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SubjectRe: [PATCH] net: Unbreak compat_sys_{send,recv}msg
From
From: Andy Lutomirski <luto@amacapital.net>
Date: Wed, 5 Jun 2013 22:38:26 -0700

> I broke them in this commit:
>
> commit 1be374a0518a288147c6a7398792583200a67261
> Author: Andy Lutomirski <luto@amacapital.net>
> Date: Wed May 22 14:07:44 2013 -0700
>
> net: Block MSG_CMSG_COMPAT in send(m)msg and recv(m)msg
>
> This patch adds __sys_sendmsg and __sys_sendmsg as common helpers that accept
> MSG_CMSG_COMPAT and blocks MSG_CMSG_COMPAT at the syscall entrypoints. It
> also reverts some unnecessary checks in sys_socketcall.
>
> Apparently I was suffering from underscore blindness the first time around.
>
> Signed-off-by: Andy Lutomirski <luto@amacapital.net>

Eric, can you test this patch too?

Thanks.

> ---
>
> I've tested this a little, but I'm not sure I have a great test case.
>
> If the decision is that it's better to leave this for the 3.11, I can send
> a squashed version. Note that the oops that this fixes is only an oops if
> the other patches in the original series are applied.
>
> (FWIW, I wasn't sure how to submit this stuff in the first place. I submitted
> some kernel hardening patches for the x86 tree that converted an access_ok
> oddity in the net code into an actual oops. In a bit of looking, I couldn't
> find any failure mode other than a -EFAULT return without the other patches
> applied. This was clear in the patch series description but not in the
> change log message for the net part.)
>
> include/linux/socket.h | 3 +++
> net/compat.c | 13 +++++++--
> net/socket.c | 72 +++++++++++++++++++++++---------------------------
> 3 files changed, 47 insertions(+), 41 deletions(-)
>
> diff --git a/include/linux/socket.h b/include/linux/socket.h
> index 2b9f74b..e897bdc 100644
> --- a/include/linux/socket.h
> +++ b/include/linux/socket.h
> @@ -321,6 +321,9 @@ extern int put_cmsg(struct msghdr*, int level, int type, int len, void *data);
>
> struct timespec;
>
> +/* The __sys_...msg variants allow MSG_CMSG_COMPAT */
> +extern long __sys_recvmsg(int fd, struct msghdr __user *msg, unsigned flags);
> +extern long __sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags);
> extern int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
> unsigned int flags, struct timespec *timeout);
> extern int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg,
> diff --git a/net/compat.c b/net/compat.c
> index 79ae884..f0a1ba6 100644
> --- a/net/compat.c
> +++ b/net/compat.c
> @@ -734,19 +734,25 @@ static unsigned char nas[21] = {
>
> asmlinkage long compat_sys_sendmsg(int fd, struct compat_msghdr __user *msg, unsigned int flags)
> {
> - return sys_sendmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT);
> + if (flags & MSG_CMSG_COMPAT)
> + return -EINVAL;
> + return __sys_sendmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT);
> }
>
> asmlinkage long compat_sys_sendmmsg(int fd, struct compat_mmsghdr __user *mmsg,
> unsigned int vlen, unsigned int flags)
> {
> + if (flags & MSG_CMSG_COMPAT)
> + return -EINVAL;
> return __sys_sendmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,
> flags | MSG_CMSG_COMPAT);
> }
>
> asmlinkage long compat_sys_recvmsg(int fd, struct compat_msghdr __user *msg, unsigned int flags)
> {
> - return sys_recvmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT);
> + if (flags & MSG_CMSG_COMPAT)
> + return -EINVAL;
> + return __sys_recvmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT);
> }
>
> asmlinkage long compat_sys_recv(int fd, void __user *buf, size_t len, unsigned int flags)
> @@ -768,6 +774,9 @@ asmlinkage long compat_sys_recvmmsg(int fd, struct compat_mmsghdr __user *mmsg,
> int datagrams;
> struct timespec ktspec;
>
> + if (flags & MSG_CMSG_COMPAT)
> + return -EINVAL;
> +
> if (COMPAT_USE_64BIT_TIME)
> return __sys_recvmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,
> flags | MSG_CMSG_COMPAT,
> diff --git a/net/socket.c b/net/socket.c
> index 0e16888..e216502 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -1978,7 +1978,7 @@ struct used_address {
> unsigned int name_len;
> };
>
> -static int __sys_sendmsg(struct socket *sock, struct msghdr __user *msg,
> +static int ___sys_sendmsg(struct socket *sock, struct msghdr __user *msg,
> struct msghdr *msg_sys, unsigned int flags,
> struct used_address *used_address)
> {
> @@ -2093,26 +2093,30 @@ out:
> * BSD sendmsg interface
> */
>
