Subject: Re: [syzbot] [bpf?] general protection fault in bpf_check (2)

From: Jiri Olsa <[email-masked]>
Date: Fri, 22 Mar 2024 22:44:42 +0100

On Fri, Mar 22, 2024 at 12:13:29PM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    ddb2ffdc474a libbpf: Define MFD_CLOEXEC if not available
> git tree:       bpf
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=14ba06a5180000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=6fb1be60a193d440
> dashboard link: https://syzkaller.appspot.com/bug?extid=ba82760c63ba37799f70
> 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=115671f1180000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14f14e31180000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/1e40c56954a9/disk-ddb2ffdc.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/738240a7f62b/vmlinux-ddb2ffdc.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/2b2e360f1d3a/bzImage-ddb2ffdc.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email-masked]
> 
> general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] PREEMPT SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]
> CPU: 1 PID: 5066 Comm: syz-executor115 Not tainted 6.8.0-syzkaller-05232-gddb2ffdc474a #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
> RIP: 0010:do_misc_fixups kernel/bpf/verifier.c:19609 [inline]
> RIP: 0010:bpf_check+0xa19b/0x19010 kernel/bpf/verifier.c:21294
> Code: 48 c1 e8 03 80 3c 08 00 74 12 48 89 df e8 2d 93 50 00 48 b9 00 00 00 00 00 fc ff df 48 8b 1b 48 83 c3 30 48 89 d8 48 c1 e8 03 <0f> b6 04 08 84 c0 0f 85 e3 4c 00 00 8b 1b be 00 00 04 00 21 de 31
> RSP: 0018:ffffc900039671e0 EFLAGS: 00010206
> RAX: 0000000000000006 RBX: 0000000000000030 RCX: dffffc0000000000
> RDX: ffff888018358000 RSI: 0000000000010000 RDI: 0000000000000001
> RBP: ffffc90003967b50 R08: ffffffff81a7a128 R09: ffffffff81a7a365
> R10: 0000000000000004 R11: ffff888018358000 R12: ffffc90000ace072
> R13: 1ffff92000159c0e R14: 1ffff92000159c0e R15: 0000000000010000
> FS:  000055555905c380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000111ed398 CR3: 000000002258e000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  bpf_prog_load+0x1667/0x20f0 kernel/bpf/syscall.c:2895
>  __sys_bpf+0x4ee/0x810 kernel/bpf/syscall.c:5631
>  __do_sys_bpf kernel/bpf/syscall.c:5738 [inline]
>  __se_sys_bpf kernel/bpf/syscall.c:5736 [inline]
>  __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5736
>  do_syscall_64+0xfb/0x240
>  entry_SYSCALL_64_after_hwframe+0x6d/0x75

looks like we might have a fix already:
  https://lore.kernel.org/bpf/[email-masked]/T/#u

jirka

> RIP: 0033:0x7f425974e3e9
> 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:00007ffe73dd9d38 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: 00007ffe73dd9f18 RCX: 00007f425974e3e9
> RDX: 0000000000000090 RSI: 00000000200000c0 RDI: 0000000000000005
> RBP: 00007f42597c1610 R08: 0000000000000000 R09: 0000000000000000
> R10: 00000000ffffffff R11: 0000000000000246 R12: 0000000000000001
> R13: 00007ffe73dd9f08 R14: 0000000000000001 R15: 0000000000000001
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:do_misc_fixups kernel/bpf/verifier.c:19609 [inline]
> RIP: 0010:bpf_check+0xa19b/0x19010 kernel/bpf/verifier.c:21294
> Code: 48 c1 e8 03 80 3c 08 00 74 12 48 89 df e8 2d 93 50 00 48 b9 00 00 00 00 00 fc ff df 48 8b 1b 48 83 c3 30 48 89 d8 48 c1 e8 03 <0f> b6 04 08 84 c0 0f 85 e3 4c 00 00 8b 1b be 00 00 04 00 21 de 31
> RSP: 0018:ffffc900039671e0 EFLAGS: 00010206
> RAX: 0000000000000006 RBX: 0000000000000030 RCX: dffffc0000000000
> RDX: ffff888018358000 RSI: 0000000000010000 RDI: 0000000000000001
> RBP: ffffc90003967b50 R08: ffffffff81a7a128 R09: ffffffff81a7a365
> R10: 0000000000000004 R11: ffff888018358000 R12: ffffc90000ace072
> R13: 1ffff92000159c0e R14: 1ffff92000159c0e R15: 0000000000010000
> FS:  000055555905c380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000111ed398 CR3: 000000002258e000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
>    0:	48 c1 e8 03          	shr    $0x3,%rax
>    4:	80 3c 08 00          	cmpb   $0x0,(%rax,%rcx,1)
>    8:	74 12                	je     0x1c
>    a:	48 89 df             	mov    %rbx,%rdi
>    d:	e8 2d 93 50 00       	call   0x50933f
>   12:	48 b9 00 00 00 00 00 	movabs $0xdffffc0000000000,%rcx
>   19:	fc ff df
>   1c:	48 8b 1b             	mov    (%rbx),%rbx
>   1f:	48 83 c3 30          	add    $0x30,%rbx
>   23:	48 89 d8             	mov    %rbx,%rax
>   26:	48 c1 e8 03          	shr    $0x3,%rax
> * 2a:	0f b6 04 08          	movzbl (%rax,%rcx,1),%eax <-- trapping instruction
>   2e:	84 c0                	test   %al,%al
>   30:	0f 85 e3 4c 00 00    	jne    0x4d19
>   36:	8b 1b                	mov    (%rbx),%ebx
>   38:	be 00 00 04 00       	mov    $0x40000,%esi
>   3d:	21 de                	and    %ebx,%esi
>   3f:	31                   	.byte 0x31
> 
> 
> ---
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