[moderation] [kernel?] general protection fault in pick_next_entity

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 74fe02ce122a Merge tag 'wq-for-7.1-rc2-fixes' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1352ddba580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4caf64b1ee83dac0
dashboard link: https://syzkaller.appspot.com/bug?extid=d3bd77932b0f5df02c46
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [anna-...@linutronix.de fred...@kernel.org linux-...@vger.kernel.org tg...@kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b1158b5c4e12/disk-74fe02ce.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1c71d66e8174/vmlinux-74fe02ce.xz
kernel image: https://storage.googleapis.com/syzbot-assets/952f45da2726/bzImage-74fe02ce.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d3bd77...@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc000000000b: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000058-0x000000000000005f]
CPU: 0 UID: 0 PID: 7450 Comm: syz.3.519 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:pick_next_entity+0xca8/0xe90 kernel/sched/fair.c:5757
Code: 89 d8 48 c1 e8 03 42 80 3c 20 00 74 08 48 89 df e8 bd ea 97 00 4c 3b 33 79 05 48 8b 6c 24 40 48 8d 5d 59 48 89 d8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 75 61 80 3b 00 74 14 48 8b 7c 24 70 48 89 ee
RSP: 0018:ffffc9000594f1d0 EFLAGS: 00010002
RAX: 000000000000000b RBX: 0000000000000059 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff8880b863af00 RDI: ffff8880b863af50
RBP: 0000000000000000 R08: ffff88807c081ec7 R09: 1ffff1100f8103d8
R10: dffffc0000000000 R11: ffffed100f8103d9 R12: dffffc0000000000
R13: ffff8880b863af00 R14: 0000000000000000 R15: ffff8880b863af01
FS: 0000555594831500(0000) GS:ffff888125290000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000001e80 CR3: 0000000075766000 CR4: 00000000003526f0
Call Trace:
<TASK>
wakeup_preempt_fair+0x7a4/0xb60 kernel/sched/fair.c:9141
wakeup_preempt+0x162/0x300 kernel/sched/core.c:2248
attach_task kernel/sched/sched.h:3035 [inline]
attach_tasks kernel/sched/fair.c:10026 [inline]
sched_balance_rq+0x42c4/0x5a60 kernel/sched/fair.c:12164
sched_balance_newidle kernel/sched/fair.c:13239 [inline]
pick_next_task_fair+0xb3f/0x1ab0 kernel/sched/fair.c:9267
__pick_next_task+0xe6/0x480 kernel/sched/core.c:6019
pick_next_task kernel/sched/core.c:-1 [inline]
__schedule+0x974/0x5680 kernel/sched/core.c:7105
__schedule_loop kernel/sched/core.c:7268 [inline]
schedule+0x164/0x360 kernel/sched/core.c:7283
do_nanosleep+0x1c2/0x620 kernel/time/hrtimer.c:2293
hrtimer_nanosleep+0x18f/0x3a0 kernel/time/hrtimer.c:2339
__do_sys_clock_nanosleep kernel/time/posix-timers.c:1391 [inline]
__se_sys_clock_nanosleep+0x35b/0x3b0 kernel/time/posix-timers.c:1368
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb2cc15d60e
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007fb2cc53fb28 EFLAGS: 00000246 ORIG_RAX: 00000000000000e6
RAX: ffffffffffffffda RBX: 0000555594831500 RCX: 00007fb2cc15d60e
RDX: 00007fb2cc53fb80 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fb2cc417da0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000002fa01
R13: 00007fb2cc415fac R14: 000000000002ee7a R15: 00007fb2cc415fa0
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:pick_next_entity+0xca8/0xe90 kernel/sched/fair.c:5757
Code: 89 d8 48 c1 e8 03 42 80 3c 20 00 74 08 48 89 df e8 bd ea 97 00 4c 3b 33 79 05 48 8b 6c 24 40 48 8d 5d 59 48 89 d8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 75 61 80 3b 00 74 14 48 8b 7c 24 70 48 89 ee
RSP: 0018:ffffc9000594f1d0 EFLAGS: 00010002
RAX: 000000000000000b RBX: 0000000000000059 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff8880b863af00 RDI: ffff8880b863af50
RBP: 0000000000000000 R08: ffff88807c081ec7 R09: 1ffff1100f8103d8
R10: dffffc0000000000 R11: ffffed100f8103d9 R12: dffffc0000000000
R13: ffff8880b863af00 R14: 0000000000000000 R15: ffff8880b863af01
FS: 0000555594831500(0000) GS:ffff888125290000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000001e80 CR3: 0000000075766000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
0: 89 d8 mov %ebx,%eax
2: 48 c1 e8 03 shr $0x3,%rax
6: 42 80 3c 20 00 cmpb $0x0,(%rax,%r12,1)
b: 74 08 je 0x15
d: 48 89 df mov %rbx,%rdi
10: e8 bd ea 97 00 call 0x97ead2
15: 4c 3b 33 cmp (%rbx),%r14
18: 79 05 jns 0x1f
1a: 48 8b 6c 24 40 mov 0x40(%rsp),%rbp
1f: 48 8d 5d 59 lea 0x59(%rbp),%rbx
23: 48 89 d8 mov %rbx,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax <-- trapping instruction
2f: 84 c0 test %al,%al
31: 75 61 jne 0x94
33: 80 3b 00 cmpb $0x0,(%rbx)
36: 74 14 je 0x4c
38: 48 8b 7c 24 70 mov 0x70(%rsp),%rdi
3d: 48 89 ee mov %rbp,%rsi


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