[syzbot] [kernel?] BUG: unable to handle kernel paging request in write_comp_data

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a2cf4ef33184 Merge tag 'devicetree-fixes-for-7.2' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16c0cc9e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f221a1b5d497ed15
dashboard link: https://syzkaller.appspot.com/bug?extid=237f670105a254a230d4
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6eb03d1a0722/disk-a2cf4ef3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4e0d90b14d28/vmlinux-a2cf4ef3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9b81b6ecaa65/bzImage-a2cf4ef3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+237f67...@syzkaller.appspotmail.com

BUG: unable to handle page fault for address: ffffc90013ccbfe8
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 13fe60067 P4D 13fe60067 PUD 1cafa067 PMD 61350067 PTE 0
Oops: Oops: 0002 [#1] SMP KASAN PTI
CPU: 0 UID: 0 PID: 19114 Comm: syz.3.1830 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:write_comp_data+0x75/0x90 kernel/kcov.c:267
Code: 00 8b bf fc 16 00 00 48 8b 30 48 c1 e7 03 4c 8d 1c b5 00 00 00 00 4a 8d 14 dd 28 00 00 00 48 39 d7 72 bd 48 83 c6 01 48 89 30 <4c> 89 44 10 e0 4c 89 4c 10 e8 4c 89 54 10 f0 4a 89 4c d8 20 c3 cc
RSP: 0018:ffffc90005a57e78 EFLAGS: 00050257
RAX: ffffc90013ccc000 RBX: 0000000000000000 RCX: ffffffff824589a5
RDX: 0000000000000008 RSI: 0000000000000000 RDI: 0000000000400000
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000002
R10: 0000000000000001 R11: fffffffffffffffc R12: 0000000000000020
R13: 0000000000000000 R14: 00007ffffffff000 R15: 0000000000000001
FS: 00007fa950b4b6c0(0000) GS:ffff888123de1000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffc90013ccbfe8 CR3: 000000005848c000 CR4: 00000000003526f0
Call Trace:
<TASK>
rseq_register+0x115/0x350 kernel/rseq.c:460
__do_sys_rseq kernel/rseq.c:561 [inline]
__se_sys_rseq kernel/rseq.c:547 [inline]
__x64_sys_rseq+0x1b8/0x2e0 kernel/rseq.c:547
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x840 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa95359e019
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:00007fa950b4b028 EFLAGS: 00000246 ORIG_RAX: 000000000000014e
RAX: ffffffffffffffda RBX: 00007fa953826450 RCX: 00007fa95359e019
RDX: 0000000000000000 RSI: 0000000000000020 RDI: 0000000000000000
RBP: 00007fa95363500c R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000000e R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa9538264e8 R14: 00007fa953826450 R15: 00007fff4d0e3998
</TASK>
Modules linked in:
CR2: ffffc90013ccbfe8
---[ end trace 0000000000000000 ]---
RIP: 0010:write_comp_data+0x75/0x90 kernel/kcov.c:267
Code: 00 8b bf fc 16 00 00 48 8b 30 48 c1 e7 03 4c 8d 1c b5 00 00 00 00 4a 8d 14 dd 28 00 00 00 48 39 d7 72 bd 48 83 c6 01 48 89 30 <4c> 89 44 10 e0 4c 89 4c 10 e8 4c 89 54 10 f0 4a 89 4c d8 20 c3 cc
RSP: 0018:ffffc90005a57e78 EFLAGS: 00050257
RAX: ffffc90013ccc000 RBX: 0000000000000000 RCX: ffffffff824589a5
RDX: 0000000000000008 RSI: 0000000000000000 RDI: 0000000000400000
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000002
R10: 0000000000000001 R11: fffffffffffffffc R12: 0000000000000020
R13: 0000000000000000 R14: 00007ffffffff000 R15: 0000000000000001
FS: 00007fa950b4b6c0(0000) GS:ffff888123de1000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffc90013ccbfe8 CR3: 000000005848c000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
0: 00 8b bf fc 16 00 add %cl,0x16fcbf(%rbx)
6: 00 48 8b add %cl,-0x75(%rax)
9: 30 48 c1 xor %cl,-0x3f(%rax)
c: e7 03 out %eax,$0x3
e: 4c 8d 1c b5 00 00 00 lea 0x0(,%rsi,4),%r11
15: 00
16: 4a 8d 14 dd 28 00 00 lea 0x28(,%r11,8),%rdx
1d: 00
1e: 48 39 d7 cmp %rdx,%rdi
21: 72 bd jb 0xffffffe0
23: 48 83 c6 01 add $0x1,%rsi
27: 48 89 30 mov %rsi,(%rax)
* 2a: 4c 89 44 10 e0 mov %r8,-0x20(%rax,%rdx,1) <-- trapping instruction
2f: 4c 89 4c 10 e8 mov %r9,-0x18(%rax,%rdx,1)
34: 4c 89 54 10 f0 mov %r10,-0x10(%rax,%rdx,1)
39: 4a 89 4c d8 20 mov %rcx,0x20(%rax,%r11,8)
3e: c3 ret
3f: cc int3


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