Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <d520bd6c-bfd3-47f1-c794-ab451905256b@linux.dev>
Date:   Sun, 6 Aug 2023 23:40:04 -0700
MIME-Version: 1.0
Reply-To: yonghong.song@linux.dev
Subject: Re: [syzbot] [bpf?] KMSAN: uninit-value in
 ieee802154_subif_start_xmit
Content-Language: en-US
To:     syzbot <syzbot+d61b595e9205573133b3@syzkaller.appspotmail.com>,
        andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org,
        daniel@iogearbox.net, davem@davemloft.net, eddyz87@gmail.com,
        haoluo@google.com, hawk@kernel.org, john.fastabend@gmail.com,
        jolsa@kernel.org, kpsingh@kernel.org, kuba@kernel.org,
        linux-kernel@vger.kernel.org, martin.lau@linux.dev,
        netdev@vger.kernel.org, sdf@google.com, song@kernel.org,
        syzkaller-bugs@googlegroups.com
References: <0000000000002098bc0602496cc3@google.com>
From:   Yonghong Song <yonghong.song@linux.dev>
In-Reply-To: <0000000000002098bc0602496cc3@google.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk


On 8/6/23 4:23 PM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    25ad10658dc1 riscv, bpf: Adapt bpf trampoline to optimized..
> git tree:       bpf-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=147cbb29a80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=8acaeb93ad7c6aaa
> dashboard link: https://syzkaller.appspot.com/bug?extid=d61b595e9205573133b3
> 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=14d73ccea80000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1276aedea80000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/3d378cc13d42/disk-25ad1065.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/44580fd5d1af/vmlinux-25ad1065.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/840587618b41/bzImage-25ad1065.xz
> 
> The issue was bisected to:
> 
> commit 8100928c881482a73ed8bd499d602bab0fe55608
> Author: Yonghong Song <yonghong.song@linux.dev>
> Date:   Fri Jul 28 01:12:02 2023 +0000
> 
>      bpf: Support new sign-extension mov insns

Thanks for reporting. I will look into this ASAP.

> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17970c5da80000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=14570c5da80000
> console output: https://syzkaller.appspot.com/x/log.txt?x=10570c5da80000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d61b595e9205573133b3@syzkaller.appspotmail.com
> Fixes: 8100928c8814 ("bpf: Support new sign-extension mov insns")
> 
> general protection fault, probably for non-canonical address 0xdffffc0000000f4f: 0000 [#1] PREEMPT SMP KASAN
> KASAN: probably user-memory-access in range [0x0000000000007a78-0x0000000000007a7f]
> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.5.0-rc2-syzkaller-00619-g25ad10658dc1 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2023
> RIP: 0010:strnchr+0x25/0x80 lib/string.c:403
> Code: 00 00 00 00 90 f3 0f 1e fa 53 48 01 fe 48 bb 00 00 00 00 00 fc ff df 48 83 ec 18 eb 28 48 89 f8 48 89 f9 48 c1 e8 03 83 e1 07 <0f> b6 04 18 38 c8 7f 04 84 c0 75 25 0f b6 07 38 d0 74 15 48 83 c7
> RSP: 0018:ffffc90000177848 EFLAGS: 00010046
> RAX: 0000000000000f4f RBX: dffffc0000000000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000007a7b RDI: 0000000000007a78
> RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000003 R11: 0000000000000000 R12: 0000000000007a78
> R13: ffffc900001779b0 R14: 0000000000000000 R15: 0000000000000003
> FS:  0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00005611db5094b8 CR3: 0000000028ef0000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   <TASK>
>   bpf_bprintf_prepare+0x127/0x1490 kernel/bpf/helpers.c:823
>   ____bpf_trace_printk kernel/trace/bpf_trace.c:385 [inline]
>   bpf_trace_printk+0xdb/0x180 kernel/trace/bpf_trace.c:375
>   bpf_prog_ebeed182d92b487f+0x38/0x3c
>   bpf_dispatcher_nop_func include/linux/bpf.h:1180 [inline]
>   __bpf_prog_run include/linux/filter.h:609 [inline]
>   bpf_prog_run include/linux/filter.h:616 [inline]
>   __bpf_trace_run kernel/trace/bpf_trace.c:2269 [inline]
>   bpf_trace_run1+0x148/0x400 kernel/trace/bpf_trace.c:2307
>   __bpf_trace_rcu_utilization+0x8e/0xc0 include/trace/events/rcu.h:27
>   trace_rcu_utilization+0xcd/0x120 include/trace/events/rcu.h:27
>   rcu_note_context_switch+0x6c/0x1ac0 kernel/rcu/tree_plugin.h:318
>   __schedule+0x293/0x59f0 kernel/sched/core.c:6610
>   schedule_idle+0x5b/0x80 kernel/sched/core.c:6814
>   do_idle+0x288/0x3f0 kernel/sched/idle.c:310
>   cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:379
>   start_secondary+0x200/0x290 arch/x86/kernel/smpboot.c:326
>   secondary_startup_64_no_verify+0x167/0x16b
>   </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:strnchr+0x25/0x80 lib/string.c:403
> Code: 00 00 00 00 90 f3 0f 1e fa 53 48 01 fe 48 bb 00 00 00 00 00 fc ff df 48 83 ec 18 eb 28 48 89 f8 48 89 f9 48 c1 e8 03 83 e1 07 <0f> b6 04 18 38 c8 7f 04 84 c0 75 25 0f b6 07 38 d0 74 15 48 83 c7
> RSP: 0018:ffffc90000177848 EFLAGS: 00010046
> 
> RAX: 0000000000000f4f RBX: dffffc0000000000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000007a7b RDI: 0000000000007a78
> RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000003 R11: 0000000000000000 R12: 0000000000007a78
> R13: ffffc900001779b0 R14: 0000000000000000 R15: 0000000000000003
> FS:  0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00005611db5094b8 CR3: 0000000028ef0000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
>     0:	00 00                	add    %al,(%rax)
>     2:	00 00                	add    %al,(%rax)
>     4:	90                   	nop
>     5:	f3 0f 1e fa          	endbr64
>     9:	53                   	push   %rbx
>     a:	48 01 fe             	add    %rdi,%rsi
>     d:	48 bb 00 00 00 00 00 	movabs $0xdffffc0000000000,%rbx
>    14:	fc ff df
>    17:	48 83 ec 18          	sub    $0x18,%rsp
>    1b:	eb 28                	jmp    0x45
>    1d:	48 89 f8             	mov    %rdi,%rax
>    20:	48 89 f9             	mov    %rdi,%rcx
>    23:	48 c1 e8 03          	shr    $0x3,%rax
>    27:	83 e1 07             	and    $0x7,%ecx
> * 2a:	0f b6 04 18          	movzbl (%rax,%rbx,1),%eax <-- trapping instruction
>    2e:	38 c8                	cmp    %cl,%al
>    30:	7f 04                	jg     0x36
>    32:	84 c0                	test   %al,%al
>    34:	75 25                	jne    0x5b
>    36:	0f b6 07             	movzbl (%rdi),%eax
>    39:	38 d0                	cmp    %dl,%al
>    3b:	74 15                	je     0x52
>    3d:	48                   	rex.W
>    3e:	83                   	.byte 0x83
>    3f:	c7                   	.byte 0xc7
> 
> 
[...]