Re: [syzbot] [bpf?] general protection fault in bpf_struct_ops_find_value

[Martin KaFai Lau]

On 1/25/24 9:53 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=11479fe7e80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=719e6acaf392d56b
> dashboard link: https://syzkaller.appspot.com/bug?extid=88f0aafe5f950d7489d7
> 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=14ea6be3e80000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15bc199be80000
>
> 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
>
> The issue was bisected to:
>
> commit fcc2c1fb0651477c8ed78a3a293c175ccd70697a
> Author: Kui-Feng Lee <thinker.li@xxxxxxxxx>
> Date:   Fri Jan 19 22:49:59 2024 +0000
>
>      bpf: pass attached BTF to the bpf_struct_ops subsystem
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=106a04c3e80000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=126a04c3e80000
> console output: https://syzkaller.appspot.com/x/log.txt?x=146a04c3e80000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+88f0aafe5f950d7489d7@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: fcc2c1fb0651 ("bpf: pass attached BTF to the bpf_struct_ops subsystem")
>
> general protection fault, probably for non-canonical address 0xdffffc0000000011: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000088-0x000000000000008f]
> CPU: 0 PID: 5058 Comm: syz-executor257 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:bpf_struct_ops_find_value+0x49/0x140 kernel/bpf/btf.c:8763
> Code: 7d ea dd ff 45 85 e4 0f 84 d7 00 00 00 e8 ff ee dd ff 48 8d bb 88 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 dc 00 00 00 48 8b 9b 88 00 00 00 48 85 db 0f 84
> RSP: 0018:ffffc90003bb7b20 EFLAGS: 00010206
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff81aa3283
> RDX: 0000000000000011 RSI: ffffffff81aa3291 RDI: 0000000000000088
> RBP: ffffc90003bb7dd0 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000002 R11: 0000000000000000 R12: 0000000000000002
> R13: 000000000000001a R14: ffffffff8ad6bca0 R15: ffffc90003bb7e04
> FS:  0000555556ed2380(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000000160d398 CR3: 000000007809c000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   <TASK>
>   bpf_struct_ops_map_alloc+0x12f/0x5d0 kernel/bpf/bpf_struct_ops.c:674

The check should be IS_ERR_"OR_NULL"(btf).  Kui-Feng, please take a look. Thanks.

>   map_create+0x548/0x1b90 kernel/bpf/syscall.c:1237
>   __sys_bpf+0xa32/0x4a00 kernel/bpf/syscall.c:5445
>   __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: 0033:0x7f9f205ef2e9
> 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:00007fffa4ce4088 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: 00007fffa4ce4268 RCX: 00007f9f205ef2e9
> RDX: 0000000000000048 RSI: 00000000200004c0 RDI: 0000000000000000
> RBP: 00007f9f20662610 R08: 0000000000000000 R09: 0000000000000000
> R10: 00000000ffffffff R11: 0000000000000246 R12: 0000000000000001
> R13: 00007fffa4ce4258 R14: 0000000000000001 R15: 0000000000000001
>   </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:bpf_struct_ops_find_value+0x49/0x140 kernel/bpf/btf.c:8763
> Code: 7d ea dd ff 45 85 e4 0f 84 d7 00 00 00 e8 ff ee dd ff 48 8d bb 88 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 dc 00 00 00 48 8b 9b 88 00 00 00 48 85 db 0f 84
> RSP: 0018:ffffc90003bb7b20 EFLAGS: 00010206
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff81aa3283
> RDX: 0000000000000011 RSI: ffffffff81aa3291 RDI: 0000000000000088
> RBP: ffffc90003bb7dd0 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000002 R11: 0000000000000000 R12: 0000000000000002
> R13: 000000000000001a R14: ffffffff8ad6bca0 R15: ffffc90003bb7e04
> FS:  0000555556ed2380(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000000160d398 CR3: 000000007809c000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess), 4 bytes skipped:
>     0:	45 85 e4             	test   %r12d,%r12d
>     3:	0f 84 d7 00 00 00    	je     0xe0
>     9:	e8 ff ee dd ff       	call   0xffddef0d
>     e:	48 8d bb 88 00 00 00 	lea    0x88(%rbx),%rdi
>    15:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
>    1c:	fc ff df
>    1f:	48 89 fa             	mov    %rdi,%rdx
>    22:	48 c1 ea 03          	shr    $0x3,%rdx
> * 26:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
>    2a:	0f 85 dc 00 00 00    	jne    0x10c
>    30:	48 8b 9b 88 00 00 00 	mov    0x88(%rbx),%rbx
>    37:	48 85 db             	test   %rbx,%rbx
>    3a:	0f                   	.byte 0xf
>    3b:	84                   	.byte 0x84
>
>
> ---
> 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@xxxxxxxxxxxxxxxx.
>
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> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>
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