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SubjectRe: [syzbot] general protection fault in btf_decl_tag_resolve
From


On 2/2/22 7:36 PM, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: b7892f7d5cb2 tools: Ignore errors from `which' when search..
> git tree: bpf
> console output: https://syzkaller.appspot.com/x/log.txt?x=13181634700000
> kernel config: https://syzkaller.appspot.com/x/.config?x=5044676c290190f2
> dashboard link: https://syzkaller.appspot.com/bug?extid=53619be9444215e785ed
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16454914700000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16ceb884700000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+53619be9444215e785ed@syzkaller.appspotmail.com
>
> general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> CPU: 0 PID: 3592 Comm: syz-executor914 Not tainted 5.16.0-syzkaller-11424-gb7892f7d5cb2 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:btf_type_vlen include/linux/btf.h:231 [inline]
> RIP: 0010:btf_decl_tag_resolve+0x83e/0xaa0 kernel/bpf/btf.c:3910
> Code: c1 ea 03 80 3c 02 00 0f 85 90 01 00 00 48 8b 1b e8 b7 c9 e6 ff 48 8d 7b 04 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 2b
> RSP: 0018:ffffc90001b1fa00 EFLAGS: 00010247
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffffff81918c09 RDI: 0000000000000004
> RBP: ffff888015c32000 R08: 0000000000000008 R09: 0000000000000008
> R10: ffffffff81918bb1 R11: 0000000000000001 R12: 0000000000000004
> R13: 0000000000000008 R14: 0000000000000000 R15: 0000000000000005
> FS: 00005555556fd300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f98c38b8220 CR3: 0000000019537000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> btf_resolve+0x251/0x1020 kernel/bpf/btf.c:4198
> btf_check_all_types kernel/bpf/btf.c:4239 [inline]
> btf_parse_type_sec kernel/bpf/btf.c:4280 [inline]
> btf_parse kernel/bpf/btf.c:4513 [inline]
> btf_new_fd+0x19fe/0x2370 kernel/bpf/btf.c:6047
> bpf_btf_load kernel/bpf/syscall.c:4039 [inline]
> __sys_bpf+0x1cbb/0x5970 kernel/bpf/syscall.c:4679
> __do_sys_bpf kernel/bpf/syscall.c:4738 [inline]
> __se_sys_bpf kernel/bpf/syscall.c:4736 [inline]
> __x64_sys_bpf+0x75/0xb0 kernel/bpf/syscall.c:4736
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7fd57f202099
> Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 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 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffe9e5eb898 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fd57f202099
> RDX: 0000000000000020 RSI: 0000000020000000 RDI: 0000000000000012
> RBP: 00007fd57f1c6080 R08: 0000000000000000 R09: 0000000000000000
> R10: 00000000ffffffff R11: 0000000000000246 R12: 00007fd57f1c6110
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:btf_type_vlen include/linux/btf.h:231 [inline]
> RIP: 0010:btf_decl_tag_resolve+0x83e/0xaa0 kernel/bpf/btf.c:3910
> Code: c1 ea 03 80 3c 02 00 0f 85 90 01 00 00 48 8b 1b e8 b7 c9 e6 ff 48 8d 7b 04 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 2b
> RSP: 0018:ffffc90001b1fa00 EFLAGS: 00010247
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffffff81918c09 RDI: 0000000000000004
> RBP: ffff888015c32000 R08: 0000000000000008 R09: 0000000000000008
> R10: ffffffff81918bb1 R11: 0000000000000001 R12: 0000000000000004
> R13: 0000000000000008 R14: 0000000000000000 R15: 0000000000000005
> FS: 00005555556fd300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000000 CR3: 0000000019537000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
> 0: c1 ea 03 shr $0x3,%edx
> 3: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
> 7: 0f 85 90 01 00 00 jne 0x19d
> d: 48 8b 1b mov (%rbx),%rbx
> 10: e8 b7 c9 e6 ff callq 0xffe6c9cc
> 15: 48 8d 7b 04 lea 0x4(%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 14 02 movzbl (%rdx,%rax,1),%edx <-- trapping instruction
> 2e: 48 89 f8 mov %rdi,%rax
> 31: 83 e0 07 and $0x7,%eax
> 34: 83 c0 03 add $0x3,%eax
> 37: 38 d0 cmp %dl,%al
> 39: 7c 08 jl 0x43
> 3b: 84 d2 test %dl,%dl
> 3d: 0f .byte 0xf
> 3e: 85 2b test %ebp,(%rbx)
>
>
> ---
> 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:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches

Thanks for reporting. I am looking at this now.

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