From mboxrd@z Thu Jan 1 00:00:00 1970 From: Junling Zheng Subject: [RFC] [PATCH] net: socket: Fix the wrong returns for recvmsg and sendmsg Date: Mon, 1 Jun 2015 09:28:00 +0000 Message-ID: <1433150880-9976-1-git-send-email-zhengjunling@huawei.com> Mime-Version: 1.0 Content-Type: text/plain Cc: , , , , , To: Return-path: Sender: stable-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Hi, Greg: We found that after v3.10.73, recvmsg might return -EFAULT while -EINVAL was expected. We tested it through the recvmsg01 testcase come from LTP testsuit. It set msg->msg_namelen to -1 and the recvmsg syscall returned errno 14, which is unexpected (errno 22 is expected): recvmsg01 4 TFAIL : invalid socket length ; returned -1 (expected -1), errno 14 (expected 22) Linux mainline has no this bug for commit 08adb7dab fixes it accidentally. However, it is too large and complex to be backported to LTS 3.10. So, I made the following patch to fix the above problem for LTS 3.10. Cheers, Junling ============ Commit 281c9c36 (net: compat: Update get_compat_msghdr() to match copy_msghdr_from_user() behaviour) made get_compat_msghdr() return error if msg_sys->msg_namelen was negative, which changed the behaviors of recvmsg and sendmsg syscall in a lib32 system: Before commit 281c9c36, get_compat_msghdr() wouldn't fail and it would return -EINVAL in move_addr_to_user() or somewhere if msg_sys->msg_namelen was invalid and then syscall returned -EINVAL, which is correct. And now, when msg_sys->msg_namelen is negative, get_compat_msghdr() will fail and wants to return -EINVAL, however, the outer syscall will return -EFAULT directly, which is unexpected. This patch gets the return value of get_compat_msghdr() as well as copy_msghdr_from_user(), then returns this expected value if get_compat_msghdr() fails. Fixes: 281c9c36 (net: compat: Update get_compat_msghdr() to match copy_msghdr_from_user() behaviour) Signed-off-by: Junling Zheng Signed-off-by: Hanbing Xu Cc: Li Zefan Cc: Al Viro Cc: David Miller --- net/socket.c | 24 ++++++++++-------------- 1 file changed, 10 insertions(+), 14 deletions(-) diff --git a/net/socket.c b/net/socket.c index fc90b4f..53b6e41 100644 --- a/net/socket.c +++ b/net/socket.c @@ -1988,14 +1988,12 @@ static int ___sys_sendmsg(struct socket *sock, struct msghdr __user *msg, int err, ctl_len, total_len; err = -EFAULT; - if (MSG_CMSG_COMPAT & flags) { - if (get_compat_msghdr(msg_sys, msg_compat)) - return -EFAULT; - } else { + if (MSG_CMSG_COMPAT & flags) + err = get_compat_msghdr(msg_sys, msg_compat); + else err = copy_msghdr_from_user(msg_sys, msg); - if (err) - return err; - } + if (err) + return err; if (msg_sys->msg_iovlen > UIO_FASTIOV) { err = -EMSGSIZE; @@ -2200,14 +2198,12 @@ static int ___sys_recvmsg(struct socket *sock, struct msghdr __user *msg, struct sockaddr __user *uaddr; int __user *uaddr_len; - if (MSG_CMSG_COMPAT & flags) { - if (get_compat_msghdr(msg_sys, msg_compat)) - return -EFAULT; - } else { + if (MSG_CMSG_COMPAT & flags) + err = get_compat_msghdr(msg_sys, msg_compat); + else err = copy_msghdr_from_user(msg_sys, msg); - if (err) - return err; - } + if (err) + return err; if (msg_sys->msg_iovlen > UIO_FASTIOV) { err = -EMSGSIZE; -- 1.8.3.4