From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gerb Stralko Subject: WARNING in iov_iter_revert Date: Wed, 30 May 2018 00:58:36 -0400 (EDT) Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII To: aviadye@mellanox.com, davejwatson@fb.com, davem@davemloft.net, ilyal@mellanox.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Hello, I'm in the process of fixing this bug (https://syzkaller.appspot.com/bug?id=1339e0a805a4ddb11eaee6fb6b1bc905493ded77) However, there are a couple things I'm trying to wrap my head around to understand and fix this issue properly. I'm using the C reproducer from syzkaller[1] to trigger this issue which has been a huge help in learning the Linux kernel. First in tls_sw.c in tls_sw_sendmsg we having the following: `do_tcp_sendpages `tls_push_sg `tls_push_record returns -EPIPE (-32) because sk->sk_shudown is set. See do_tcp_sendpages in net/ipv4/tcp.c Do we need to check for -EPIPE before continuing in tls_sw.c after tls_push_record, for example: if (ret == -EAGAIN || ret == -EPIPE) ^^^^^^^^^^^^^^ goto send_end; If -EPIPE is valid and we don't need to check for that particular condition then calling iov_iter_revert might be wrong because of the second argument: ctx->sg_plaintext_size - orig_size Because that statement will evaluate to -1 because ctx->sg_plaintext_size has been set to zero from earlier when calling: `free_sg `tls_push_sg And orig_size is set to 1 from the beginning of the while loop: orig_size = ctx->sg_plaintext_size So calling iov_iter_revert with the second argument being -1 will trigger the warning in lib/iov_iter.c:iov_iter_revert: if (WARN_ON(unroll > MAX_RW_COUNT)) return; Am I correct in thinking EPIPE should be checked after returning from tls_push_record? Or do we need to do some sanity checks on sg_plaintext_size and orig_size before calling iov_iter_revert? Any help would be greatly appreciated. [1] https://syzkaller.appspot.com/text?tag=ReproC&x=141d5417800000 On Sunday, May 13, 2018 at 9:28:03 AM UTC-7, syzbot wrote: > > Hello, > > syzbot found the following crash on: > > HEAD commit: 427fbe89261d Merge branch 'next' of git://git.kernel.org/p.. > > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=16b33477800000 > kernel config: https://syzkaller.appspot.com/x/.config?x=fcce42b221691ff9 > dashboard link: > https://syzkaller.appspot.com/bug?extid=c226690f7b3126c5ee04 > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=144f1997800000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=141d5417800000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+c22669...@syzkaller.appspotmail.com > > random: sshd: uninitialized urandom read (32 bytes read) > random: sshd: uninitialized urandom read (32 bytes read) > random: sshd: uninitialized urandom read (32 bytes read) > random: sshd: uninitialized urandom read (32 bytes read) > random: sshd: uninitialized urandom read (32 bytes read) > WARNING: CPU: 1 PID: 4542 at lib/iov_iter.c:857 > iov_iter_revert+0x2ee/0xaa0 > lib/iov_iter.c:857 > Kernel panic - not syncing: panic_on_warn set ... > > CPU: 1 PID: 4542 Comm: syz-executor650 Not tainted 4.17.0-rc4+ #44 > 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+0x1b9/0x294 lib/dump_stack.c:113 > panic+0x22f/0x4de kernel/panic.c:184 > __warn.cold.8+0x163/0x1b3 kernel/panic.c:536 > report_bug+0x252/0x2d0 lib/bug.c:186 > fixup_bug arch/x86/kernel/traps.c:178 [inline] > do_error_trap+0x1de/0x490 arch/x86/kernel/traps.c:296 > do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315 > invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:992 > RIP: 0010:iov_iter_revert+0x2ee/0xaa0 lib/iov_iter.c:857 > RSP: 0018:ffff8801ad1bf700 EFLAGS: 00010293 > RAX: ffff8801ac55e6c0 RBX: 00000000ffffffff RCX: ffffffff835104a1 > RDX: 0000000000000000 RSI: ffffffff8351074e RDI: 0000000000000007 > RBP: ffff8801ad1bf760 R08: ffff8801ac55e6c0 R09: ffffed003b5e46c2 > R10: 0000000000000003 R11: 0000000000000001 R12: 0000000000000001 > R13: ffff8801ad1bfd60 R14: 0000000000000011 R15: ffff8801ae9ac040 > tls_sw_sendmsg+0xf1c/0x12d0 net/tls/tls_sw.c:448 > inet_sendmsg+0x19f/0x690 net/ipv4/af_inet.c:798 > sock_sendmsg_nosec net/socket.c:629 [inline] > sock_sendmsg+0xd5/0x120 net/socket.c:639 > ___sys_sendmsg+0x805/0x940 net/socket.c:2117 > __sys_sendmsg+0x115/0x270 net/socket.c:2155 > __do_sys_sendmsg net/socket.c:2164 [inline] > __se_sys_sendmsg net/socket.c:2162 [inline] > __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162 > do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x4403a9 > RSP: 002b:00007ffdcdfbd6c8 EFLAGS: 00000207 ORIG_RAX: 000000000000002e > RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004403a9 > RDX: 0000000000000000 RSI: 0000000020001340 RDI: 0000000000000003 > RBP: 00000000006ca018 R08: 000000000000001c R09: 000000000000001c > R10: 0000000020000180 R11: 0000000000000207 R12: 0000000000401cd0 > R13: 0000000000401d60 R14: 0000000000000000 R15: 0000000000000000 > Dumping ftrace buffer: > (ftrace buffer empty) > Kernel Offset: disabled > Rebooting in 86400 seconds.. > > > --- > This bug is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzk...@googlegroups.com . > > > syzbot will keep track of this bug report. See: > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with > syzbot. > syzbot can test patches for this bug, for details see: > https://goo.gl/tpsmEJ#testing-patches >