[PATCH 4/4] net: Add SOCK_CLOFORK

Nate Karstens
2020-04-20T07:16:25Z

Implements a new socket flag that automatically sets the
close-on-fork flag for sockets created using socket(2),
socketpair(2), and accept4(2).

Signed-off-by: Nate Karstens <nate.karstens@garmin.com>
---
include/linux/net.h | 3 ++-
net/socket.c | 14 ++++++++------
2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/include/linux/net.h b/include/linux/net.h
index 6451425e828f..57663c9dc8c4 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -17,7 +17,7 @@
#include <linux/stringify.h>
#include <linux/random.h>
#include <linux/wait.h>
-#include <linux/fcntl.h> /* For O_CLOEXEC and O_NONBLOCK */
+#include <linux/fcntl.h> /* For O_CLOEXEC, O_CLOFORK, and O_NONBLOCK */
#include <linux/rcupdate.h>
#include <linux/once.h>
#include <linux/fs.h>
@@ -73,6 +73,7 @@ enum sock_type {

/* Flags for socket, socketpair, accept4 */
#define SOCK_CLOEXEC O_CLOEXEC
+#define SOCK_CLOFORK O_CLOFORK
#ifndef SOCK_NONBLOCK
#define SOCK_NONBLOCK O_NONBLOCK
#endif
diff --git a/net/socket.c b/net/socket.c
index 2eecf1517f76..ba6e971c7e78 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1511,12 +1511,14 @@ int __sys_socket(int family, int type, int protocol)

/* Check the SOCK_* constants for consistency. */
BUILD_BUG_ON(SOCK_CLOEXEC != O_CLOEXEC);
+ BUILD_BUG_ON(SOCK_CLOFORK != O_CLOFORK);
BUILD_BUG_ON((SOCK_MAX | SOCK_TYPE_MASK) != SOCK_TYPE_MASK);
BUILD_BUG_ON(SOCK_CLOEXEC & SOCK_TYPE_MASK);
+ BUILD_BUG_ON(SOCK_CLOFORK & SOCK_TYPE_MASK);
BUILD_BUG_ON(SOCK_NONBLOCK & SOCK_TYPE_MASK);

flags = type & ~SOCK_TYPE_MASK;
- if (flags & ~(SOCK_CLOEXEC | SOCK_NONBLOCK))
+ if (flags & ~(SOCK_CLOEXEC | SOCK_CLOFORK | SOCK_NONBLOCK))
return -EINVAL;
type &= SOCK_TYPE_MASK;

@@ -1527,7 +1529,7 @@ int __sys_socket(int family, int type, int protocol)
if (retval < 0)
return retval;

- return sock_map_fd(sock, flags & (O_CLOEXEC | O_NONBLOCK));
+ return sock_map_fd(sock, flags & (O_CLOEXEC | O_CLOFORK | O_NONBLOCK));
}

SYSCALL_DEFINE3(socket, int, family, int, type, int, protocol)
@@ -1547,7 +1549,7 @@ int __sys_socketpair(int family, int type, int protocol, int __user *usockvec)
int flags;

flags = type & ~SOCK_TYPE_MASK;
- if (flags & ~(SOCK_CLOEXEC | SOCK_NONBLOCK))
+ if (flags & ~(SOCK_CLOEXEC | SOCK_CLOFORK | SOCK_NONBLOCK))
return -EINVAL;
type &= SOCK_TYPE_MASK;

@@ -1715,7 +1717,7 @@ int __sys_accept4_file(struct file *file, unsigned file_flags,
int err, len, newfd;
struct sockaddr_storage address;

- if (flags & ~(SOCK_CLOEXEC | SOCK_NONBLOCK))
+ if (flags & ~(SOCK_CLOEXEC | SOCK_CLOFORK | SOCK_NONBLOCK))
return -EINVAL;

if (SOCK_NONBLOCK != O_NONBLOCK && (flags & SOCK_NONBLOCK))
@@ -3628,8 +3630,8 @@ EXPORT_SYMBOL(kernel_listen);
* @newsock: new connected socket
* @flags: flags
*
- * @flags must be SOCK_CLOEXEC, SOCK_NONBLOCK or 0.
- * If it fails, @newsock is guaranteed to be %NULL.
+ * @flags must be SOCK_CLOEXEC, SOCK_CLOFORK, SOCK_NONBLOCK,
+ * or 0. If it fails, @newsock is guaranteed to be %NULL.
* Returns 0 or an error.
*/

--
2.26.1