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[73.241.150.58]) by smtp.gmail.com with ESMTPSA id o16sm21440047pfu.188.2020.08.03.09.41.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 03 Aug 2020 09:41:16 -0700 (PDT) Subject: Re: KMSAN: uninit-value in caif_seqpkt_sendmsg To: syzbot , alexios.zavras@intel.com, allison@lohutok.net, davem@davemloft.net, edumazet@google.com, glider@google.com, gregkh@linuxfoundation.org, kuba@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, swinslow@gmail.com, syzkaller-bugs@googlegroups.com, tglx@linutronix.de References: <0000000000007ab98a05abfbb9a7@google.com> From: Eric Dumazet Message-ID: <2d5e9990-a976-743d-8717-1193a7a4a498@gmail.com> Date: Mon, 3 Aug 2020 09:41:14 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <0000000000007ab98a05abfbb9a7@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/3/20 9:35 AM, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 8bbbc5cf kmsan: don't compile memmove > git tree: https://github.com/google/kmsan.git master > console output: https://syzkaller.appspot.com/x/log.txt?x=11fbfe09e00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=cd0e9a6b0e555cc3 > dashboard link: https://syzkaller.appspot.com/bug?extid=09a5d591c1f98cf5efcb > compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81) > userspace arch: i386 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=150ef74ee00000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=170e2109e00000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+09a5d591c1f98cf5efcb@syzkaller.appspotmail.com > > ===================================================== > BUG: KMSAN: uninit-value in caif_seqpkt_sendmsg+0x693/0xf60 net/caif/caif_socket.c:542 > CPU: 1 PID: 11244 Comm: syz-executor620 Not tainted 5.6.0-rc2-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+0x1c9/0x220 lib/dump_stack.c:118 > kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118 > __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215 > caif_seqpkt_sendmsg+0x693/0xf60 net/caif/caif_socket.c:542 > sock_sendmsg_nosec net/socket.c:652 [inline] > sock_sendmsg net/socket.c:672 [inline] > ____sys_sendmsg+0x12b6/0x1350 net/socket.c:2343 > ___sys_sendmsg net/socket.c:2397 [inline] > __sys_sendmmsg+0x808/0xc90 net/socket.c:2480 > __compat_sys_sendmmsg net/compat.c:656 [inline] > __do_compat_sys_sendmmsg net/compat.c:663 [inline] > __se_compat_sys_sendmmsg net/compat.c:660 [inline] > __ia32_compat_sys_sendmmsg+0x127/0x180 net/compat.c:660 > do_syscall_32_irqs_on arch/x86/entry/common.c:339 [inline] > do_fast_syscall_32+0x3c7/0x6e0 arch/x86/entry/common.c:410 > entry_SYSENTER_compat+0x68/0x77 arch/x86/entry/entry_64_compat.S:139 > RIP: 0023:0xf7f79d99 > Code: 90 e8 0b 00 00 00 f3 90 0f ae e8 eb f9 8d 74 26 00 89 3c 24 c3 90 90 90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90 > RSP: 002b:00000000ffbf4d6c EFLAGS: 00000292 ORIG_RAX: 0000000000000159 > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000020007600 > RDX: 0000000000000001 RSI: 0000000000000000 RDI: 00000000080bb508 > RBP: 0000000000000012 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 > > Local variable ----iovstack.i@__sys_sendmmsg created at: > ___sys_sendmsg net/socket.c:2388 [inline] > __sys_sendmmsg+0x6db/0xc90 net/socket.c:2480 > ___sys_sendmsg net/socket.c:2388 [inline] > __sys_sendmmsg+0x6db/0xc90 net/socket.c:2480 > ===================================================== > > > --- > This report 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 syzkaller@googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > syzbot can test patches for this issue, for details see: > https://goo.gl/tpsmEJ#testing-patches > It is not clear why this code tests iov_base instead of len. diff --git a/net/caif/caif_socket.c b/net/caif/caif_socket.c index 3ad0a1df6712834a7f70b21a78173a02c7cba897..e4540023a9404d44089ff11b8b912fa23d8de69f 100644 --- a/net/caif/caif_socket.c +++ b/net/caif/caif_socket.c @@ -539,7 +539,7 @@ static int caif_seqpkt_sendmsg(struct socket *sock, struct msghdr *msg, goto err; ret = -EINVAL; - if (unlikely(msg->msg_iter.iov->iov_base == NULL)) + if (unlikely(!len)) goto err; noblock = msg->msg_flags & MSG_DONTWAIT;