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Message-ID: <692dd63e.a70a0220.d98e3.018c.GAE@google.com>
Date: Mon, 01 Dec 2025 09:54:06 -0800
From: syzbot ci <syzbot+ci42934faa3c3455b7@...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/20251201-flowtable-offload-ip6ip6-v1-0-1dabf534c074@kernel.org
* [PATCH RFC nf-next 1/4] netfilter: Introduce tunnel metadata info in nf_flowtable_ctx struct
* [PATCH RFC nf-next 2/4] netfilter: flowtable: Add IP6IP6 rx sw acceleration
* [PATCH RFC nf-next 3/4] netfilter: flowtable: Add IP6IP6 tx sw acceleration
* [PATCH RFC nf-next 4/4] selftests: netfilter: nft_flowtable.sh: Add IP6IP6 flowtable selftest
and found the following issue:
KASAN: slab-use-after-free Read in nf_flow_skb_encap_protocol
Full report is available here:
https://ci.syzbot.org/series/df395c22-6768-4a9f-9a96-56b5307acbc6
***
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/018f7259-7abc-4b77-b40c-e8e520e1e793/config
C repro: https://ci.syzbot.org/findings/5cb5bc43-721b-4a9e-a093-4d52aab5ba9f/c_repro
syz repro: https://ci.syzbot.org/findings/5cb5bc43-721b-4a9e-a093-4d52aab5ba9f/syz_repro
==================================================================
BUG: KASAN: slab-use-after-free in nf_flow_ip6_tunnel_proto net/netfilter/nf_flow_table_ip.c:383 [inline]
BUG: KASAN: slab-use-after-free in nf_flow_skb_encap_protocol+0x1336/0x14e0 net/netfilter/nf_flow_table_ip.c:433
Read of size 2 at addr ffff888115de92b6 by task syz.0.20/5970
CPU: 0 UID: 0 PID: 5970 Comm: syz.0.20 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:383 [inline]
nf_flow_skb_encap_protocol+0x1336/0x14e0 net/netfilter/nf_flow_table_ip.c:433
nf_flow_offload_ipv6_lookup net/netfilter/nf_flow_table_ip.c:1065 [inline]
nf_flow_offload_ipv6_hook+0x131/0x3380 net/netfilter/nf_flow_table_ip.c:1092
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: 0033:0x7f8b24f8f7c9
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:00007f8b25e26038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f8b251e6090 RCX: 00007f8b24f8f7c9
RDX: 000000000000fdef RSI: 0000200000000440 RDI: 0000000000000003
RBP: 00007f8b24ff297f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8b251e6128 R14: 00007f8b251e6090 R15: 00007ffe014b8a38
</TASK>
Allocated by task 5970:
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 5970:
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
icmpv6_param_prob include/linux/icmpv6.h:95 [inline]
ipv6_rthdr_rcv+0x150e/0x2020 net/ipv6/exthdrs.c:828
nf_flow_ip6_tunnel_proto net/netfilter/nf_flow_table_ip.c:381 [inline]
nf_flow_skb_encap_protocol+0x9b5/0x14e0 net/netfilter/nf_flow_table_ip.c:433
nf_flow_offload_ipv6_lookup net/netfilter/nf_flow_table_ip.c:1065 [inline]
nf_flow_offload_ipv6_hook+0x131/0x3380 net/netfilter/nf_flow_table_ip.c:1092
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 ffff888115de9200
which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 182 bytes inside of
freed 240-byte region [ffff888115de9200, ffff888115de92f0)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x115de8
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x17ff00000000040(head|node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 017ff00000000040 ffff8881036ba8c0 ffffea0004280a80 dead000000000002
raw: 0000000000000000 0000000080150015 00000000f5000000 0000000000000000
head: 017ff00000000040 ffff8881036ba8c0 ffffea0004280a80 dead000000000002
head: 0000000000000000 0000000080150015 00000000f5000000 0000000000000000
head: 017ff00000000001 ffffea0004577a01 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 5555, tgid 5555 (dhcpcd), ts 36767395595, free_ts 35122573404
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]
alloc_skb_with_frags+0xca/0x890 net/core/skbuff.c:6712
sock_alloc_send_pskb+0x84d/0x980 net/core/sock.c:2995
unix_dgram_sendmsg+0x454/0x1840 net/unix/af_unix.c:2139
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg+0x21c/0x270 net/socket.c:742
sock_write_iter+0x279/0x360 net/socket.c:1195
do_iter_readv_writev+0x623/0x8c0 fs/read_write.c:-1
vfs_writev+0x31a/0x960 fs/read_write.c:1057
page last free pid 5262 tgid 5262 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
getname_flags+0xb8/0x540 fs/namei.c:146
getname include/linux/fs.h:2924 [inline]
do_sys_openat2+0xbc/0x1c0 fs/open.c:1431
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1463
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
Memory state around the buggy address:
ffff888115de9180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888115de9200: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888115de9280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
^
ffff888115de9300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888115de9380: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
***
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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