[syzbot] [bpf?] WARNING in bpf_mprog_pos_before

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 81335f90e8a8 bpf: unconditionally reset backtrack_state ma..
git tree: bpf
console+strace: https://syzkaller.appspot.com/x/log.txt?x=111d5132680000
kernel config: https://syzkaller.appspot.com/x/.config?x=f4894cf58531f
dashboard link: https://syzkaller.appspot.com/bug?extid=b97d20ed568ce0951a06
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1570bfc1680000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=126c6856680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/15d122573dad/disk-81335f90.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/74edf542067b/vmlinux-81335f90.xz
kernel image: https://storage.googleapis.com/syzbot-assets/22fa248ded38/bzImage-81335f90.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b97d20...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 5108 at include/linux/bpf_mprog.h:198 bpf_mprog_total include/linux/bpf_mprog.h:198 [inline]
WARNING: CPU: 0 PID: 5108 at include/linux/bpf_mprog.h:198 bpf_mprog_pos_before+0x18c/0x280 kernel/bpf/mprog.c:200
Modules linked in:
CPU: 0 PID: 5108 Comm: syz-executor123 Not tainted 6.6.0-rc1-syzkaller-00198-g81335f90e8a8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
RIP: 0010:bpf_mprog_total include/linux/bpf_mprog.h:198 [inline]
RIP: 0010:bpf_mprog_pos_before+0x18c/0x280 kernel/bpf/mprog.c:200
Code: 89 e8 48 c1 e8 03 42 80 3c 38 00 0f 85 d8 00 00 00 4d 3b 65 00 0f 85 26 ff ff ff e8 3e 50 e3 ff 83 eb 01 eb 38 e8 34 50 e3 ff <0f> 0b e9 3a ff ff ff e8 28 50 e3 ff 4c 89 f2 48 b8 00 00 00 00 00
RSP: 0018:ffffc90003aafad0 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88801e873b80 RSI: ffffffff81a47e4c RDI: 0000000000000005
RBP: 0000000000000040 R08: 0000000000000005 R09: 000000000000003f
R10: 0000000000000040 R11: 0000000000000000 R12: 0000000000000000
R13: ffff88801fdb0418 R14: ffffc90003aafb98 R15: dffffc0000000000
FS: 0000555556eea380(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8e2323b0d0 CR3: 00000000750ca000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
bpf_mprog_attach+0x720/0xfe0 kernel/bpf/mprog.c:258
tcx_prog_attach+0x2bd/0xbd0 kernel/bpf/tcx.c:39
bpf_prog_attach kernel/bpf/syscall.c:3848 [inline]
__sys_bpf+0x413e/0x4e90 kernel/bpf/syscall.c:5344
__do_sys_bpf kernel/bpf/syscall.c:5439 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5437 [inline]
__x64_sys_bpf+0x78/0xc0 kernel/bpf/syscall.c:5437
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f8e231c3cb9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc80795988 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f8e231c3cb9
RDX: 0000000000000020 RSI: 0000000020000080 RDI: 0000000000000008
RBP: 0000000000000000 R08: 0000000000000006 R09: 0000000000000006
R10: 0000000000000006 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000001
</TASK>


---
This report is generated by a bot. It may contain errors.
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[syzbot]

syzbot has bisected this issue to:

commit e420bed025071a623d2720a92bc2245c84757ecb
Author: Daniel Borkmann <dan...@iogearbox.net>
Date: Wed Jul 19 14:08:52 2023 +0000

bpf: Add fd-based tcx multi-prog infra with link support

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=116ab4b6680000
start commit: a59addacf899 drivers/net: process the result of hdlc_open(..
git tree: net
final oops: https://syzkaller.appspot.com/x/report.txt?x=136ab4b6680000
console output: https://syzkaller.appspot.com/x/log.txt?x=156ab4b6680000
kernel config: https://syzkaller.appspot.com/x/.config?x=d594086f139d167
dashboard link: https://syzkaller.appspot.com/bug?extid=b97d20ed568ce0951a06
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10dc3946680000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=107f4e1e680000

Reported-by: syzbot+b97d20...@syzkaller.appspotmail.com
Fixes: e420bed02507 ("bpf: Add fd-based tcx multi-prog infra with link support")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[syzbot]

> On 9/26/23 10:47 PM, syzbot wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit: 81335f90e8a8 bpf: unconditionally reset backtrack_state ma..
>> git tree: bpf
>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=111d5132680000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=f4894cf58531f
>> dashboard link: https://syzkaller.appspot.com/bug?extid=b97d20ed568ce0951a06
>> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1570bfc1680000
>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=126c6856680000
>>
>> Downloadable assets:
>> disk image: https://storage.googleapis.com/syzbot-assets/15d122573dad/disk-81335f90.raw.xz
>> vmlinux: https://storage.googleapis.com/syzbot-assets/74edf542067b/vmlinux-81335f90.xz
>> kernel image: https://storage.googleapis.com/syzbot-assets/22fa248ded38/bzImage-81335f90.xz
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+b97d20...@syzkaller.appspotmail.com
>

> #syz test: https://github.com/cilium/linux.git pr/mprog-fix

Your commands are accepted, but please keep syzkall...@googlegroups.com mailing list in CC next time. It serves as a history of what happened with each bug report. Thank you.

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+b97d20...@syzkaller.appspotmail.com

Tested on:

commit: 8fba38b8 selftest/bpf: Add various selftests for progr..
git tree: https://github.com/cilium/linux.git pr/mprog-fix
console output: https://syzkaller.appspot.com/x/log.txt?x=114a2a8a680000

kernel config: https://syzkaller.appspot.com/x/.config?x=f4894cf58531f
dashboard link: https://syzkaller.appspot.com/bug?extid=b97d20ed568ce0951a06
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.