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net: socket: move check for forbid_cmsg_compat to __sys_...msg()
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The non-compat codepaths for sys_...msg() verify that MSG_CMSG_COMPAT
is not set. By moving this check to the __sys_...msg() functions
(and making it dependent on a static flag passed to this function), we
can call the __sys...msg() functions instead of the syscall functions
in all cases. __sys_recvmmsg() does not need this trickery, as the
check is handled within the do_sys_recvmmsg() function internal to
net/socket.c.

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/[email protected]

Cc: David S. Miller <[email protected]>
Cc: [email protected]
Signed-off-by: Dominik Brodowski <[email protected]>
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Dominik Brodowski committed Apr 2, 2018
1 parent 1255e26 commit e1834a3
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Showing 3 changed files with 37 additions and 22 deletions.
13 changes: 9 additions & 4 deletions include/linux/socket.h
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Original file line number Diff line number Diff line change
Expand Up @@ -346,13 +346,18 @@ 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 user_msghdr __user *msg, unsigned flags);
extern long __sys_sendmsg(int fd, struct user_msghdr __user *msg, unsigned flags);
/* The __sys_...msg variants allow MSG_CMSG_COMPAT iff
* forbid_cmsg_compat==false
*/
extern long __sys_recvmsg(int fd, struct user_msghdr __user *msg,
unsigned int flags, bool forbid_cmsg_compat);
extern long __sys_sendmsg(int fd, struct user_msghdr __user *msg,
unsigned int flags, bool forbid_cmsg_compat);
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,
unsigned int vlen, unsigned int flags);
unsigned int vlen, unsigned int flags,
bool forbid_cmsg_compat);

/* helpers which do the actual work for syscalls */
extern int __sys_recvfrom(int fd, void __user *ubuf, size_t size,
Expand Down
8 changes: 5 additions & 3 deletions net/compat.c
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Original file line number Diff line number Diff line change
Expand Up @@ -736,19 +736,21 @@ static unsigned char nas[21] = {

COMPAT_SYSCALL_DEFINE3(sendmsg, int, fd, struct compat_msghdr __user *, msg, unsigned int, flags)
{
return __sys_sendmsg(fd, (struct user_msghdr __user *)msg, flags | MSG_CMSG_COMPAT);
return __sys_sendmsg(fd, (struct user_msghdr __user *)msg,
flags | MSG_CMSG_COMPAT, false);
}

COMPAT_SYSCALL_DEFINE4(sendmmsg, int, fd, struct compat_mmsghdr __user *, mmsg,
unsigned int, vlen, unsigned int, flags)
{
return __sys_sendmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,
flags | MSG_CMSG_COMPAT);
flags | MSG_CMSG_COMPAT, false);
}

COMPAT_SYSCALL_DEFINE3(recvmsg, int, fd, struct compat_msghdr __user *, msg, unsigned int, flags)
{
return __sys_recvmsg(fd, (struct user_msghdr __user *)msg, flags | MSG_CMSG_COMPAT);
return __sys_recvmsg(fd, (struct user_msghdr __user *)msg,
flags | MSG_CMSG_COMPAT, false);
}

COMPAT_SYSCALL_DEFINE4(recv, int, fd, void __user *, buf, compat_size_t, len, unsigned int, flags)
Expand Down
38 changes: 23 additions & 15 deletions net/socket.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2137,12 +2137,16 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
* BSD sendmsg interface
*/

long __sys_sendmsg(int fd, struct user_msghdr __user *msg, unsigned flags)
long __sys_sendmsg(int fd, struct user_msghdr __user *msg, unsigned int flags,
bool forbid_cmsg_compat)
{
int fput_needed, err;
struct msghdr msg_sys;
struct socket *sock;

if (forbid_cmsg_compat && (flags & MSG_CMSG_COMPAT))
return -EINVAL;

sock = sockfd_lookup_light(fd, &err, &fput_needed);
if (!sock)
goto out;
Expand All @@ -2156,17 +2160,15 @@ long __sys_sendmsg(int fd, struct user_msghdr __user *msg, unsigned flags)

SYSCALL_DEFINE3(sendmsg, int, fd, struct user_msghdr __user *, msg, unsigned int, flags)
{
if (flags & MSG_CMSG_COMPAT)
return -EINVAL;
return __sys_sendmsg(fd, msg, flags);
return __sys_sendmsg(fd, msg, flags, true);
}

/*
* Linux sendmmsg interface
*/

int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
unsigned int flags)
unsigned int flags, bool forbid_cmsg_compat)
{
int fput_needed, err, datagrams;
struct socket *sock;
Expand All @@ -2176,6 +2178,9 @@ int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
struct used_address used_address;
unsigned int oflags = flags;

if (forbid_cmsg_compat && (flags & MSG_CMSG_COMPAT))
return -EINVAL;

if (vlen > UIO_MAXIOV)
vlen = UIO_MAXIOV;

Expand Down Expand Up @@ -2232,9 +2237,7 @@ int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
SYSCALL_DEFINE4(sendmmsg, int, fd, struct mmsghdr __user *, mmsg,
unsigned int, vlen, unsigned int, flags)
{
if (flags & MSG_CMSG_COMPAT)
return -EINVAL;
return __sys_sendmmsg(fd, mmsg, vlen, flags);
return __sys_sendmmsg(fd, mmsg, vlen, flags, true);
}

static int ___sys_recvmsg(struct socket *sock, struct user_msghdr __user *msg,
Expand Down Expand Up @@ -2307,12 +2310,16 @@ static int ___sys_recvmsg(struct socket *sock, struct user_msghdr __user *msg,
* BSD recvmsg interface
*/

long __sys_recvmsg(int fd, struct user_msghdr __user *msg, unsigned flags)
long __sys_recvmsg(int fd, struct user_msghdr __user *msg, unsigned int flags,
bool forbid_cmsg_compat)
{
int fput_needed, err;
struct msghdr msg_sys;
struct socket *sock;

if (forbid_cmsg_compat && (flags & MSG_CMSG_COMPAT))
return -EINVAL;

sock = sockfd_lookup_light(fd, &err, &fput_needed);
if (!sock)
goto out;
Expand All @@ -2327,9 +2334,7 @@ long __sys_recvmsg(int fd, struct user_msghdr __user *msg, unsigned flags)
SYSCALL_DEFINE3(recvmsg, int, fd, struct user_msghdr __user *, msg,
unsigned int, flags)
{
if (flags & MSG_CMSG_COMPAT)
return -EINVAL;
return __sys_recvmsg(fd, msg, flags);
return __sys_recvmsg(fd, msg, flags, true);
}

/*
Expand Down Expand Up @@ -2580,13 +2585,16 @@ SYSCALL_DEFINE2(socketcall, int, call, unsigned long __user *, args)
(int __user *)a[4]);
break;
case SYS_SENDMSG:
err = sys_sendmsg(a0, (struct user_msghdr __user *)a1, a[2]);
err = __sys_sendmsg(a0, (struct user_msghdr __user *)a1,
a[2], true);
break;
case SYS_SENDMMSG:
err = sys_sendmmsg(a0, (struct mmsghdr __user *)a1, a[2], a[3]);
err = __sys_sendmmsg(a0, (struct mmsghdr __user *)a1, a[2],
a[3], true);
break;
case SYS_RECVMSG:
err = sys_recvmsg(a0, (struct user_msghdr __user *)a1, a[2]);
err = __sys_recvmsg(a0, (struct user_msghdr __user *)a1,
a[2], true);
break;
case SYS_RECVMMSG:
err = do_sys_recvmmsg(a0, (struct mmsghdr __user *)a1, a[2],
Expand Down

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