[syzbot] [net?] WARNING in ah6_output

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9e89db3d847f Merge tag 'linux-can-fixes-for-6.15-20250520'..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=1476d1f4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c3f0e807ec5d1268
dashboard link: https://syzkaller.appspot.com/bug?extid=01b0667934cdceb4451c
compiler: Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8b09322b598e/disk-9e89db3d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/23ed08e707b5/vmlinux-9e89db3d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/be78b62450e7/bzImage-9e89db3d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+01b066...@syzkaller.appspotmail.com

------------[ cut here ]------------
memcpy: detected field-spanning write (size 40) of single field "&top_iph->saddr" at net/ipv6/ah6.c:439 (size 16)
WARNING: CPU: 0 PID: 8838 at net/ipv6/ah6.c:439 ah6_output+0xe7e/0x14e0 net/ipv6/ah6.c:439
Modules linked in:
CPU: 0 UID: 0 PID: 8838 Comm: syz.1.814 Not tainted 6.15.0-rc6-syzkaller-00173-g9e89db3d847f #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:ah6_output+0xe7e/0x14e0 net/ipv6/ah6.c:439
Code: ff e8 36 80 9f f7 c6 05 bb 97 48 05 01 90 b9 10 00 00 00 48 c7 c7 a0 56 7e 8c 4c 89 fe 48 c7 c2 00 59 7e 8c e8 a3 dc 63 f7 90 <0f> 0b 90 90 e9 b5 fe ff ff e8 74 e4 35 01 48 8b 4c 24 10 80 e1 07
RSP: 0018:ffffc900049f70e0 EFLAGS: 00010246
RAX: 3fffcb5d3bcc7c00 RBX: 0000000000000028 RCX: 0000000000080000
RDX: ffffc9000ece1000 RSI: 00000000000052e8 RDI: 00000000000052e9
RBP: ffffc900049f7250 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff1bba944 R12: dffffc0000000000
R13: 1ffff9200093ee38 R14: ffff8881452e8800 R15: 0000000000000028
FS: 00007fc3a1d2c6c0(0000) GS:ffff8881260c7000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555569628808 CR3: 000000005cf4e000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
xfrm_output_one net/xfrm/xfrm_output.c:555 [inline]
xfrm_output_resume+0x2c55/0x6170 net/xfrm/xfrm_output.c:590
__xfrm6_output+0x2eb/0x1070 net/ipv6/xfrm6_output.c:103
NF_HOOK_COND include/linux/netfilter.h:303 [inline]
xfrm6_output+0x1c6/0x4f0 net/ipv6/xfrm6_output.c:108
ip6_send_skb+0x1d5/0x390 net/ipv6/ip6_output.c:1981
l2tp_ip6_sendmsg+0x1378/0x1870 net/l2tp/l2tp_ip6.c:661
sock_sendmsg_nosec net/socket.c:712 [inline]
__sock_sendmsg+0x19c/0x270 net/socket.c:727
____sys_sendmsg+0x505/0x830 net/socket.c:2566
___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620
__sys_sendmsg net/socket.c:2652 [inline]
__do_sys_sendmsg net/socket.c:2657 [inline]
__se_sys_sendmsg net/socket.c:2655 [inline]
__x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc3a0f8e969
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:00007fc3a1d2c038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fc3a11b6080 RCX: 00007fc3a0f8e969
RDX: 0000000000000800 RSI: 0000200000000540 RDI: 0000000000000004
RBP: 00007fc3a1010ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fc3a11b6080 R15: 00007ffc18a80a58
</TASK>


---
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#syz undup

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 9caca6ac0e26 bnxt: properly flush XDP redirect lists
git tree: net
console+strace: https://syzkaller.appspot.com/x/log.txt?x=16254f0c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d11f52d3049c3790
dashboard link: https://syzkaller.appspot.com/bug?extid=01b0667934cdceb4451c
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1252bdd4580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1715d182580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b5b575608bd0/disk-9caca6ac.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5c5f5f06115c/vmlinux-9caca6ac.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d833e4fd921e/bzImage-9caca6ac.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+01b066...@syzkaller.appspotmail.com

------------[ cut here ]------------
memcpy: detected field-spanning write (size 40) of single field "&top_iph->saddr" at net/ipv6/ah6.c:439 (size 16)

