000000000000067]
CPU: 1 UID: 0 PID: 5978 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:nf_flow_offload_ipv6_forward net/netfilter/nf_flow_table_ip.c:1027 [inline]
RIP: 0010:nf_flow_offload_ipv6_hook+0x2f3/0x32a0 net/netfilter/nf_flow_table_ip.c:1106
Code: 85 c6 03 00 00 e8 6d f0 31 f8 41 bc 14 00 00 00 e9 af 02 00 00 48 8d 4b 60 48 89 4c 24 18 48 c1 e9 03 48 89 8c 24 90 00 00 00 <42> 0f b6 04 21 84 c0 0f 85 de 23 00 00 44 0f b7 73 60 41 83 e6 03
RSP: 0018:ffffc900031d6fe0 EFLAGS: 00010206
RAX: ffffffff898e1101 RBX: 0000000000000002 RCX: 000000000000000c
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000000
RBP: ffffc900031d73e0 R08: ffffffff8f7d1e77 R09: 1ffffffff1efa3ce
R10: dffffc0000000000 R11: fffffbfff1efa3cf R12: dffffc0000000000
R13: 1ffff9200063ae1c R14: ffff88816cfc5680 R15: ffffc900031d72e0
FS: 00007fd7653a06c0(0000) GS:ffff8882a9f2e000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000010000 CR3: 000000011342a000 CR4: 00000000000006f0
Call Trace:
<TASK>
nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
nf_hook_slow+0xc5/0x220 net/netfilter/core.c:623
nf_hook_ingress include/linux/netfilter_netdev.h:34 [inline]
nf_ingress net/core/dev.c:5900 [inline]
__netif_receive_skb_core+0x241c/0x2f90 net/core/dev.c:5996
__netif_receive_skb_one_core net/core/dev.c:6135 [inline]
__netif_receive_skb+0x72/0x380 net/core/dev.c:6250
netif_receive_skb_internal net/core/dev.c:6336 [inline]
netif_receive_skb+0x1cb/0x790 net/core/dev.c:6395
tun_rx_batched+0x1b9/0x730 drivers/net/tun.c:1485
tun_get_user+0x2b65/0x3e90 drivers/net/tun.c:1953
tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1999
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c9/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd76458f7c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd7653a0038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fd7647e6090 RCX: 00007fd76458f7c9
RDX: 000000000000fdef RSI: 0000200000000380 RDI: 0000000000000003
RBP: 00007fd7645f297f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd7647e6128 R14: 00007fd7647e6090 R15: 00007ffde1f0b2b8
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:nf_flow_offload_ipv6_forward net/netfilter/nf_flow_table_ip.c:1027 [inline]
RIP: 0010:nf_flow_offload_ipv6_hook+0x2f3/0x32a0 net/netfilter/nf_flow_table_ip.c:1106
Code: 85 c6 03 00 00 e8 6d f0 31 f8 41 bc 14 00 00 00 e9 af 02 00 00 48 8d 4b 60 48 89 4c 24 18 48 c1 e9 03 48 89 8c 24 90 00 00 00 <42> 0f b6 04 21 84 c0 0f 85 de 23 00 00 44 0f b7 73 60 41 83 e6 03
RSP: 0018:ffffc900031d6fe0 EFLAGS: 00010206
RAX: ffffffff898e1101 RBX: 0000000000000002 RCX: 000000000000000c
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000000
RBP: ffffc900031d73e0 R08: ffffffff8f7d1e77 R09: 1ffffffff1efa3ce
R10: dffffc0000000000 R11: fffffbfff1efa3cf R12: dffffc0000000000
R13: 1ffff9200063ae1c R14: ffff88816cfc5680 R15: ffffc900031d72e0
FS: 00007fd7653a06c0(0000) GS:ffff8882a9f2e000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000010000 CR3: 000000011342a000 CR4: 00000000000006f0
----------------
Code disassembly (best guess):
0: 85 c6 test %eax,%esi
2: 03 00 add (%rax),%eax
4: 00 e8 add %ch,%al
6: 6d insl (%dx),%es:(%rdi)
7: f0 31 f8 lock xor %edi,%eax
a: 41 bc 14 00 00 00 mov $0x14,%r12d
10: e9 af 02 00 00 jmp 0x2c4
15: 48 8d 4b 60 lea 0x60(%rbx),%rcx
19: 48 89 4c 24 18 mov %rcx,0x18(%rsp)
1e: 48 c1 e9 03 shr $0x3,%rcx
22: 48 89 8c 24 90 00 00 mov %rcx,0x90(%rsp)
29: 00
* 2a: 42 0f b6 04 21 movzbl (%rcx,%r12,1),%eax <-- trapping instruction
2f: 84 c0 test %al,%al
31: 0f 85 de 23 00 00 jne 0x2415
37: 44 0f b7 73 60 movzwl 0x60(%rbx),%r14d
3c: 41 83 e6 03 and $0x3,%r14d
***
If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
Tested-by: syzbot@...kaller.appspotmail.com
---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@...glegroups.com.
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