Message-ID: <68f6a4c8.050a0220.1be48.0011.GAE@google.com>
Date: Mon, 20 Oct 2025 14:08:24 -0700
From: syzbot <syzbot+b0cff308140f79a9c4cb@...kaller.appspotmail.com>
To: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org, 
	chandna.sahil@...il.com, daniel@...earbox.net, eddyz87@...il.com, 
	haoluo@...gle.com, john.fastabend@...il.com, jolsa@...nel.org, 
	kpsingh@...nel.org, linux-kernel@...r.kernel.org, listout@...tout.xyz, 
	martin.lau@...ux.dev, netdev@...r.kernel.org, sdf@...ichev.me, 
	song@...nel.org, syzkaller-bugs@...glegroups.com, yonghong.song@...ux.dev
Subject: [syzbot] [bpf?] WARNING in bpf_bprintf_prepare (3)

Hello,

syzbot found the following issue on:

HEAD commit:    a1e83d4c0361 selftests/bpf: Fix redefinition of 'off' as d..
git tree:       bpf
console output: https://syzkaller.appspot.com/x/log.txt?x=12d21de2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9ad7b090a18654a7
dashboard link: https://syzkaller.appspot.com/bug?extid=b0cff308140f79a9c4cb
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=160cf542580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=128d5c58580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2f6a7a0cd1b7/disk-a1e83d4c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/873984cfc71e/vmlinux-a1e83d4c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/16711d84070c/bzImage-a1e83d4c.xz

The issue was bisected to:

commit 7c33e97a6ef5d84e98b892c3e00c6d1678d20395
Author: Sahil Chandna <chandna.sahil@...il.com>
Date:   Tue Oct 14 18:56:35 2025 +0000

    bpf: Do not disable preemption in bpf_test_run().

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=172fe492580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=14afe492580000
console output: https://syzkaller.appspot.com/x/log.txt?x=10afe492580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b0cff308140f79a9c4cb@...kaller.appspotmail.com
Fixes: 7c33e97a6ef5 ("bpf: Do not disable preemption in bpf_test_run().")

------------[ cut here ]------------
WARNING: CPU: 1 PID: 6145 at kernel/bpf/helpers.c:781 bpf_try_get_buffers kernel/bpf/helpers.c:781 [inline]
WARNING: CPU: 1 PID: 6145 at kernel/bpf/helpers.c:781 bpf_bprintf_prepare+0x12cf/0x13a0 kernel/bpf/helpers.c:834
Modules linked in:
CPU: 1 UID: 0 PID: 6145 Comm: syz.4.53 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:bpf_try_get_buffers kernel/bpf/helpers.c:781 [inline]
RIP: 0010:bpf_bprintf_prepare+0x12cf/0x13a0 kernel/bpf/helpers.c:834
Code: ff e9 ce fe ff ff e8 10 ec e0 ff e9 be fe ff ff e8 06 ec e0 ff e9 b4 fe ff ff e8 fc eb e0 ff e9 aa fe ff ff e8 f2 eb e0 ff 90 <0f> 0b 90 65 ff 0d 27 fd b2 10 b8 f0 ff ff ff e9 17 ff ff ff e8 d8
RSP: 0018:ffffc90003797840 EFLAGS: 00010293
RAX: ffffffff81df57fe RBX: ffffc90003797a10 RCX: ffff888026493c80
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000003
RBP: ffffc90003797970 R08: 0000000000585870 R09: 0000000000000005
R10: dffffc0000000000 R11: fffff520006f2f20 R12: dffffc0000000000
R13: 0000000000000004 R14: 0000000000000003 R15: 1ffff920006f2f42
FS:  00005555805f5500(0000) GS:ffff888125e0c000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000007c04e000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 ____bpf_trace_printk kernel/trace/bpf_trace.c:372 [inline]
 bpf_trace_printk+0xdb/0x190 kernel/trace/bpf_trace.c:362
 bpf_prog_bfbd7bf4bf171090+0x41/0x5a
 bpf_dispatcher_nop_func include/linux/bpf.h:1350 [inline]
 __bpf_prog_run include/linux/filter.h:721 [inline]
 bpf_prog_run include/linux/filter.h:728 [inline]
 bpf_prog_run_pin_on_cpu include/linux/filter.h:745 [inline]
 bpf_flow_dissect+0x225/0x720 net/core/flow_dissector.c:1024
 bpf_prog_test_run_flow_dissector+0x37c/0x5c0 net/bpf/test_run.c:1414
 bpf_prog_test_run+0x2c7/0x340 kernel/bpf/syscall.c:4688
 __sys_bpf+0x562/0x860 kernel/bpf/syscall.c:6167
 __do_sys_bpf kernel/bpf/syscall.c:6259 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6257 [inline]
 __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:6257
 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: 0033:0x7f25b0f8efc9
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:00007ffe036cd5e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f25b11e5fa0 RCX: 00007f25b0f8efc9
RDX: 0000000000000050 RSI: 0000200000000180 RDI: 000000000000000a
RBP: 00007f25b1011f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f25b11e5fa0 R14: 00007f25b11e5fa0 R15: 0000000000000003
 </TASK>


---
This report is generated by a bot. It may contain errors.
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection

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