[syzbot] [reiserfs?] general protection fault in account_system_index_time (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 715abedee4cd Add linux-next specific files for 20230515
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12ec7b85280000
kernel config: https://syzkaller.appspot.com/x/.config?x=6a2745d066dda0ec
dashboard link: https://syzkaller.appspot.com/bug?extid=5444b0cc48f4e1939d72
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17956736280000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=175da599280000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d4d1d06b34b8/disk-715abede.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3ef33a86fdc8/vmlinux-715abede.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e0006b413ed1/bzImage-715abede.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/525b69f4318a/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5444b0...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0040000033: 0000 [#1] PREEMPT SMP KASAN
KASAN: probably user-memory-access in range [0x0000000200000198-0x000000020000019f]
CPU: 1 PID: 262216 Comm: Not tainted 6.4.0-rc2-next-20230515-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/25/2023
RIP: 0010:get_running_cputimer include/linux/sched/cputime.h:79 [inline]
RIP: 0010:account_group_system_time include/linux/sched/cputime.h:143 [inline]
RIP: 0010:account_system_index_time+0x86/0x2f0 kernel/sched/cputime.c:173
Code: 63 02 00 00 48 8b 9d f8 08 00 00 48 b8 00 00 00 00 00 fc ff df 48 8d bb 98 01 00 00 4c 8d b3 38 01 00 00 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e e7 01 00 00 8b 83 98 01 00 00
RSP: 0018:ffffc900001e0da0 EFLAGS: 00010006
RAX: dffffc0000000000 RBX: 0000000200000001 RCX: 1ffffffff1827d41
RDX: 0000000040000033 RSI: 000000000097fff6 RDI: 0000000200000199
RBP: ffff88807638bb80 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffffffffffff R12: 000000000097fff6
R13: 0000000000000002 R14: 0000000200000139 R15: ffffffff817770e0
FS: 00005555556c1300(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffca0efd000 CR3: 0000000019395000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
update_process_times+0x26/0x1a0 kernel/time/timer.c:2069
tick_sched_handle+0x8e/0x170 kernel/time/tick-sched.c:243
tick_sched_timer+0xee/0x110 kernel/time/tick-sched.c:1481
__run_hrtimer kernel/time/hrtimer.c:1685 [inline]
__hrtimer_run_queues+0x1c0/0xa30 kernel/time/hrtimer.c:1749
hrtimer_interrupt+0x320/0x7b0 kernel/time/hrtimer.c:1811
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1095 [inline]
__sysvec_apic_timer_interrupt+0x14a/0x430 arch/x86/kernel/apic/apic.c:1112
sysvec_apic_timer_interrupt+0x92/0xc0 arch/x86/kernel/apic/apic.c:1106
</IRQ>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:get_running_cputimer include/linux/sched/cputime.h:79 [inline]
RIP: 0010:account_group_system_time include/linux/sched/cputime.h:143 [inline]
RIP: 0010:account_system_index_time+0x86/0x2f0 kernel/sched/cputime.c:173
Code: 63 02 00 00 48 8b 9d f8 08 00 00 48 b8 00 00 00 00 00 fc ff df 48 8d bb 98 01 00 00 4c 8d b3 38 01 00 00 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e e7 01 00 00 8b 83 98 01 00 00
RSP: 0018:ffffc900001e0da0 EFLAGS: 00010006
RAX: dffffc0000000000 RBX: 0000000200000001 RCX: 1ffffffff1827d41
RDX: 0000000040000033 RSI: 000000000097fff6 RDI: 0000000200000199
RBP: ffff88807638bb80 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffffffffffff R12: 000000000097fff6
R13: 0000000000000002 R14: 0000000200000139 R15: ffffffff817770e0
FS: 00005555556c1300(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffca0efd000 CR3: 0000000019395000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 63 02 movsxd (%rdx),%eax
2: 00 00 add %al,(%rax)
4: 48 8b 9d f8 08 00 00 mov 0x8f8(%rbp),%rbx
b: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
12: fc ff df
15: 48 8d bb 98 01 00 00 lea 0x198(%rbx),%rdi
1c: 4c 8d b3 38 01 00 00 lea 0x138(%rbx),%r14
23: 48 89 fa mov %rdi,%rdx
26: 48 c1 ea 03 shr $0x3,%rdx
* 2a: 0f b6 04 02 movzbl (%rdx,%rax,1),%eax <-- trapping instruction
2e: 84 c0 test %al,%al
30: 74 08 je 0x3a
32: 3c 03 cmp $0x3,%al
34: 0f 8e e7 01 00 00 jle 0x221
3a: 8b 83 98 01 00 00 mov 0x198(%rbx),%eax


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[Thomas Gleixner]

> Code disassembly (best guess):

I built with that config and stared at the disassembly.

RBP contains the task pointer, which looks valid RBP: ffff88807638bb80

> 4: 48 8b 9d f8 08 00 00 mov 0x8f8(%rbp),%rbx

struct signal_struct * signal; /* 2296 8 */

2296 == 0x8f8

So this loads tsk->signal into RBX

RBX: 0000000200000001

which is clearly not a valid signal_struct pointer...

The rest is a consequence of this.

> b: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
> 12: fc ff df
> 15: 48 8d bb 98 01 00 00 lea 0x198(%rbx),%rdi
> 1c: 4c 8d b3 38 01 00 00 lea 0x138(%rbx),%r14
> 23: 48 89 fa mov %rdi,%rdx
> 26: 48 c1 ea 03 shr $0x3,%rdx
> * 2a: 0f b6 04 02 movzbl (%rdx,%rax,1),%eax <-- trapping instruction
> 2e: 84 c0 test %al,%al
> 30: 74 08 je 0x3a
> 32: 3c 03 cmp $0x3,%al
> 34: 0f 8e e7 01 00 00 jle 0x221
> 3a: 8b 83 98 01 00 00 mov 0x198(%rbx),%eax

Looks like good old memory corruption. tsk->comm looks weird too:

> CPU: 1 PID: 262216 Comm: Not tainted 6.4.0-rc2-next-20230515-syzkaller #0

tsk>comm is at offset 0x898 so close enough to the corrupted
tsk->signal.

I let the reiserfs wizards decode the root cause :)

Thanks,

tglx

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.