syzbot


general protection fault in ax25_send_control

Status: upstream: reported on 2026/02/25 03:52
Reported-by: syzbot+fc560ce39424d5e16dbe@syzkaller.appspotmail.com
First crash: 3d21h, last: 3d21h
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream general protection fault in ax25_send_control hams 2 1 2609d 2608d 0/29 auto-closed as invalid on 2019/07/06 21:28
linux-5.15 KASAN: use-after-free Read in ax25_send_control 19 1 344d 344d 0/3 auto-obsoleted due to no activity on 2025/06/29 16:19

Sample crash report:
general protection fault, probably for non-canonical address 0xdffffc000000001a: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000000d0-0x00000000000000d7]
CPU: 0 PID: 9028 Comm: syz.4.1026 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:ax25_send_control+0x78/0x4e0 net/ax25/ax25_subr.c:152
Code: 48 83 c3 08 48 89 d8 48 c1 e8 03 42 80 3c 30 00 74 08 48 89 df e8 88 67 ea f8 41 bf d6 00 00 00 4c 03 3b 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 30 84 c0 0f 85 03 03 00 00 41 0f b7 3f 83 c7 02 be 20
RSP: 0018:ffffc9000320f9f0 EFLAGS: 00010203
RAX: 000000000000001a RBX: ffff888026b2d008 RCX: 0000000000080000
RDX: ffffc90004004000 RSI: 000000000000389e RDI: 000000000000389f
RBP: 000000000000002f R08: ffff888017abbb80 R09: 0000000000000003
R10: 0000000000000002 R11: 0000000000000002 R12: ffff88805b31e828
R13: 1ffff1100b663d05 R14: dffffc0000000000 R15: 00000000000000d6
FS:  00007faad38f16c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b34f17ff8 CR3: 0000000048596000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 ax25_std_establish_data_link+0x97/0x110 net/ax25/ax25_std_subr.c:-1
 ax25_send_frame+0x313/0x490 net/ax25/ax25_out.c:78
 rose_send_frame+0x111/0x220 net/rose/rose_link.c:106
 rose_transmit_restart_request net/rose/rose_link.c:198 [inline]
 rose_transmit_link+0x463/0x730 net/rose/rose_link.c:284
 rose_write_internal+0x680/0x1e90 net/rose/rose_subr.c:198
 rose_connect+0xada/0x13b0 net/rose/af_rose.c:875
 __sys_connect_file net/socket.c:1932 [inline]
 __sys_connect+0x3cb/0x450 net/socket.c:1949
 __do_sys_connect net/socket.c:1959 [inline]
 __se_sys_connect net/socket.c:1956 [inline]
 __x64_sys_connect+0x76/0x80 net/socket.c:1956
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7faad5697629
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:00007faad38f1028 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007faad5910fa0 RCX: 00007faad5697629
RDX: 000000000000001c RSI: 0000200000000240 RDI: 0000000000000009
RBP: 00007faad572db39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007faad5911038 R14: 00007faad5910fa0 R15: 00007ffee3246448
 </TASK>
Modules linked in:
---[ end trace 3de9a202cad3efec ]---
RIP: 0010:ax25_send_control+0x78/0x4e0 net/ax25/ax25_subr.c:152
Code: 48 83 c3 08 48 89 d8 48 c1 e8 03 42 80 3c 30 00 74 08 48 89 df e8 88 67 ea f8 41 bf d6 00 00 00 4c 03 3b 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 30 84 c0 0f 85 03 03 00 00 41 0f b7 3f 83 c7 02 be 20
RSP: 0018:ffffc9000320f9f0 EFLAGS: 00010203
RAX: 000000000000001a RBX: ffff888026b2d008 RCX: 0000000000080000
RDX: ffffc90004004000 RSI: 000000000000389e RDI: 000000000000389f
RBP: 000000000000002f R08: ffff888017abbb80 R09: 0000000000000003
R10: 0000000000000002 R11: 0000000000000002 R12: ffff88805b31e828
R13: 1ffff1100b663d05 R14: dffffc0000000000 R15: 00000000000000d6
FS:  00007faad38f16c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4f945f72f8 CR3: 0000000048596000 CR4: 00000000003506f0
----------------
Code disassembly (best guess):
   0:	48 83 c3 08          	add    $0x8,%rbx
   4:	48 89 d8             	mov    %rbx,%rax
   7:	48 c1 e8 03          	shr    $0x3,%rax
   b:	42 80 3c 30 00       	cmpb   $0x0,(%rax,%r14,1)
  10:	74 08                	je     0x1a
  12:	48 89 df             	mov    %rbx,%rdi
  15:	e8 88 67 ea f8       	call   0xf8ea67a2
  1a:	41 bf d6 00 00 00    	mov    $0xd6,%r15d
  20:	4c 03 3b             	add    (%rbx),%r15
  23:	4c 89 f8             	mov    %r15,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 0f b6 04 30       	movzbl (%rax,%r14,1),%eax <-- trapping instruction
  2f:	84 c0                	test   %al,%al
  31:	0f 85 03 03 00 00    	jne    0x33a
  37:	41 0f b7 3f          	movzwl (%r15),%edi
  3b:	83 c7 02             	add    $0x2,%edi
  3e:	be                   	.byte 0xbe
  3f:	20                   	.byte 0x20

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/25 03:51 linux-5.15.y 3330a8d33e08 787dfb7c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan general protection fault in ax25_send_control
* Struck through repros no longer work on HEAD.