Re: [syzbot] [bpf?] KMSAN: uninit-value in ieee802154_subif_start_xmit

From: Yonghong Song
Date: Mon Aug 07 2023 - 02:40:24 EST



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@xxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxxxxxxx
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


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