From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Fastabend Subject: Re: WARNING in strp_data_ready Date: Mon, 30 Oct 2017 14:44:06 -0700 Message-ID: References: <001a11421c7436e541055c4c7cf0@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: "netdev@vger.kernel.org" To: syzbot , davem@davemloft.net, ebiggers@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com, tom@quantonium.net, xiyou.wangcong@gmail.com Return-path: In-Reply-To: <001a11421c7436e541055c4c7cf0@google.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 10/24/2017 08:20 AM, syzbot wrote: > Hello, > > syzkaller hit the following crash on 73d3393ada4f70fa3df5639c8d438f2f034c0ecb > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master > compiler: gcc (GCC) 7.1.1 20170620 > .config is attached > Raw console output is attached. > C reproducer is attached > syzkaller reproducer is attached. See https://goo.gl/kgGztJ > for information about syzkaller reproducers > > > WARNING: CPU: 0 PID: 2996 at ./include/net/sock.h:1505 sock_owned_by_me include/net/sock.h:1505 [inline] > WARNING: CPU: 0 PID: 2996 at ./include/net/sock.h:1505 sock_owned_by_user include/net/sock.h:1511 [inline] > WARNING: CPU: 0 PID: 2996 at ./include/net/sock.h:1505 strp_data_ready+0x2b7/0x390 net/strparser/strparser.c:404 > Kernel panic - not syncing: panic_on_warn set ... > > CPU: 0 PID: 2996 Comm: syzkaller142210 Not tainted 4.14.0-rc5+ #138 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > Call Trace: >   >  __dump_stack lib/dump_stack.c:16 [inline] >  dump_stack+0x194/0x257 lib/dump_stack.c:52 >  panic+0x1e4/0x417 kernel/panic.c:181 >  __warn+0x1c4/0x1d9 kernel/panic.c:542 >  report_bug+0x211/0x2d0 lib/bug.c:183 >  fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:178 >  do_trap_no_signal arch/x86/kernel/traps.c:212 [inline] >  do_trap+0x260/0x390 arch/x86/kernel/traps.c:261 >  do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:298 >  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:311 >  invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:905 > RIP: 0010:sock_owned_by_me include/net/sock.h:1505 [inline] > RIP: 0010:sock_owned_by_user include/net/sock.h:1511 [inline] > RIP: 0010:strp_data_ready+0x2b7/0x390 net/strparser/strparser.c:404 > RSP: 0018:ffff8801db206b18 EFLAGS: 00010206 > RAX: ffff8801d1e02080 RBX: ffff8801dad74c48 RCX: 0000000000000000 > RDX: 0000000000000100 RSI: ffff8801d29fa0a0 RDI: ffffffff85cbede0 > RBP: ffff8801db206b38 R08: 0000000000000005 R09: 1ffffffff0ce0bcd > R10: ffff8801db206a00 R11: dffffc0000000000 R12: ffff8801d29fa000 > R13: ffff8801dad74c50 R14: ffff8801d4350a92 R15: 0000000000000001 >  psock_data_ready+0x56/0x70 net/kcm/kcmsock.c:353 Looks like KCM is calling sk_data_ready() without first taking the sock lock. /* Called with lower sock held */ static void kcm_rcv_strparser(struct strparser *strp, struct sk_buff *skb) { [...] if (kcm_queue_rcv_skb(&kcm->sk, skb)) { In this case kcm->sk is not the same lock the comment is referring to. And kcm_queue_rcv_skb() will eventually call sk_data_ready(). @Tom, how about wrapping the sk_data_ready call in {lock|release}_sock? I don't have anything better in mind immediately. Thanks, John