[Android 5.15] general protection fault in rtc_dev_ioctl

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dde14ee8fb2e Revert "of: property: add missing kerneldoc f..
git tree: android13-5.15-lts
console+strace: https://syzkaller.appspot.com/x/log.txt?x=13dab02d580000
kernel config: https://syzkaller.appspot.com/x/.config?x=98c60c31f9225e5e
dashboard link: https://syzkaller.appspot.com/bug?extid=adc43c7d3d8e60666e84
compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13688ea5580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11f87b0d580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d9ad4a61d93d/disk-dde14ee8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cb9cc7c9eae3/vmlinux-dde14ee8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/28d177f6b9a0/bzImage-dde14ee8.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+adc43c...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 PID: 304 Comm: syz-executor287 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
RIP: 0010:rtc_dev_ioctl+0x7b9/0x930 drivers/rtc/dev.c:387
Code: 85 f6 0f 84 d5 00 00 00 e8 a4 44 27 fe 48 c7 c0 f2 ff ff ff e9 b7 f9 ff ff e8 93 44 27 fe 4c 8b 74 24 38 4c 89 f0 48 c1 e8 03 <42> 80 3c 20 00 74 08 4c 89 f7 e8 f8 cc 66 fe 4d 8b 36 4d 85 f6 74
RSP: 0018:ffffc90000997d20 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88810bebb000 RCX: ffff88810ac60000
RDX: 0000000000000000 RSI: ffffffff86b9bcb0 RDI: 000000008004f50c
RBP: ffffc90000997e80 R08: ffff88810ac60000 R09: 000000000000000f
R10: 0000000080287010 R11: 0000000000000000 R12: dffffc0000000000
R13: 1ffff92000132fac R14: 0000000000000000 R15: dffffc0000000000
FS: 0000555592da43c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000062b5d8 CR3: 0000000121083000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0x121/0x1a0 fs/ioctl.c:860
__x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:860
x64_sys_call+0x2f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
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: 0033:0x7f22bdbbcd39
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 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 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcca83c368 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffcca83c498 RCX: 00007f22bdbbcd39
RDX: 0000000000000000 RSI: 000000008004f50c RDI: 0000000000000003
RBP: 0000000000000001 R08: 00007ffcca83c498 R09: 00007ffcca83c498
R10: 00007ffcca83c498 R11: 0000000000000246 R12: 00007ffcca83c488
R13: 0000000000000002 R14: 00007f22bdc4dca0 R15: 0000000000000002
</TASK>
Modules linked in:
---[ end trace 7df9818599d0a634 ]---
RIP: 0010:rtc_dev_ioctl+0x7b9/0x930 drivers/rtc/dev.c:387
Code: 85 f6 0f 84 d5 00 00 00 e8 a4 44 27 fe 48 c7 c0 f2 ff ff ff e9 b7 f9 ff ff e8 93 44 27 fe 4c 8b 74 24 38 4c 89 f0 48 c1 e8 03 <42> 80 3c 20 00 74 08 4c 89 f7 e8 f8 cc 66 fe 4d 8b 36 4d 85 f6 74
RSP: 0018:ffffc90000997d20 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88810bebb000 RCX: ffff88810ac60000
RDX: 0000000000000000 RSI: ffffffff86b9bcb0 RDI: 000000008004f50c
RBP: ffffc90000997e80 R08: ffff88810ac60000 R09: 000000000000000f
R10: 0000000080287010 R11: 0000000000000000 R12: dffffc0000000000
R13: 1ffff92000132fac R14: 0000000000000000 R15: dffffc0000000000
FS: 0000555592da43c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000062b5d8 CR3: 0000000121083000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 85 f6 test %esi,%esi
2: 0f 84 d5 00 00 00 je 0xdd
8: e8 a4 44 27 fe call 0xfe2744b1
d: 48 c7 c0 f2 ff ff ff mov $0xfffffffffffffff2,%rax
14: e9 b7 f9 ff ff jmp 0xfffff9d0
19: e8 93 44 27 fe call 0xfe2744b1
1e: 4c 8b 74 24 38 mov 0x38(%rsp),%r14
23: 4c 89 f0 mov %r14,%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: 4c 89 f7 mov %r14,%rdi
34: e8 f8 cc 66 fe call 0xfe66cd31
39: 4d 8b 36 mov (%r14),%r14
3c: 4d 85 f6 test %r14,%r14
3f: 74 .byte 0x74


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup