Subject: Re: [syzbot] [perf?] WARNING in __perf_event_overflow (2)

From: syzbot <[email-masked]>
Date: Tue, 07 Oct 2025 09:18:26 -0700

syzbot has found a reproducer for the following issue on:

HEAD commit:    de7342228b73 bpf: Finish constification of 1st parameter o..
git tree:       bpf-next
console output: https://syzkaller.appspot.com/x/log.txt?x=16e75a7c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1e0e0bf7e51565cd
dashboard link: https://syzkaller.appspot.com/bug?extid=2524754f17993441bf66
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=167761e2580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16b941e2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/48d49cec8205/disk-de734222.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0c197aec9229/vmlinux-de734222.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7f7872725138/bzImage-de734222.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

------------[ cut here ]------------
WARNING: CPU: 1 PID: 6380 at kernel/events/core.c:10369 __perf_event_overflow+0xb3b/0xe40 kernel/events/core.c:10369
Modules linked in:
CPU: 1 UID: 0 PID: 6380 Comm: syz.3.105 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:__perf_event_overflow+0xb3b/0xe40 kernel/events/core.c:10369
Code: 08 4c 89 f7 e8 a6 f9 34 00 4d 89 3e e9 bc fa ff ff 48 c7 44 24 40 00 00 00 00 e8 d0 55 cf ff e9 1c fe ff ff e8 c6 55 cf ff 90 <0f> 0b 90 e9 2d ff ff ff e8 b8 55 cf ff 48 c7 c7 a0 fa 73 8b e8 ec
RSP: 0018:ffffc9000afd74c0 EFLAGS: 00010293
RAX: ffffffff81efce8a RBX: 1ffff1100b67a3b5 RCX: ffff8880572d0000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000afd75d0 R08: ffff88805b3d1b4f R09: 1ffff1100b67a369
R10: dffffc0000000000 R11: ffffed100b67a36a R12: dffffc0000000000
R13: ffff88805b3d1900 R14: ffff88805b3d1b48 R15: 0000000000000000
FS:  00007fd06a42e6c0(0000) GS:ffff888125e27000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000114bc000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 perf_swevent_overflow kernel/events/core.c:10467 [inline]
 perf_swevent_event+0x2f4/0x5e0 kernel/events/core.c:-1
 do_perf_sw_event kernel/events/core.c:10607 [inline]
 ___perf_sw_event+0x4a1/0x700 kernel/events/core.c:10634
 __perf_sw_event+0xfa/0x1a0 kernel/events/core.c:10646
 perf_sw_event include/linux/perf_event.h:1596 [inline]
 do_user_addr_fault+0x12d9/0x1380 arch/x86/mm/fault.c:1283
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0010:rep_movs_alternative+0x4a/0x90 arch/x86/lib/copy_user_64.S:74
Code: 35 04 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 8b 06 48 89 07 48 83 c6 08 48 83 c7 08 83 e9 08 74 db 83 f9 08 73 e8 eb c5 <f3> a4 e9 4f 35 04 00 48 8b 06 48 89 07 48 8d 47 08 48 83 e0 f8 48
RSP: 0018:ffffc9000afd7af0 EFLAGS: 00050202
RAX: 00007ffffffff001 RBX: 0000000000000060 RCX: 0000000000000060
RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffffc9000af0d060
RBP: 0000000000000000 R08: ffffc9000af0d0bf R09: 1ffff920015e1a17
R10: dffffc0000000000 R11: fffff520015e1a18 R12: ffffc9000af0d060
R13: dffffc0000000000 R14: ffffc9000af0d060 R15: 0000000000000000
 copy_user_generic arch/x86/include/asm/uaccess_64.h:126 [inline]
 raw_copy_from_user arch/x86/include/asm/uaccess_64.h:141 [inline]
 _inline_copy_from_user include/linux/uaccess.h:178 [inline]
 _copy_from_user+0x7a/0xb0 lib/usercopy.c:18
 copy_from_user include/linux/uaccess.h:212 [inline]
 copy_from_bpfptr_offset include/linux/bpfptr.h:53 [inline]
 copy_from_bpfptr+0x5c/0x90 include/linux/bpfptr.h:59
 bpf_prog_load+0xa83/0x19e0 kernel/bpf/syscall.c:2992
 __sys_bpf+0x507/0x860 kernel/bpf/syscall.c:6134
 __do_sys_bpf kernel/bpf/syscall.c:6244 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6242 [inline]
 __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:6242
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd06958eec9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd06a42e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007fd0697e5fa0 RCX: 00007fd06958eec9
RDX: 0000000000000094 RSI: 00002000000000c0 RDI: 0000000000000005
RBP: 00007fd069611f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd0697e6038 R14: 00007fd0697e5fa0 R15: 00007ffcf5bcab18
 </TASK>
----------------
Code disassembly (best guess):
   0:	35 04 00 66 2e       	xor    $0x2e660004,%eax
   5:	0f 1f 84 00 00 00 00 	nopl   0x0(%rax,%rax,1)
   c:	00
   d:	0f 1f 00             	nopl   (%rax)
  10:	48 8b 06             	mov    (%rsi),%rax
  13:	48 89 07             	mov    %rax,(%rdi)
  16:	48 83 c6 08          	add    $0x8,%rsi
  1a:	48 83 c7 08          	add    $0x8,%rdi
  1e:	83 e9 08             	sub    $0x8,%ecx
  21:	74 db                	je     0xfffffffe
  23:	83 f9 08             	cmp    $0x8,%ecx
  26:	73 e8                	jae    0x10
  28:	eb c5                	jmp    0xffffffef
* 2a:	f3 a4                	rep movsb %ds:(%rsi),%es:(%rdi) <-- trapping instruction
  2c:	e9 4f 35 04 00       	jmp    0x43580
  31:	48 8b 06             	mov    (%rsi),%rax
  34:	48 89 07             	mov    %rax,(%rdi)
  37:	48 8d 47 08          	lea    0x8(%rdi),%rax
  3b:	48 83 e0 f8          	and    $0xfffffffffffffff8,%rax
  3f:	48                   	rex.W

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