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authorUlrich Drepper <drepper@redhat.com>2007-07-15 23:40:34 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-16 09:05:45 -0700
commit4a19542e5f694cd408a32c3d9dc593ba9366e2d7 (patch)
tree12f5fd603b516b4e24ec4850d5589273d24be569
parentf23513e8d96cf5e6cf8d2ff0cb5dd6bbc33995e4 (diff)
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O_CLOEXEC for SCM_RIGHTS
Part two in the O_CLOEXEC saga: adding support for file descriptors received through Unix domain sockets. The patch is once again pretty minimal, it introduces a new flag for recvmsg and passes it just like the existing MSG_CMSG_COMPAT flag. I think this bit is not used otherwise but the networking people will know better. This new flag is not recognized by recvfrom and recv. These functions cannot be used for that purpose and the asymmetry this introduces is not worse than the already existing MSG_CMSG_COMPAT situations. The patch must be applied on the patch which introduced O_CLOEXEC. It has to remove static from the new get_unused_fd_flags function but since scm.c cannot live in a module the function still hasn't to be exported. Here's a test program to make sure the code works. It's so much longer than the actual patch... #include <errno.h> #include <error.h> #include <fcntl.h> #include <stdio.h> #include <string.h> #include <unistd.h> #include <sys/socket.h> #include <sys/un.h> #ifndef O_CLOEXEC # define O_CLOEXEC 02000000 #endif #ifndef MSG_CMSG_CLOEXEC # define MSG_CMSG_CLOEXEC 0x40000000 #endif int main (int argc, char *argv[]) { if (argc > 1) { int fd = atol (argv[1]); printf ("child: fd = %d\n", fd); if (fcntl (fd, F_GETFD) == 0 || errno != EBADF) { puts ("file descriptor valid in child"); return 1; } return 0; } struct sockaddr_un sun; strcpy (sun.sun_path, "./testsocket"); sun.sun_family = AF_UNIX; char databuf[] = "hello"; struct iovec iov[1]; iov[0].iov_base = databuf; iov[0].iov_len = sizeof (databuf); union { struct cmsghdr hdr; char bytes[CMSG_SPACE (sizeof (int))]; } buf; struct msghdr msg = { .msg_iov = iov, .msg_iovlen = 1, .msg_control = buf.bytes, .msg_controllen = sizeof (buf) }; struct cmsghdr *cmsg = CMSG_FIRSTHDR (&msg); cmsg->cmsg_level = SOL_SOCKET; cmsg->cmsg_type = SCM_RIGHTS; cmsg->cmsg_len = CMSG_LEN (sizeof (int)); msg.msg_controllen = cmsg->cmsg_len; pid_t child = fork (); if (child == -1) error (1, errno, "fork"); if (child == 0) { int sock = socket (PF_UNIX, SOCK_STREAM, 0); if (sock < 0) error (1, errno, "socket"); if (bind (sock, (struct sockaddr *) &sun, sizeof (sun)) < 0) error (1, errno, "bind"); if (listen (sock, SOMAXCONN) < 0) error (1, errno, "listen"); int conn = accept (sock, NULL, NULL); if (conn == -1) error (1, errno, "accept"); *(int *) CMSG_DATA (cmsg) = sock; if (sendmsg (conn, &msg, MSG_NOSIGNAL) < 0) error (1, errno, "sendmsg"); return 0; } /* For a test suite this should be more robust like a barrier in shared memory. */ sleep (1); int sock = socket (PF_UNIX, SOCK_STREAM, 0); if (sock < 0) error (1, errno, "socket"); if (connect (sock, (struct sockaddr *) &sun, sizeof (sun)) < 0) error (1, errno, "connect"); unlink (sun.sun_path); *(int *) CMSG_DATA (cmsg) = -1; if (recvmsg (sock, &msg, MSG_CMSG_CLOEXEC) < 0) error (1, errno, "recvmsg"); int fd = *(int *) CMSG_DATA (cmsg); if (fd == -1) error (1, 0, "no descriptor received"); char fdname[20]; snprintf (fdname, sizeof (fdname), "%d", fd); execl ("/proc/self/exe", argv[0], fdname, NULL); puts ("execl failed"); return 1; } [akpm@linux-foundation.org: Fix fastcall inconsistency noted by Michael Buesch] [akpm@linux-foundation.org: build fix] Signed-off-by: Ulrich Drepper <drepper@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Michael Buesch <mb@bu3sch.de> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/open.c2
-rw-r--r--include/linux/file.h1
-rw-r--r--include/linux/socket.h3
-rw-r--r--net/compat.c3
-rw-r--r--net/core/scm.c3
-rw-r--r--net/socket.c4
6 files changed, 10 insertions, 6 deletions
diff --git a/fs/open.c b/fs/open.c
index e6991c1b587..be6a457f422 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -855,7 +855,7 @@ EXPORT_SYMBOL(dentry_open);
/*
* Find an empty file descriptor entry, and mark it busy.
*/
-static int get_unused_fd_flags(int flags)
+int get_unused_fd_flags(int flags)
{
struct files_struct * files = current->files;
int fd, error;
diff --git a/include/linux/file.h b/include/linux/file.h
index a59001e9ea5..0114fbc7806 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -73,6 +73,7 @@ extern struct file * FASTCALL(fget_light(unsigned int fd, int *fput_needed));
extern void FASTCALL(set_close_on_exec(unsigned int fd, int flag));
extern void put_filp(struct file *);
extern int get_unused_fd(void);
+extern int get_unused_fd_flags(int flags);
extern void FASTCALL(put_unused_fd(unsigned int fd));
struct kmem_cache;
diff --git a/include/linux/socket.h b/include/linux/socket.h
index fe195c97a89..f852e1afd65 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -253,6 +253,9 @@ struct ucred {
#define MSG_EOF MSG_FIN
+#define MSG_CMSG_CLOEXEC 0x40000000 /* Set close_on_exit for file
+ descriptor received through
+ SCM_RIGHTS */
#if defined(CONFIG_COMPAT)
#define MSG_CMSG_COMPAT 0x80000000 /* This message needs 32 bit fixups */
#else
diff --git a/net/compat.c b/net/compat.c
index 9a0f5f2b90c..d74d82155d7 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -276,7 +276,8 @@ void scm_detach_fds_compat(struct msghdr *kmsg, struct scm_cookie *scm)
err = security_file_receive(fp[i]);
if (err)
break;
- err = get_unused_fd();
+ err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & kmsg->msg_flags
+ ? O_CLOEXEC : 0);
if (err < 0)
break;
new_fd = err;
diff --git a/net/core/scm.c b/net/core/scm.c
index 292ad8d5ad7..44c4ec2c876 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -228,7 +228,8 @@ void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
err = security_file_receive(fp[i]);
if (err)
break;
- err = get_unused_fd();
+ err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
+ ? O_CLOEXEC : 0);
if (err < 0)
break;
new_fd = err;
diff --git a/net/socket.c b/net/socket.c
index f4530196a70..b7111425004 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1939,9 +1939,7 @@ asmlinkage long sys_recvmsg(int fd, struct msghdr __user *msg,
total_len = err;
cmsg_ptr = (unsigned long)msg_sys.msg_control;
- msg_sys.msg_flags = 0;
- if (MSG_CMSG_COMPAT & flags)
- msg_sys.msg_flags = MSG_CMSG_COMPAT;
+ msg_sys.msg_flags = flags & (MSG_CMSG_CLOEXEC|MSG_CMSG_COMPAT);
if (sock->file->f_flags & O_NONBLOCK)
flags |= MSG_DONTWAIT;