[syzbot] [netfilter?] general protection fault in nft_fib6_eval (2)

[syzbot <syzbot+109521837481c8e96ea5@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    01792bc3e5bd net: ti: icssg-prueth: Fix HSR and switch off..
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=108ec3bc580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c321f33e4545e2a1
dashboard link: https://syzkaller.appspot.com/bug?extid=109521837481c8e96ea5
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/deae9487bd6c/disk-01792bc3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1bb0140fd491/vmlinux-01792bc3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/bd9ec803c379/bzImage-01792bc3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+109521837481c8e96ea5@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 UID: 0 PID: 8151 Comm: syz.2.634 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:nft_fib6_eval+0x7cd/0xc20 net/ipv6/netfilter/nft_fib_ipv6.c:-1
Code: 4c 89 f3 48 81 c3 d8 00 00 00 48 89 d8 48 c1 e8 03 42 80 3c 20 00 74 08 48 89 df e8 8d df dd f7 48 8b 1b 48 89 d8 48 c1 e8 03 <42> 80 3c 20 00 74 08 48 89 df e8 74 df dd f7 48 8b 3b 48 8b 5c 24
RSP: 0018:ffffc9001c59f000 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000002
RDX: ffff88802fcabc00 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9001c59f1d0 R08: ffffffff8fa37e37 R09: 1ffffffff1f46fc6
R10: dffffc0000000000 R11: fffffbfff1f46fc7 R12: dffffc0000000000
R13: ffffc9001c59f0f0 R14: ffff88807f6db500 R15: ffff88807f6db560
FS:  00007faeb51596c0(0000) GS:ffff888125c1b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7baea82f98 CR3: 000000007e12a000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 expr_call_ops_eval net/netfilter/nf_tables_core.c:237 [inline]
 nft_do_chain+0x409/0x1920 net/netfilter/nf_tables_core.c:285
 nft_do_chain_inet+0x25d/0x340 net/netfilter/nft_chain_filter.c:161
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xc2/0x220 net/netfilter/core.c:623
 nf_hook include/linux/netfilter.h:273 [inline]
 NF_HOOK+0x206/0x3a0 include/linux/netfilter.h:316
 __netif_receive_skb_one_core net/core/dev.c:5991 [inline]
 __netif_receive_skb+0xd3/0x380 net/core/dev.c:6104
 netif_receive_skb_internal net/core/dev.c:6190 [inline]
 netif_receive_skb+0x1cb/0x790 net/core/dev.c:6249
 tun_rx_batched+0x1b9/0x730 drivers/net/tun.c:1485
 tun_get_user+0x2aa2/0x3e20 drivers/net/tun.c:1950
 tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
 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/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7faeb438d69f
Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 f9 92 02 00 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 48 89 44 24 08 e8 4c 93 02 00 48
RSP: 002b:00007faeb5159000 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007faeb45b5fa0 RCX: 00007faeb438d69f
RDX: 0000000000000046 RSI: 0000200000000b00 RDI: 00000000000000c8
RBP: 00007faeb4411e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000046 R11: 0000000000000293 R12: 0000000000000000
R13: 00007faeb45b6038 R14: 00007faeb45b5fa0 R15: 00007ffcdc4d36a8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:nft_fib6_eval+0x7cd/0xc20 net/ipv6/netfilter/nft_fib_ipv6.c:-1
Code: 4c 89 f3 48 81 c3 d8 00 00 00 48 89 d8 48 c1 e8 03 42 80 3c 20 00 74 08 48 89 df e8 8d df dd f7 48 8b 1b 48 89 d8 48 c1 e8 03 <42> 80 3c 20 00 74 08 48 89 df e8 74 df dd f7 48 8b 3b 48 8b 5c 24
RSP: 0018:ffffc9001c59f000 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000002
RDX: ffff88802fcabc00 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9001c59f1d0 R08: ffffffff8fa37e37 R09: 1ffffffff1f46fc6
R10: dffffc0000000000 R11: fffffbfff1f46fc7 R12: dffffc0000000000
R13: ffffc9001c59f0f0 R14: ffff88807f6db500 R15: ffff88807f6db560
FS:  00007faeb51596c0(0000) GS:ffff888125c1b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7baea82f98 CR3: 000000007e12a000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	4c 89 f3             	mov    %r14,%rbx
   3:	48 81 c3 d8 00 00 00 	add    $0xd8,%rbx
   a:	48 89 d8             	mov    %rbx,%rax
   d:	48 c1 e8 03          	shr    $0x3,%rax
  11:	42 80 3c 20 00       	cmpb   $0x0,(%rax,%r12,1)
  16:	74 08                	je     0x20
  18:	48 89 df             	mov    %rbx,%rdi
  1b:	e8 8d df dd f7       	call   0xf7dddfad
  20:	48 8b 1b             	mov    (%rbx),%rbx
  23:	48 89 d8             	mov    %rbx,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 80 3c 20 00       	cmpb   $0x0,(%rax,%r12,1) <-- trapping instruction
  2f:	74 08                	je     0x39
  31:	48 89 df             	mov    %rbx,%rdi
  34:	e8 74 df dd f7       	call   0xf7dddfad
  39:	48 8b 3b             	mov    (%rbx),%rdi
  3c:	48                   	rex.W
  3d:	8b                   	.byte 0x8b
  3e:	5c                   	pop    %rsp
  3f:	24                   	.byte 0x24


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