general protection fault in ax25_send_frame

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    90cadbbf341d Merge git://git.kernel.org/pub/scm/linux/kern..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17127500c00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f9a32c9a4aef9af7
dashboard link: https://syzkaller.appspot.com/bug?extid=e0b81535a27b8be39502
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e0b81535a27b8be39502@xxxxxxxxxxxxxxxxxxxxxxxxx

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
kobject: 'loop3' (00000000a0e7275a): kobject_uevent_env
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 18625 Comm: blkid Not tainted 4.20.0-rc7+ #361
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:ax25_send_frame+0xe2/0x570 net/ax25/ax25_out.c:59
kobject: 'loop3' (00000000a0e7275a): fill_kobj_path: path  
= '/devices/virtual/block/loop3'
Code: 34 91 00 00 48 85 c0 0f 85 c2 03 00 00 e8 d6 bd 7e fa 48 8d bb 38 03  
00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 ea 03 00 00 48 8b 83 38 03 00 00 48 85 c0 48 89
RSP: 0018:ffff8880ae707518 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 1ffff1100a4e3951
RDX: 0000000000000067 RSI: ffffffff86ff9d4a RDI: 0000000000000338
RBP: ffff8880ae707558 R08: ffff88805271ca88 R09: 0000000000000002
R10: 0000000000000000 R11: ffff88805271c1c0 R12: ffff88809aec1a88
R13: ffffffff8be98280 R14: 0000000000000104 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
kobject: 'loop2' (0000000016318dbe): kobject_uevent_env
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff26e69ed8 CR3: 0000000097648000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 rose_send_frame+0xda/0x280 net/rose/rose_link.c:109
 rose_transmit_clear_request+0x1de/0x2a0 net/rose/rose_link.c:258
 rose_rx_call_request+0x4ea/0x1c90 net/rose/af_rose.c:999
 rose_loopback_timer+0x26a/0x3f0 net/rose/rose_loopback.c:100
 call_timer_fn+0x272/0x920 kernel/time/timer.c:1326
kobject: 'loop2' (0000000016318dbe): fill_kobj_path: path  
= '/devices/virtual/block/loop2'
 expire_timers kernel/time/timer.c:1363 [inline]
 __run_timers+0x7e5/0xc70 kernel/time/timer.c:1682
kobject: 'loop5' (00000000d24778f2): kobject_uevent_env
kobject: 'loop5' (00000000d24778f2): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
 run_timer_softirq+0x52/0xb0 kernel/time/timer.c:1695
 __do_softirq+0x30c/0xb2e kernel/softirq.c:292
kobject: 'loop3' (00000000a0e7275a): kobject_uevent_env
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0x17f/0x1c0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0x1cb/0x760 arch/x86/kernel/apic/apic.c:1061
kobject: 'loop3' (00000000a0e7275a): fill_kobj_path: path  
= '/devices/virtual/block/loop3'
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
 </IRQ>
RIP: 0010:write_comp_data+0x1/0x70 kernel/kcov.c:116
Code: e5 90 43 00 e9 a6 fc ff ff 4c 89 f7 e8 38 90 43 00 e9 6f fc ff ff e8  
9e b7 c9 ff 90 90 90 90 90 90 90 90 90 90 90 90 90 90 55 <48> 89 e5 65 4c  
8b 04 25 40 ee 01 00 65 8b 05 0c 93 83 7e a9 00 01
RSP: 0018:ffff888090d1f088 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
kobject: 'loop2' (0000000016318dbe): kobject_uevent_env
RAX: 0000000000000000 RBX: 00007f538b24f000 RCX: ffffffff81b177ab
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: ffff888090d1f098 R08: ffff88805271c1c0 R09: fffff94000052236
R10: fffff94000052236 R11: ffffea00002911b3 R12: 0000000000000025
R13: ffffea00002911c8 R14: dffffc0000000000 R15: ffffea00002911c0
kobject: 'loop2' (0000000016318dbe): fill_kobj_path: path  
= '/devices/virtual/block/loop2'
 zap_pte_range mm/memory.c:1082 [inline]
 zap_pmd_range mm/memory.c:1193 [inline]
 zap_pud_range mm/memory.c:1222 [inline]
 zap_p4d_range mm/memory.c:1243 [inline]
 unmap_page_range+0xc4b/0x25b0 mm/memory.c:1264
kobject: 'loop0' (00000000f27d2df2): kobject_uevent_env
kobject: 'loop0' (00000000f27d2df2): fill_kobj_path: path  
= '/devices/virtual/block/loop0'
 unmap_single_vma+0x19b/0x310 mm/memory.c:1309
 unmap_vmas+0x125/0x200 mm/memory.c:1339
 exit_mmap+0x2be/0x590 mm/mmap.c:3145
kobject: 'loop3' (00000000a0e7275a): kobject_uevent_env
 __mmput kernel/fork.c:1045 [inline]
 mmput+0x247/0x610 kernel/fork.c:1066
kobject: 'loop3' (00000000a0e7275a): fill_kobj_path: path  
= '/devices/virtual/block/loop3'
 exit_mm kernel/exit.c:545 [inline]
 do_exit+0xe74/0x26d0 kernel/exit.c:854
kobject: 'loop5' (00000000d24778f2): kobject_uevent_env
kobject: 'loop5' (00000000d24778f2): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
 do_group_exit+0x177/0x440 kernel/exit.c:970
 __do_sys_exit_group kernel/exit.c:981 [inline]
 __se_sys_exit_group kernel/exit.c:979 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:979
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f538b1e71e8
Code: Bad RIP value.
RSP: 002b:00007fff26e6cfa8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f538b1e71e8
RDX: 0000000000000002 RSI: 000000000000003c RDI: 0000000000000002
RBP: 00007f538b4bc840 R08: 00000000000000e7 R09: ffffffffffffffa8
R10: 00007f538b4c2740 R11: 0000000000000246 R12: 00007f538b4bc840
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 9b094a20ff9d7199 ]---
RIP: 0010:ax25_send_frame+0xe2/0x570 net/ax25/ax25_out.c:59
Code: 34 91 00 00 48 85 c0 0f 85 c2 03 00 00 e8 d6 bd 7e fa 48 8d bb 38 03  
00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 ea 03 00 00 48 8b 83 38 03 00 00 48 85 c0 48 89
RSP: 0018:ffff8880ae707518 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 1ffff1100a4e3951
RDX: 0000000000000067 RSI: ffffffff86ff9d4a RDI: 0000000000000338
RBP: ffff8880ae707558 R08: ffff88805271ca88 R09: 0000000000000002
R10: 0000000000000000 R11: ffff88805271c1c0 R12: ffff88809aec1a88
R13: ffffffff8be98280 R14: 0000000000000104 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f538b1e71be CR3: 0000000097648000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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