From: Eric Dumazet <eric.dumazet@gmail.com>
To: Yonghong Song <yhs@fb.com>,
ast@fb.com, daniel@iogearbox.net, netdev@vger.kernel.org
Cc: kernel-team@fb.com
Subject: Re: [PATCH bpf-next 1/2] bpf: implement MAP_GET_NEXT_KEY command for LPM_TRIE map
Date: Thu, 25 Jan 2018 20:47:33 -0800 [thread overview]
Message-ID: <1516942053.3715.58.camel@gmail.com> (raw)
In-Reply-To: <20180118230851.1533009-2-yhs@fb.com>
On Thu, 2018-01-18 at 15:08 -0800, Yonghong Song wrote:
> +find_leftmost:
> + /* Find the leftmost non-intermediate node, all intermediate nodes
> + * have exact two children, so this function will never return NULL.
> + */
syzbot [1] disagrees violently with this comment.
> + for (node = rcu_dereference(*root); node;) {
> + if (!(node->flags & LPM_TREE_NODE_FLAG_IM))
> + next_node = node;
> + node = rcu_dereference(node->child[0]);
> + }
> +do_copy:
> + next_key->prefixlen = next_node->prefixlen;
> + memcpy((void *)next_key + offsetof(struct bpf_lpm_trie_key, data),
> + next_node->data, trie->data_size);
[1]
syzbot hit the following crash on e9dcd80b9d77a92bfae6ce42a451f5c5fd318832
git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: https://syzkaller-buganizer.googleplex.com/text?tag=Config&id=b2216f04db2aa337e2bbf5ebd233919c3e2aa05f
compiler: gcc (GCC) 7.1.1 20170620
Unfortunately, I don't have any reproducer for this bug yet.
raw crash log: https://syzkaller-buganizer.googleplex.com/text?tag=CrashLog&id=4f78be02e2cd37040b8796322e02b147caae6024
dashboard link: https://syzkaller.appspot.com/bug?extid=148b56534d9269ab7433
See http://go/syzbot for details on how to handle this bug.
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 8033 Comm: syz-executor3 Not tainted 4.15.0-rc8+ #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:trie_get_next_key+0x3c2/0xf10 kernel/bpf/lpm_trie.c:682
RSP: 0018:ffff8801aa44f628 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff81829a9d
RDX: 0000000000000004 RSI: ffffc90003b7b000 RDI: 0000000000000020
RBP: ffff8801aa44f8b0 R08: ffffffff817e8f95 R09: 0000000000000002
R10: ffff8801aa44f790 R11: 0000000000000000 R12: 0000000000000000
R13: 1ffff10035489f01 R14: fffffffffffffff4 R15: 0000000000000000
FS: 00007fbb3b39b700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000002057a000 CR3: 00000001c26e4005 CR4: 00000000001606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
map_get_next_key kernel/bpf/syscall.c:842 [inline]
SYSC_bpf kernel/bpf/syscall.c:1881 [inline]
SyS_bpf+0x11b4/0x4860 kernel/bpf/syscall.c:1846
entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452f19
RSP: 002b:00007fbb3b39ac58 EFLAGS: 00000212 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452f19
RDX: 0000000000000018 RSI: 0000000020daf000 RDI: 0000000000000004
RBP: 000000000000003e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006ef670
R13: 00000000ffffffff R14: 00007fbb3b39b6d4 R15: 0000000000000000
Code: 19 d3 ff e8 81 98 ed ff 4d 85 e4 0f 85 30 ff ff ff e8 73 98 ed ff 49 8d 7f 20 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e f2 0a 00 00 48 8b b5 98 fd
RIP: trie_get_next_key+0x3c2/0xf10 kernel/bpf/lpm_trie.c:682 RSP: ffff8801aa44f628
---[ end trace b4eb675edf4c4059 ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..
next prev parent reply other threads:[~2018-01-26 4:47 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-18 23:08 [PATCH bpf-next 0/2] bpf: implement MAP_GET_NEXT_KEY command for LPM_TRIE map Yonghong Song
2018-01-18 23:08 ` [PATCH bpf-next 1/2] " Yonghong Song
2018-01-22 19:28 ` Eric Dumazet
2018-01-23 0:05 ` Yonghong Song
2018-01-26 4:47 ` Eric Dumazet [this message]
2018-01-26 16:50 ` Yonghong Song
2018-01-18 23:08 ` [PATCH bpf-next 2/2] tools/bpf: add a testcase for MAP_GET_NEXT_KEY command of " Yonghong Song
2018-01-20 1:07 ` [PATCH bpf-next 0/2] bpf: implement MAP_GET_NEXT_KEY command for " Daniel Borkmann
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