> -SYSCALL_DEFINE3(sendmsg, int, fd, struct msghdr __user *, msg, unsigned int, flags)
> +long __sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags)
> {
> int fput_needed, err;
> struct msghdr msg_sys;
> struct socket *sock;
>
> - if (flags & MSG_CMSG_COMPAT)
> - return -EINVAL;
> -
> sock = sockfd_lookup_light(fd, &err, &fput_needed);
> if (!sock)
> goto out;
>
> - err = __sys_sendmsg(sock, msg, &msg_sys, flags, NULL);
> + err = ___sys_sendmsg(sock, msg, &msg_sys, flags, NULL);
>
> fput_light(sock->file, fput_needed);
> out:
> return err;
> }
>
> +SYSCALL_DEFINE3(sendmsg, int, fd, struct msghdr __user *, msg, unsigned int, flags)
> +{
> + if (flags & MSG_CMSG_COMPAT)
> + return -EINVAL;
> + return __sys_sendmsg(fd, msg, flags);
> +}
> +
> /*
> * Linux sendmmsg interface
> */
> @@ -2143,15 +2147,16 @@ int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
>
> while (datagrams < vlen) {
> if (MSG_CMSG_COMPAT & flags) {
> - err = __sys_sendmsg(sock, (struct msghdr __user *)compat_entry,
> - &msg_sys, flags, &used_address);
> + err = ___sys_sendmsg(sock, (struct msghdr __user *)compat_entry,
> + &msg_sys, flags, &used_address);
> if (err < 0)
> break;
> err = __put_user(err, &compat_entry->msg_len);
> ++compat_entry;
> } else {
> - err = __sys_sendmsg(sock, (struct msghdr __user *)entry,
> - &msg_sys, flags, &used_address);
> + err = ___sys_sendmsg(sock,
> + (struct msghdr __user *)entry,
> + &msg_sys, flags, &used_address);
> if (err < 0)
> break;
> err = put_user(err, &entry->msg_len);
> @@ -2180,7 +2185,7 @@ SYSCALL_DEFINE4(sendmmsg, int, fd, struct mmsghdr __user *, mmsg,
> return __sys_sendmmsg(fd, mmsg, vlen, flags);
> }
>
> -static int __sys_recvmsg(struct socket *sock, struct msghdr __user *msg,
> +static int ___sys_recvmsg(struct socket *sock, struct msghdr __user *msg,
> struct msghdr *msg_sys, unsigned int flags, int nosec)
> {
> struct compat_msghdr __user *msg_compat =
> @@ -2272,27 +2277,31 @@ out:
> * BSD recvmsg interface
> */
>
> -SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg,
> - unsigned int, flags)
> +long __sys_recvmsg(int fd, struct msghdr __user *msg, unsigned flags)
> {
> int fput_needed, err;
> struct msghdr msg_sys;
> struct socket *sock;
>
> - if (flags & MSG_CMSG_COMPAT)
> - return -EINVAL;
> -
> sock = sockfd_lookup_light(fd, &err, &fput_needed);
> if (!sock)
> goto out;
>
> - err = __sys_recvmsg(sock, msg, &msg_sys, flags, 0);
> + err = ___sys_recvmsg(sock, msg, &msg_sys, flags, 0);
>
> fput_light(sock->file, fput_needed);
> out:
> return err;
> }
>
> +SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg,
> + unsigned int, flags)
> +{
> + if (flags & MSG_CMSG_COMPAT)
> + return -EINVAL;
> + return __sys_recvmsg(fd, msg, flags);
> +}
> +
> /*
> * Linux recvmmsg interface
> */
> @@ -2330,17 +2339,18 @@ int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
> * No need to ask LSM for more than the first datagram.
> */
> if (MSG_CMSG_COMPAT & flags) {
> - err = __sys_recvmsg(sock, (struct msghdr __user *)compat_entry,
> - &msg_sys, flags & ~MSG_WAITFORONE,
> - datagrams);
> + err = ___sys_recvmsg(sock, (struct msghdr __user *)compat_entry,
> + &msg_sys, flags & ~MSG_WAITFORONE,
> + datagrams);
> if (err < 0)
> break;
> err = __put_user(err, &compat_entry->msg_len);
> ++compat_entry;
> } else {
> - err = __sys_recvmsg(sock, (struct msghdr __user *)entry,
> - &msg_sys, flags & ~MSG_WAITFORONE,
> - datagrams);
> + err = ___sys_recvmsg(sock,
> + (struct msghdr __user *)entry,
> + &msg_sys, flags & ~MSG_WAITFORONE,
> + datagrams);
> if (err < 0)
> break;
> err = put_user(err, &entry->msg_len);
> @@ -2525,31 +2535,15 @@ SYSCALL_DEFINE2(socketcall, int, call, unsigned long __user *, args)
> (int __user *)a[4]);
> break;
> case SYS_SENDMSG:
> - if (a[2] & MSG_CMSG_COMPAT) {
> - err = -EINVAL;
> - break;
> - }
> err = sys_sendmsg(a0, (struct msghdr __user *)a1, a[2]);
> break;
> case SYS_SENDMMSG:
> - if (a[3] & MSG_CMSG_COMPAT) {
> - err = -EINVAL;
> - break;
> - }
> err = sys_sendmmsg(a0, (struct mmsghdr __user *)a1, a[2], a[3]);
> break;
> case SYS_RECVMSG:
> - if (a[2] & MSG_CMSG_COMPAT) {
> - err = -EINVAL;
> - break;
> - }
> err = sys_recvmsg(a0, (struct msghdr __user *)a1, a[2]);
> break;
> case SYS_RECVMMSG:
> - if (a[3] & MSG_CMSG_COMPAT) {
> - err = -EINVAL;
> - break;
> - }
> err = sys_recvmmsg(a0, (struct mmsghdr __user *)a1, a[2], a[3],
> (struct timespec __user *)a[4]);
> break;
> --
> 1.8.1.4
>
> --
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