general protection fault in fou_nl_add_doit

general protection fault in fou_nl_add_doit

[sanan.hasanou]

Good day, dear maintainers,

We found a bug using a modified version of syzkaller.

Kernel Branch: 7.0-rc1
Kernel Config: <https://drive.google.com/open?id=1RsqMUgdFUMq9-iREK8DZCvDfjq0RWm5X>
Reproducer: <https://drive.google.com/open?id=1KNnULJOSBve4YaFQT2Z-pK2Ms8LwRN7P>
Thank you!

Best regards,
Sanan Hasanov

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
CPU: 0 UID: 0 PID: 326872 Comm: syz.6.71753 Tainted: G             L      7.0.0-rc1 #1 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:fou_create net/ipv4/fou_core.c:590 [inline]
RIP: 0010:fou_nl_add_doit+0x236/0xaa0 net/ipv4/fou_core.c:764
Code: 48 89 da 4d 89 2c 24 48 85 d2 0f 84 eb 07 00 00 4c 8b 6c 24 60 49 8d 5d 18 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 48 89 54 24 10 74 0d 48 89 df e8 47 c2 90 f8 48 8b 54
RSP: 0018:ffffc9002b54f260 EFLAGS: 00010216
RAX: 0000000000000003 RBX: 0000000000000018 RCX: dffffc0000000000
RDX: ffff88801aeb8d00 RSI: 00000000000002d1 RDI: 00000000ffffffff
RBP: ffffc9002b54f3d0 R08: ffffffff8ef0f1bf R09: 1ffffffff1de1e37
R10: dffffc0000000000 R11: fffffbfff1de1e38 R12: ffff88801d9a3a38
R13: 0000000000000000 R14: ffff88802440dd00 R15: ffffc9002b54f440
FS:  00007f863f9266c0(0000) GS:ffff88809d305000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c40b6a1 CR3: 0000000026d9b000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 genl_family_rcv_msg_doit+0x20d/0x2f0 net/netlink/genetlink.c:1114
 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
 genl_rcv_msg+0x60c/0x790 net/netlink/genetlink.c:1209
 netlink_rcv_skb+0x206/0x460 net/netlink/af_netlink.c:2550
 genl_rcv+0x31/0x40 net/netlink/genetlink.c:1218
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0xa42/0xc00 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x7ed/0xb00 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0x4dd/0x8e0 net/socket.c:2592
 ___sys_sendmsg+0x1ee/0x260 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x189/0x240 net/socket.c:2681
 x64_sys_call+0x17a2/0x2900 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x110/0x8a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x7f86416d3b6d
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f863f926018 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f8641945fa0 RCX: 00007f86416d3b6d
RDX: 0000000000000000 RSI: 0000200000000280 RDI: 0000000000000003
RBP: 00007f8641777c3e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8641946038 R14: 00007f8641945fa0 R15: 00007ffce4a75000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:fou_create net/ipv4/fou_core.c:590 [inline]
RIP: 0010:fou_nl_add_doit+0x236/0xaa0 net/ipv4/fou_core.c:764
Code: 48 89 da 4d 89 2c 24 48 85 d2 0f 84 eb 07 00 00 4c 8b 6c 24 60 49 8d 5d 18 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 48 89 54 24 10 74 0d 48 89 df e8 47 c2 90 f8 48 8b 54
RSP: 0018:ffffc9002b54f260 EFLAGS: 00010216
RAX: 0000000000000003 RBX: 0000000000000018 RCX: dffffc0000000000
RDX: ffff88801aeb8d00 RSI: 00000000000002d1 RDI: 00000000ffffffff
RBP: ffffc9002b54f3d0 R08: ffffffff8ef0f1bf R09: 1ffffffff1de1e37
R10: dffffc0000000000 R11: fffffbfff1de1e38 R12: ffff88801d9a3a38
R13: 0000000000000000 R14: ffff88802440dd00 R15: ffffc9002b54f440
FS:  00007f863f9266c0(0000) GS:ffff88809d305000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc1ad9e3080 CR3: 0000000026d9b000 CR4: 00000000000006f0
----------------
Code disassembly (best guess):
   0:	48 89 da             	mov    %rbx,%rdx
   3:	4d 89 2c 24          	mov    %r13,(%r12)
   7:	48 85 d2             	test   %rdx,%rdx
   a:	0f 84 eb 07 00 00    	je     0x7fb
  10:	4c 8b 6c 24 60       	mov    0x60(%rsp),%r13
  15:	49 8d 5d 18          	lea    0x18(%r13),%rbx
  19:	48 89 d8             	mov    %rbx,%rax
  1c:	48 c1 e8 03          	shr    $0x3,%rax
  20:	48 b9 00 00 00 00 00 	movabs $0xdffffc0000000000,%rcx
  27:	fc ff df
* 2a:	80 3c 08 00          	cmpb   $0x0,(%rax,%rcx,1) <-- trapping instruction
  2e:	48 89 54 24 10       	mov    %rdx,0x10(%rsp)
  33:	74 0d                	je     0x42
  35:	48 89 df             	mov    %rbx,%rdi
  38:	e8 47 c2 90 f8       	call   0xf890c284
  3d:	48                   	rex.W
  3e:	8b                   	.byte 0x8b
  3f:	54                   	push   %rsp

<<<<<<<<<<<<<<< tail report >>>>>>>>>>>>>>>

Re: general protection fault in fou_nl_add_doit

[Jakub Kicinski]

On Thu, 18 Jun 2026 15:22:28 -0700 (PDT) sanan.hasanou@gmail.com wrote:
> We found a bug using a modified version of syzkaller.
> 
> Kernel Branch: 7.0-rc1

That's an old kernel. Did you re-run this on 7.1?