[moderation] [hams?] general protection fault in ax25_output

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: bf2e36c9dab9 dt-bindings: net: dsa: fix typos in bindings ..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=160d205a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=aeae47237b696a30
dashboard link: https://syzkaller.appspot.com/bug?extid=a33553d7dbe140fc9e3e
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [da...@davemloft.net edum...@google.com ho...@kernel.org jre...@yaina.de ku...@kernel.org linux...@vger.kernel.org linux-...@vger.kernel.org net...@vger.kernel.org pab...@redhat.com]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c23647e703c7/disk-bf2e36c9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/683229b23398/vmlinux-bf2e36c9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/502ea060b8a8/bzImage-bf2e36c9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a33553...@syzkaller.appspotmail.com

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: 17885 Comm: syz.3.11630 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/13/2026
RIP: 0010:ax25_output+0x899/0xa20 net/ax25/ax25_out.c:199
Code: 4b dd fe 49 8d 5f 28 48 89 d8 48 c1 e8 03 80 3c 28 00 74 08 48 89 df e8 d5 3a a8 f7 48 8b 1b 4c 8d 73 60 4c 89 f0 48 c1 e8 03 <0f> b6 04 28 84 c0 0f 85 e5 00 00 00 45 8b 36 4c 89 f7 48 c7 c6 90
RSP: 0018:ffffc900107df918 EFLAGS: 00010206
RAX: 000000000000000c RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000006 RSI: ffffffff8dccefc3 RDI: 00000000ffffffff
RBP: dffffc0000000000 R08: ffffffff8fef0f77 R09: 1ffffffff1fde1ee
R10: dffffc0000000000 R11: fffffbfff1fde1ef R12: ffff88805d53a6b0
R13: ffff88805d53a640 R14: 0000000000000060 R15: ffff8880739bc000
FS: 00007f2552a8e6c0(0000) GS:ffff8881257f3000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c30520d CR3: 0000000035342000 CR4: 00000000003526f0
Call Trace:
<TASK>
ax25_send_frame+0x310/0x9f0 net/ax25/ax25_out.c:-1
rose_send_frame net/rose/rose_link.c:106 [inline]
rose_transmit_restart_request net/rose/rose_link.c:198 [inline]
rose_transmit_link+0x729/0xac0 net/rose/rose_link.c:284
rose_write_internal+0x1256/0x1b60 net/rose/rose_subr.c:198
rose_connect+0x93b/0x1110 net/rose/af_rose.c:881
__sys_connect_file net/socket.c:2089 [inline]
__sys_connect+0x312/0x450 net/socket.c:2108
__do_sys_connect net/socket.c:2114 [inline]
__se_sys_connect net/socket.c:2111 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:2111
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2551b9aeb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2552a8e028 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007f2551e16090 RCX: 00007f2551b9aeb9
RDX: 0000000000000040 RSI: 0000200000000100 RDI: 000000000000000e
RBP: 00007f2551c08c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2551e16128 R14: 00007f2551e16090 R15: 00007ffd610ffd08
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ax25_output+0x899/0xa20 net/ax25/ax25_out.c:199
Code: 4b dd fe 49 8d 5f 28 48 89 d8 48 c1 e8 03 80 3c 28 00 74 08 48 89 df e8 d5 3a a8 f7 48 8b 1b 4c 8d 73 60 4c 89 f0 48 c1 e8 03 <0f> b6 04 28 84 c0 0f 85 e5 00 00 00 45 8b 36 4c 89 f7 48 c7 c6 90
RSP: 0018:ffffc900107df918 EFLAGS: 00010206
RAX: 000000000000000c RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000006 RSI: ffffffff8dccefc3 RDI: 00000000ffffffff
RBP: dffffc0000000000 R08: ffffffff8fef0f77 R09: 1ffffffff1fde1ee
R10: dffffc0000000000 R11: fffffbfff1fde1ef R12: ffff88805d53a6b0
R13: ffff88805d53a640 R14: 0000000000000060 R15: ffff8880739bc000
FS: 00007f2552a8e6c0(0000) GS:ffff8881256f3000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2551be8600 CR3: 0000000035342000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
0: 4b dd fe rex.WXB (bad)
3: 49 8d 5f 28 lea 0x28(%r15),%rbx
7: 48 89 d8 mov %rbx,%rax
a: 48 c1 e8 03 shr $0x3,%rax
e: 80 3c 28 00 cmpb $0x0,(%rax,%rbp,1)
12: 74 08 je 0x1c
14: 48 89 df mov %rbx,%rdi
17: e8 d5 3a a8 f7 call 0xf7a83af1
1c: 48 8b 1b mov (%rbx),%rbx
1f: 4c 8d 73 60 lea 0x60(%rbx),%r14
23: 4c 89 f0 mov %r14,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 0f b6 04 28 movzbl (%rax,%rbp,1),%eax <-- trapping instruction
2e: 84 c0 test %al,%al
30: 0f 85 e5 00 00 00 jne 0x11b
36: 45 8b 36 mov (%r14),%r14d
39: 4c 89 f7 mov %r14,%rdi
3c: 48 rex.W
3d: c7 .byte 0xc7
3e: c6 (bad)
3f: 90 nop


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