WARNING: CPU: 0 PID: 5841 at net/ipv6/ah6.c:439 ah6_output+0xece/0x1510 net/ipv6/ah6.c:439
Modules linked in:
CPU: 0 UID: 0 PID: 5841 Comm: syz-executor125 Not tainted 6.16.0-rc2-syzkaller-00179-g9caca6ac0e26 #0 PREEMPT(full)

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025

RIP: 0010:ah6_output+0xece/0x1510 net/ipv6/ah6.c:439
Code: ff e8 e6 09 91 f7 c6 05 d6 c0 5b 05 01 90 b9 10 00 00 00 48 c7 c7 60 64 a0 8c 4c 89 f6 48 c7 c2 c0 66 a0 8c e8 73 b4 54 f7 90 <0f> 0b 90 90 e9 ab fe ff ff e8 c4 14 37 01 48 8b 4c 24 28 80 e1 07
RSP: 0018:ffffc900041a70a0 EFLAGS: 00010246
RAX: 6316bcc3c9618000 RBX: ffff888030ed5808 RCX: ffff888079c1da00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: ffffc900041a7230 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff1bfa9ec R12: dffffc0000000000
R13: 1ffff92000834e34 R14: 0000000000000028 R15: 0000000000000030
FS: 000055556d6c9380(0000) GS:ffff888125c51000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007fe027d09e9c CR3: 0000000074d90000 CR4: 00000000003526f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
xfrm_output_one net/xfrm/xfrm_output.c:555 [inline]
xfrm_output_resume+0x2c55/0x6170 net/xfrm/xfrm_output.c:590
__xfrm6_output+0x2eb/0x1070 net/ipv6/xfrm6_output.c:103

NF_HOOK_COND include/linux/netfilter.h:306 [inline]
xfrm6_output+0x1c6/0x4f0 net/ipv6/xfrm6_output.c:108
ip6_send_skb+0x1d5/0x390 net/ipv6/ip6_output.c:1982
l2tp_ip6_sendmsg+0x12ee/0x17c0 net/l2tp/l2tp_ip6.c:661

sock_sendmsg_nosec net/socket.c:712 [inline]
__sock_sendmsg+0x19c/0x270 net/socket.c:727
____sys_sendmsg+0x505/0x830 net/socket.c:2566
___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620
__sys_sendmsg net/socket.c:2652 [inline]
__do_sys_sendmsg net/socket.c:2657 [inline]
__se_sys_sendmsg net/socket.c:2655 [inline]
__x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]

do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1b7b30bc79
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdde4e6fd8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f1b7b30bc79
RDX: 0000000000000800 RSI: 0000200000000540 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000006 R09: 0000000000000006

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000001
</TASK>


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

[Charalampos Mitrodimas]

syzbot <syzbot+01b066...@syzkaller.appspotmail.com> writes:

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 9e89db3d847f Merge tag 'linux-can-fixes-for-6.15-20250520'..
> git tree: net
> console output: https://syzkaller.appspot.com/x/log.txt?x=1476d1f4580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=c3f0e807ec5d1268
> dashboard link: https://syzkaller.appspot.com/bug?extid=01b0667934cdceb4451c
> compiler: Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/8b09322b598e/disk-9e89db3d.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/23ed08e707b5/vmlinux-9e89db3d.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/be78b62450e7/bzImage-9e89db3d.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+01b066...@syzkaller.appspotmail.com
>
> ------------[ cut here ]------------
> memcpy: detected field-spanning write (size 40) of single field "&top_iph->saddr" at net/ipv6/ah6.c:439 (size 16)

This could be happening because

memcpy(&top_iph->saddr, iph_ext, extlen)

tries to copy extension headers (40 bytes) into the IPv6 saddr field (16
bytes), when extension headers should be at

(u8*)top_iph + sizeof(*top_iph)

if I'm not mistaken.

C. Mitrodimas

[Charalampos Mitrodimas]

#syz test: https://github.com/charmitro/linux.git d4017cef5514575221234e65a2ff9b0713718274

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+01b066...@syzkaller.appspotmail.com
Tested-by: syzbot+01b066...@syzkaller.appspotmail.com

Tested on:

commit: d4017cef net: ipv6: fix buffer overflow in AH output
git tree: https://github.com/charmitro/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1560a782580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d80adbc1e1d0bde4
dashboard link: https://syzkaller.appspot.com/bug?extid=01b0667934cdceb4451c
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.