linux-kernel - Re: [syzbot] [bpf?] BUG: unable to handle kernel paging request in bpf_prog

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Date: Fri, 19 Apr 2024 12:44:04 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: syzbot <syzbot+838346b979830606c854@...kaller.appspotmail.com>, 
	Björn Töpel <bjorn@...nel.org>, 
	Stanislav Fomichev <sdf@...gle.com>
Cc: Andrii Nakryiko <andrii@...nel.org>, Alexei Starovoitov <ast@...nel.org>, bpf <bpf@...r.kernel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Eddy Z <eddyz87@...il.com>, Hao Luo <haoluo@...gle.com>, 
	John Fastabend <john.fastabend@...il.com>, Jiri Olsa <jolsa@...nel.org>, 
	KP Singh <kpsingh@...nel.org>, LKML <linux-kernel@...r.kernel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, 
	syzkaller-bugs <syzkaller-bugs@...glegroups.com>, Yonghong Song <yonghong.song@...ux.dev>
Subject: Re: [syzbot] [bpf?] BUG: unable to handle kernel paging request in
 bpf_prog_ADDR (2)

On Mon, Apr 8, 2024 at 8:53 PM syzbot
<syzbot+838346b979830606c854@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    fe46a7dd189e Merge tag 'sound-6.9-rc1' of git://git.kernel..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=12596223180000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4d90a36f0cab495a
> dashboard link: https://syzkaller.appspot.com/bug?extid=838346b979830606c854
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=134ecbb5180000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=141a8b3d180000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/f6c04726a2ae/disk-fe46a7dd.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/09c26ce901ea/vmlinux-fe46a7dd.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/134acf7f5322/bzImage-fe46a7dd.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+838346b979830606c854@...kaller.appspotmail.com
>
> BUG: unable to handle page fault for address: 0000001000000112
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 800000002e7b1067 P4D 800000002e7b1067 PUD 0
> Oops: 0000 [#1] PREEMPT SMP KASAN PTI
> CPU: 0 PID: 5060 Comm: syz-executor351 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
> RIP: 0010:bpf_prog_a8e24a805b35c61b+0x19/0x1e
> Code: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc f3 0f 1e fa 0f 1f 44 00 00 66 90 55 48 89 e5 f3 0f 1e fa 31 c0 48 8b 7f 18 <8b> 7f 00 c9 c3 cc cc cc cc cc cc 40 03 00 00 cc cc cc cc cc cc cc
> RSP: 0018:ffffc90003b07b30 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: ffffc90000ace048 RCX: ffff88802aa89e00
> RDX: 0000000000000000 RSI: ffffc90000ace048 RDI: 0000001000000112
> RBP: ffffc90003b07b30 R08: ffffffff81bf633c R09: 1ffffffff2595ca0
> R10: dffffc0000000000 R11: ffffffffa000095c R12: ffffc90000ace030
> R13: ffff88802ac3ae28 R14: dffffc0000000000 R15: ffff88802ac3ae28
> FS:  000055558f759380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000001000000112 CR3: 0000000077cfa000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
>  __bpf_prog_run include/linux/filter.h:657 [inline]
>  bpf_prog_run include/linux/filter.h:664 [inline]
>  bpf_prog_run_array_cg kernel/bpf/cgroup.c:51 [inline]
>  __cgroup_bpf_run_filter_setsockopt+0x6fa/0x1040 kernel/bpf/cgroup.c:1830
>  do_sock_setsockopt+0x6b4/0x720 net/socket.c:2293
>  __sys_setsockopt+0x1ae/0x250 net/socket.c:2334
>  __do_sys_setsockopt net/socket.c:2343 [inline]
>  __se_sys_setsockopt net/socket.c:2340 [inline]
>  __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2340
>  do_syscall_64+0xfb/0x240
>  entry_SYSCALL_64_after_hwframe+0x6d/0x75

This one looks interesting.
But I cannot reproduce it.

Bjorn or Stan,

Could you take a look?

Probably a race in xdp dispatcher setup or the way cgroup-lsm
logic is doing it.