Re: KASAN: vmalloc-out-of-bounds Write in pcpu_freelist_populate

From: Dmitry Vyukov <dvyukov@google.com>
To: syzbot <syzbot+942085bfb8f7a276af1c@syzkaller.appspotmail.com>,
	guro@fb.com, Eric Dumazet <edumazet@google.com>
Cc: andrii@kernel.org, Alexei Starovoitov <ast@kernel.org>,
	bpf <bpf@vger.kernel.org>, Daniel Borkmann <daniel@iogearbox.net>,
	John Fastabend <john.fastabend@gmail.com>,
	Martin KaFai Lau <kafai@fb.com>, KP Singh <kpsingh@chromium.org>,
	LKML <linux-kernel@vger.kernel.org>,
	netdev <netdev@vger.kernel.org>, Song Liu <songliubraving@fb.com>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
	Yonghong Song <yhs@fb.com>
Subject: Re: KASAN: vmalloc-out-of-bounds Write in pcpu_freelist_populate
Date: Tue, 8 Dec 2020 08:24:55 +0100	[thread overview]
Message-ID: <CACT4Y+bXh8=jKY=Fe2ykgk=h79pMpcTtxzOyWigUCws0bv_g6Q@mail.gmail.com> (raw)
In-Reply-To: <000000000000caabb705b5e550aa@google.com>

On Mon, Dec 7, 2020 at 9:03 PM syzbot
<syzbot+942085bfb8f7a276af1c@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    34da8721 selftests/bpf: Test bpf_sk_storage_get in tcp ite..
> git tree:       bpf-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=10c3b837500000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3cb098ab0334059f
> dashboard link: https://syzkaller.appspot.com/bug?extid=942085bfb8f7a276af1c
> compiler:       gcc (GCC) 10.1.0-syz 20200507
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+942085bfb8f7a276af1c@syzkaller.appspotmail.com

I assume this is also

#syz fix: bpf: Avoid overflows involving hash elem_size


> ==================================================================
> BUG: KASAN: vmalloc-out-of-bounds in pcpu_freelist_push_node kernel/bpf/percpu_freelist.c:33 [inline]
> BUG: KASAN: vmalloc-out-of-bounds in pcpu_freelist_populate+0x1fe/0x260 kernel/bpf/percpu_freelist.c:114
> Write of size 8 at addr ffffc90119e78020 by task syz-executor.4/27988
>
> CPU: 1 PID: 27988 Comm: syz-executor.4 Not tainted 5.10.0-rc6-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x107/0x163 lib/dump_stack.c:118
>  print_address_description.constprop.0.cold+0x5/0x4c8 mm/kasan/report.c:385
>  __kasan_report mm/kasan/report.c:545 [inline]
>  kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562
>  pcpu_freelist_push_node kernel/bpf/percpu_freelist.c:33 [inline]
>  pcpu_freelist_populate+0x1fe/0x260 kernel/bpf/percpu_freelist.c:114
>  prealloc_init kernel/bpf/hashtab.c:323 [inline]
>  htab_map_alloc+0x981/0x1230 kernel/bpf/hashtab.c:507
>  find_and_alloc_map kernel/bpf/syscall.c:123 [inline]
>  map_create kernel/bpf/syscall.c:829 [inline]
>  __do_sys_bpf+0xa81/0x5170 kernel/bpf/syscall.c:4374
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x45e0f9
> Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f679c7a7c68 EFLAGS: 00000246
>  ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045e0f9
> RDX: 0000000000000040 RSI: 0000000020000040 RDI: 0000000000000000
> RBP: 000000000119c068 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000119c034
> R13: 00007fffd601c75f R14: 00007f679c7a89c0 R15: 000000000119c034
>
>
> Memory state around the buggy address:
>  ffffc90119e77f00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>  ffffc90119e77f80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
> >ffffc90119e78000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>                                ^
>  ffffc90119e78080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>  ffffc90119e78100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
> ==================================================================
>
>
> ---
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>
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