linux-kernel - Re: [syzbot] UBSAN: shift-out-of-bounds in detach

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Message-ID: <000000000000b3462405bf34ebb7@google.com>
Date:   Mon, 05 Apr 2021 00:48:17 -0700
From:   syzbot <syzbot+f9131489729201445f66@...kaller.appspotmail.com>
To:     akpm@...ux-foundation.org, bp@...en8.de, dwmw@...zon.co.uk,
        hpa@...or.com, linux-kernel@...r.kernel.org, luto@...nel.org,
        mingo@...hat.com, syzkaller-bugs@...glegroups.com,
        tglx@...utronix.de, x86@...nel.org
Subject: Re: [syzbot] UBSAN: shift-out-of-bounds in detach_tasks

syzbot has found a reproducer for the following issue on:

HEAD commit:    e49d033b Linux 5.12-rc6
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15f7cc6ad00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f91155ccddaf919c
dashboard link: https://syzkaller.appspot.com/bug?extid=f9131489729201445f66
compiler:       Debian clang version 11.0.1-2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13dc5786d00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f9131489729201445f66@...kaller.appspotmail.com

================================================================================
UBSAN: shift-out-of-bounds in kernel/sched/fair.c:7712:14
shift exponent 77 is too large for 64-bit type 'unsigned long'
CPU: 1 PID: 8407 Comm: syz-executor.4 Not tainted 5.12.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x176/0x24e lib/dump_stack.c:120
 ubsan_epilogue lib/ubsan.c:148 [inline]
 __ubsan_handle_shift_out_of_bounds+0x42e/0x4d0 lib/ubsan.c:327
 detach_tasks+0xd04/0x1110 kernel/sched/fair.c:7712
 load_balance+0x39f6/0x5a80 kernel/sched/fair.c:9641
 rebalance_domains+0x4ca/0x9c0 kernel/sched/fair.c:10029
 __do_softirq+0x318/0x714 kernel/softirq.c:345
 invoke_softirq kernel/softirq.c:221 [inline]
 __irq_exit_rcu+0x1d8/0x200 kernel/softirq.c:422
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:434
 sysvec_apic_timer_interrupt+0x91/0xb0 arch/x86/kernel/apic/apic.c:1100
 </IRQ>
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:169 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x25/0x40 kernel/locking/spinlock.c:199
Code: b2 fd ff 66 90 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 0e 54 08 f8 48 89 df e8 56 29 0a f8 e8 f1 a4 2a f8 fb bf 01 00 00 00 <e8> 26 39 fe f7 65 8b 05 f7 7c ad 76 85 c0 74 02 5b c3 e8 ab d8 ab
RSP: 0018:ffffc9000187fc70 EFLAGS: 00000282
RAX: eded0b76c3f98d00 RBX: ffff8880b9d34c80 RCX: ffffffff8ff89b03
RDX: 0000000040000000 RSI: 0000000000000002 RDI: 0000000000000001
RBP: ffffc9000187fcd0 R08: ffffffff817f17a0 R09: ffffed10173a6991
R10: ffffed10173a6991 R11: 0000000000000000 R12: ffff8880b9d34c80
R13: ffff88801caeb880 R14: dffffc0000000000 R15: 0000000000000000
 finish_task_switch+0x145/0x620 kernel/sched/core.c:4191
 context_switch kernel/sched/core.c:4325 [inline]
 __schedule+0x9a1/0xe70 kernel/sched/core.c:5073
 schedule+0x14b/0x200 kernel/sched/core.c:5152
 freezable_schedule include/linux/freezer.h:172 [inline]
 do_nanosleep+0x1cd/0x740 kernel/time/hrtimer.c:1896
 hrtimer_nanosleep+0x1b9/0x3a0 kernel/time/hrtimer.c:1949
 __do_sys_clock_nanosleep kernel/time/posix-timers.c:1267 [inline]
 __se_sys_clock_nanosleep kernel/time/posix-timers.c:1245 [inline]
 __x64_sys_clock_nanosleep+0x2f6/0x340 kernel/time/posix-timers.c:1245
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x48a621
Code: 24 0c 89 3c 24 48 89 4c 24 18 e8 aa e7 ff ff 4c 8b 54 24 18 48 8b 54 24 10 41 89 c0 8b 74 24 0c 8b 3c 24 b8 e6 00 00 00 0f 05 <44> 89 c7 48 89 04 24 e8 e3 e7 ff ff 48 8b 04 24 eb 97 66 2e 0f 1f
RSP: 002b:00007ffd2ecab5c0 EFLAGS: 00000293 ORIG_RAX: 00000000000000e6
RAX: ffffffffffffffda RBX: 0000000000000008 RCX: 000000000048a621
RDX: 00007ffd2ecab600 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007ffd2ecab69c R08: 0000000000000000 R09: 0000000000000010
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000032
R13: 000000000006640a R14: 000000000000000d R15: 00007ffd2ecab700
================================================================================