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Sat, 12 Sep 2020 23:20:56 -0700 (PDT) Received: from [192.168.0.104] ([49.207.209.61]) by smtp.gmail.com with ESMTPSA id x9sm7031293pfj.96.2020.09.12.23.20.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 12 Sep 2020 23:20:56 -0700 (PDT) To: Greg KH References: <20200913055639.15639-1-anant.thazhemadam@gmail.com> <20200913061351.GA585618@kroah.com> From: Anant Thazhemadam Message-ID: <89526337-9657-8f4d-3022-9f2ad830fbe9@gmail.com> Date: Sun, 13 Sep 2020 11:50:52 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200913061351.GA585618@kroah.com> Content-Language: en-US Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Jakub Kicinski , syzbot+09a5d591c1f98cf5efcb@syzkaller.appspotmail.com, "David S. Miller" , linux-kernel-mentees@lists.linuxfoundation.org Subject: Re: [Linux-kernel-mentees] [PATCH] net: fix uninit value error in __sys_sendmmsg X-BeenThere: linux-kernel-mentees@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-kernel-mentees-bounces@lists.linuxfoundation.org Sender: "Linux-kernel-mentees" On 13/09/20 11:43 am, Greg KH wrote: > On Sun, Sep 13, 2020 at 11:26:39AM +0530, Anant Thazhemadam wrote: >> The crash report showed that there was a local variable; >> >> ----iovstack.i@__sys_sendmmsg created at: >> ___sys_sendmsg net/socket.c:2388 [inline] >> __sys_sendmmsg+0x6db/0xc90 net/socket.c:2480 >> >> that was left uninitialized. >> >> The contents of iovstack are of interest, since the respective pointer >> is passed down as an argument to sendmsg_copy_msghdr as well. >> Initializing this contents of this stack prevents this bug from happening. >> >> Since the memory that was initialized is freed at the end of the function >> call, memory leaks are not likely to be an issue. >> >> syzbot seems to have triggered this error by passing an array of 0's as >> a parameter while making the initial system call. >> >> Reported-by: syzbot+09a5d591c1f98cf5efcb@syzkaller.appspotmail.com >> Tested-by: syzbot+09a5d591c1f98cf5efcb@syzkaller.appspotmail.com >> Signed-off-by: Anant Thazhemadam >> --- >> net/socket.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/net/socket.c b/net/socket.c >> index 0c0144604f81..d74443dfd73b 100644 >> --- a/net/socket.c >> +++ b/net/socket.c >> @@ -2396,6 +2396,7 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg, >> { >> struct sockaddr_storage address; >> struct iovec iovstack[UIO_FASTIOV], *iov = iovstack; >> + memset(iov, 0, UIO_FASTIOV); >> ssize_t err; >> >> msg_sys->msg_name = &address; > I don't think you built this code change, otherwise you would have seen > that it adds a build warning to the system, right? > > :( My apologies. I think I ended up overlooking the build warning. Thank you for pointing that out. If everything else looks good, I'd be happy to send in a v2 that fixes this build warning. Thanks, Anant _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees