linux-kernel - Re: [syzbot] [bpf?] KMSAN: uninit-value in htab_lru_percpu_map_lookup

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Message-ID: <64666a8e-97fe-49b2-82f1-6469e3411746@linux.dev>
Date: Mon, 8 Apr 2024 15:12:45 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: syzbot <syzbot+b8d77b9bb107fa1bd641@...kaller.appspotmail.com>
Cc: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
 daniel@...earbox.net, eddyz87@...il.com, haoluo@...gle.com,
 john.fastabend@...il.com, jolsa@...nel.org, kpsingh@...nel.org,
 linux-kernel@...r.kernel.org, sdf@...gle.com, song@...nel.org,
 syzkaller-bugs@...glegroups.com, yonghong.song@...ux.dev
Subject: Re: [syzbot] [bpf?] KMSAN: uninit-value in
 htab_lru_percpu_map_lookup_elem

On 4/6/24 9:59 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    026e680b0a08 Merge tag 'pwm/for-6.9-rc3-fixes' of git://gi..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=173c55e5180000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=5112b3f484393436
> dashboard link: https://syzkaller.appspot.com/bug?extid=b8d77b9bb107fa1bd641
> 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=1495512d180000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=143c2415180000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/3b5659d2008c/disk-026e680b.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/7fd1552fafde/vmlinux-026e680b.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/ba622b1b0ec4/bzImage-026e680b.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b8d77b9bb107fa1bd641@...kaller.appspotmail.com
> 
> =====================================================
> BUG: KMSAN: uninit-value in __htab_map_lookup_elem kernel/bpf/hashtab.c:691 [inline]
> BUG: KMSAN: uninit-value in htab_lru_percpu_map_lookup_elem+0x39a/0x580 kernel/bpf/hashtab.c:2326
>   __htab_map_lookup_elem kernel/bpf/hashtab.c:691 [inline]
>   htab_lru_percpu_map_lookup_elem+0x39a/0x580 kernel/bpf/hashtab.c:2326
>   ____bpf_map_lookup_elem kernel/bpf/helpers.c:42 [inline]
>   bpf_map_lookup_elem+0x5c/0x80 kernel/bpf/helpers.c:38
>   ___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:1997
>   __bpf_prog_run64+0xb5/0xe0 kernel/bpf/core.c:2236
>   bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
>   __bpf_prog_run include/linux/filter.h:657 [inline]
>   bpf_prog_run include/linux/filter.h:664 [inline]
>   __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
>   bpf_trace_run2+0x116/0x300 kernel/trace/bpf_trace.c:2420
>   __bpf_trace_kfree+0x29/0x40 include/trace/events/kmem.h:94
>   trace_kfree include/trace/events/kmem.h:94 [inline]
>   kfree+0x6a5/0xa30 mm/slub.c:4377
>   kvfree+0x69/0x80 mm/util.c:680
>   __bpf_prog_put_rcu+0x37/0xf0 kernel/bpf/syscall.c:2232
>   rcu_do_batch kernel/rcu/tree.c:2196 [inline]
>   rcu_core+0xa59/0x1e70 kernel/rcu/tree.c:2471
>   rcu_core_si+0x12/0x20 kernel/rcu/tree.c:2488
>   __do_softirq+0x1c0/0x7d7 kernel/softirq.c:554
>   invoke_softirq kernel/softirq.c:428 [inline]
>   __irq_exit_rcu kernel/softirq.c:633 [inline]
>   irq_exit_rcu+0x6a/0x130 kernel/softirq.c:645
>   instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
>   sysvec_apic_timer_interrupt+0x83/0x90 arch/x86/kernel/apic/apic.c:1043
>   asm_sysvec_apic_timer_interrupt+0x1f/0x30 arch/x86/include/asm/idtentry.h:702
>   __preempt_count_dec_and_test arch/x86/include/asm/preempt.h:94 [inline]
>   flush_tlb_mm_range+0x294/0x320 arch/x86/mm/tlb.c:1036
>   flush_tlb_page arch/x86/include/asm/tlbflush.h:254 [inline]
>   ptep_clear_flush+0x166/0x1c0 mm/pgtable-generic.c:101
>   wp_page_copy mm/memory.c:3329 [inline]
>   do_wp_page+0x419d/0x66e0 mm/memory.c:3660
>   handle_pte_fault mm/memory.c:5316 [inline]
>   __handle_mm_fault mm/memory.c:5441 [inline]
>   handle_mm_fault+0x5b76/0xce00 mm/memory.c:5606
>   do_user_addr_fault arch/x86/mm/fault.c:1362 [inline]
>   handle_page_fault arch/x86/mm/fault.c:1505 [inline]
>   exc_page_fault+0x419/0x730 arch/x86/mm/fault.c:1563
>   asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:623
> 
> Local variable stack created at:
>   __bpf_prog_run64+0x45/0xe0 kernel/bpf/core.c:2236
>   bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
>   __bpf_prog_run include/linux/filter.h:657 [inline]
>   bpf_prog_run include/linux/filter.h:664 [inline]
>   __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
>   bpf_trace_run2+0x116/0x300 kernel/trace/bpf_trace.c:2420
> 
> CPU: 1 PID: 5015 Comm: syz-executor232 Not tainted 6.9.0-rc2-syzkaller-00002-g026e680b0a08 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
> =====================================================

#syz dup: [syzbot] [bpf?] [net?] KMSAN: uninit-value in dev_map_lookup_elem