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Message-ID: <d6de99ca-64ca-4b21-958d-686efcd3acd8@linux.dev>
Date: Thu, 25 Jan 2024 10:02:03 -0800
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MIME-Version: 1.0
Subject: Re: [syzbot] [bpf?] general protection fault in btf_is_module
Content-Language: en-US
To: Kui-Feng Lee <thinker.li@gmail.com>
References: <00000000000026353b060fc21c07@google.com>
From: Martin KaFai Lau <martin.lau@linux.dev>
Cc: syzbot <syzbot+1336f3d4b10bcda75b89@syzkaller.appspotmail.com>,
 andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org,
 daniel@iogearbox.net, haoluo@google.com, john.fastabend@gmail.com,
 jolsa@kernel.org, kpsingh@kernel.org, linux-kernel@vger.kernel.org,
 netdev@vger.kernel.org, sdf@google.com, song@kernel.org,
 syzkaller-bugs@googlegroups.com, yonghong.song@linux.dev
In-Reply-To: <00000000000026353b060fc21c07@google.com>
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On 1/25/24 1:50 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    d47b9f68d289 libbpf: Correct bpf_core_read.h comment wrt b..
> git tree:       bpf-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=104b1ef7e80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=719e6acaf392d56b
> dashboard link: https://syzkaller.appspot.com/bug?extid=1336f3d4b10bcda75b89
> 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=10c1a53be80000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1052cec3e80000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/1a9b4a5622fb/disk-d47b9f68.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/dd68baeac4fd/vmlinux-d47b9f68.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/811ba9dc9ddf/bzImage-d47b9f68.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+1336f3d4b10bcda75b89@syzkaller.appspotmail.com
> 
> general protection fault, probably for non-canonical address 0xdffffc000000001b: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x00000000000000d8-0x00000000000000df]
> CPU: 0 PID: 5064 Comm: syz-executor334 Not tainted 6.7.0-syzkaller-12348-gd47b9f68d289 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
> RIP: 0010:btf_is_module+0x26/0x80 kernel/bpf/btf.c:7441
> Code: 00 eb f0 90 66 0f 1f 00 55 53 48 89 fb e8 92 24 de ff 48 8d bb d8 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 02 7e 48 0f b6 ab d8 00 00 00 31 ff 89 ee e8
> RSP: 0018:ffffc900039ff828 EFLAGS: 00010206
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff81a07f47
> RDX: 000000000000001b RSI: ffffffff81a9fcfe RDI: 00000000000000d8
> RBP: ffffc900039ffaf0 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000000004 R11: ffffffff8aa0008b R12: ffffc90000ae6038
> R13: ffffc90000ae6000 R14: 0000000000000000 R15: 0000000000000000
> FS:  000055555660b380(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000001b6b398 CR3: 000000001aaae000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   <TASK>
>   check_struct_ops_btf_id kernel/bpf/verifier.c:20302 [inline]

Kui-Feng, it should be due to the commit e3f87fdfed7b ("bpf: hold module refcnt 
in bpf_struct_ops map creation and prog verification."). I think it needs a NULL 
check on the return value from bpf_get_btf_vmlinux().

Please take a look. Thanks.


>   check_attach_btf_id kernel/bpf/verifier.c:20730 [inline]
>   bpf_check+0x6cfe/0x9df0 kernel/bpf/verifier.c:20898
>   bpf_prog_load+0x14dc/0x2310 kernel/bpf/syscall.c:2769
>   __sys_bpf+0xbf7/0x4a00 kernel/bpf/syscall.c:5463
>   __do_sys_bpf kernel/bpf/syscall.c:5567 [inline]
>   __se_sys_bpf kernel/bpf/syscall.c:5565 [inline]
>   __x64_sys_bpf+0x78/0xc0 kernel/bpf/syscall.c:5565
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xd3/0x250 arch/x86/entry/common.c:83
>   entry_SYSCALL_64_after_hwframe+0x63/0x6b
> RIP: 0033:0x7f4dbbe514a9
> Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffe76acbe18 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: 00007ffe76acbff8 RCX: 00007f4dbbe514a9
> RDX: 00000000000000a0 RSI: 00000000200009c0 RDI: 0000000000000005
> RBP: 00007f4dbbec4610 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
> R13: 00007ffe76acbfe8 R14: 0000000000000001 R15: 0000000000000001
>   </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:btf_is_module+0x26/0x80 kernel/bpf/btf.c:7441
> Code: 00 eb f0 90 66 0f 1f 00 55 53 48 89 fb e8 92 24 de ff 48 8d bb d8 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 02 7e 48 0f b6 ab d8 00 00 00 31 ff 89 ee e8
> RSP: 0018:ffffc900039ff828 EFLAGS: 00010206
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff81a07f47
> RDX: 000000000000001b RSI: ffffffff81a9fcfe RDI: 00000000000000d8
> RBP: ffffc900039ffaf0 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000000004 R11: ffffffff8aa0008b R12: ffffc90000ae6038
> R13: ffffc90000ae6000 R14: 0000000000000000 R15: 0000000000000000
> FS:  000055555660b380(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000001b6b398 CR3: 000000001aaae000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
>     0:	00 eb                	add    %ch,%bl
>     2:	f0 90                	lock nop
>     4:	66 0f 1f 00          	nopw   (%rax)
>     8:	55                   	push   %rbp
>     9:	53                   	push   %rbx
>     a:	48 89 fb             	mov    %rdi,%rbx
>     d:	e8 92 24 de ff       	call   0xffde24a4
>    12:	48 8d bb d8 00 00 00 	lea    0xd8(%rbx),%rdi
>    19:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
>    20:	fc ff df
>    23:	48 89 fa             	mov    %rdi,%rdx
>    26:	48 c1 ea 03          	shr    $0x3,%rdx
> * 2a:	0f b6 04 02          	movzbl (%rdx,%rax,1),%eax <-- trapping instruction
>    2e:	84 c0                	test   %al,%al
>    30:	74 02                	je     0x34
>    32:	7e 48                	jle    0x7c
>    34:	0f b6 ab d8 00 00 00 	movzbl 0xd8(%rbx),%ebp
>    3b:	31 ff                	xor    %edi,%edi
>    3d:	89 ee                	mov    %ebp,%esi
>    3f:	e8                   	.byte 0xe8
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
> 
> syzbot will keep track of this issue. See:
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> 
> If the report is already addressed, let syzbot know by replying with:
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> 
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> 
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> 
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