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authorUlrich Drepper <drepper@redhat.com>2008-11-19 15:36:14 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2008-11-19 18:49:57 -0800
commitde11defebf00007677fb7ee91d9b089b78786fbb (patch)
tree8219faf1b7992be77a612e778c2573c55f56cf19 /net/socket.c
parentcf7ee554f3a324e98181b0ea249d9d5be3a0acb8 (diff)
reintroduce accept4
Introduce a new accept4() system call. The addition of this system call matches analogous changes in 2.6.27 (dup3(), evenfd2(), signalfd4(), inotify_init1(), epoll_create1(), pipe2()) which added new system calls that differed from analogous traditional system calls in adding a flags argument that can be used to access additional functionality. The accept4() system call is exactly the same as accept(), except that it adds a flags bit-mask argument. Two flags are initially implemented. (Most of the new system calls in 2.6.27 also had both of these flags.) SOCK_CLOEXEC causes the close-on-exec (FD_CLOEXEC) flag to be enabled for the new file descriptor returned by accept4(). This is a useful security feature to avoid leaking information in a multithreaded program where one thread is doing an accept() at the same time as another thread is doing a fork() plus exec(). More details here: http://udrepper.livejournal.com/20407.html "Secure File Descriptor Handling", Ulrich Drepper). The other flag is SOCK_NONBLOCK, which causes the O_NONBLOCK flag to be enabled on the new open file description created by accept4(). (This flag is merely a convenience, saving the use of additional calls fcntl(F_GETFL) and fcntl (F_SETFL) to achieve the same result. Here's a test program. Works on x86-32. Should work on x86-64, but I (mtk) don't have a system to hand to test with. It tests accept4() with each of the four possible combinations of SOCK_CLOEXEC and SOCK_NONBLOCK set/clear in 'flags', and verifies that the appropriate flags are set on the file descriptor/open file description returned by accept4(). I tested Ulrich's patch in this thread by applying against 2.6.28-rc2, and it passes according to my test program. /* test_accept4.c Copyright (C) 2008, Linux Foundation, written by Michael Kerrisk <mtk.manpages@gmail.com> Licensed under the GNU GPLv2 or later. */ #define _GNU_SOURCE #include <unistd.h> #include <sys/syscall.h> #include <sys/socket.h> #include <netinet/in.h> #include <stdlib.h> #include <fcntl.h> #include <stdio.h> #include <string.h> #define PORT_NUM 33333 #define die(msg) do { perror(msg); exit(EXIT_FAILURE); } while (0) /**********************************************************************/ /* The following is what we need until glibc gets a wrapper for accept4() */ /* Flags for socket(), socketpair(), accept4() */ #ifndef SOCK_CLOEXEC #define SOCK_CLOEXEC O_CLOEXEC #endif #ifndef SOCK_NONBLOCK #define SOCK_NONBLOCK O_NONBLOCK #endif #ifdef __x86_64__ #define SYS_accept4 288 #elif __i386__ #define USE_SOCKETCALL 1 #define SYS_ACCEPT4 18 #else #error "Sorry -- don't know the syscall # on this architecture" #endif static int accept4(int fd, struct sockaddr *sockaddr, socklen_t *addrlen, int flags) { printf("Calling accept4(): flags = %x", flags); if (flags != 0) { printf(" ("); if (flags & SOCK_CLOEXEC) printf("SOCK_CLOEXEC"); if ((flags & SOCK_CLOEXEC) && (flags & SOCK_NONBLOCK)) printf(" "); if (flags & SOCK_NONBLOCK) printf("SOCK_NONBLOCK"); printf(")"); } printf("\n"); #if USE_SOCKETCALL long args[6]; args[0] = fd; args[1] = (long) sockaddr; args[2] = (long) addrlen; args[3] = flags; return syscall(SYS_socketcall, SYS_ACCEPT4, args); #else return syscall(SYS_accept4, fd, sockaddr, addrlen, flags); #endif } /**********************************************************************/ static int do_test(int lfd, struct sockaddr_in *conn_addr, int closeonexec_flag, int nonblock_flag) { int connfd, acceptfd; int fdf, flf, fdf_pass, flf_pass; struct sockaddr_in claddr; socklen_t addrlen; printf("=======================================\n"); connfd = socket(AF_INET, SOCK_STREAM, 0); if (connfd == -1) die("socket"); if (connect(connfd, (struct sockaddr *) conn_addr, sizeof(struct sockaddr_in)) == -1) die("connect"); addrlen = sizeof(struct sockaddr_in); acceptfd = accept4(lfd, (struct sockaddr *) &claddr, &addrlen, closeonexec_flag | nonblock_flag); if (acceptfd == -1) { perror("accept4()"); close(connfd); return 0; } fdf = fcntl(acceptfd, F_GETFD); if (fdf == -1) die("fcntl:F_GETFD"); fdf_pass = ((fdf & FD_CLOEXEC) != 0) == ((closeonexec_flag & SOCK_CLOEXEC) != 0); printf("Close-on-exec flag is %sset (%s); ", (fdf & FD_CLOEXEC) ? "" : "not ", fdf_pass ? "OK" : "failed"); flf = fcntl(acceptfd, F_GETFL); if (flf == -1) die("fcntl:F_GETFD"); flf_pass = ((flf & O_NONBLOCK) != 0) == ((nonblock_flag & SOCK_NONBLOCK) !=0); printf("nonblock flag is %sset (%s)\n", (flf & O_NONBLOCK) ? "" : "not ", flf_pass ? "OK" : "failed"); close(acceptfd); close(connfd); printf("Test result: %s\n", (fdf_pass && flf_pass) ? "PASS" : "FAIL"); return fdf_pass && flf_pass; } static int create_listening_socket(int port_num) { struct sockaddr_in svaddr; int lfd; int optval; memset(&svaddr, 0, sizeof(struct sockaddr_in)); svaddr.sin_family = AF_INET; svaddr.sin_addr.s_addr = htonl(INADDR_ANY); svaddr.sin_port = htons(port_num); lfd = socket(AF_INET, SOCK_STREAM, 0); if (lfd == -1) die("socket"); optval = 1; if (setsockopt(lfd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval)) == -1) die("setsockopt"); if (bind(lfd, (struct sockaddr *) &svaddr, sizeof(struct sockaddr_in)) == -1) die("bind"); if (listen(lfd, 5) == -1) die("listen"); return lfd; } int main(int argc, char *argv[]) { struct sockaddr_in conn_addr; int lfd; int port_num; int passed; passed = 1; port_num = (argc > 1) ? atoi(argv[1]) : PORT_NUM; memset(&conn_addr, 0, sizeof(struct sockaddr_in)); conn_addr.sin_family = AF_INET; conn_addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK); conn_addr.sin_port = htons(port_num); lfd = create_listening_socket(port_num); if (!do_test(lfd, &conn_addr, 0, 0)) passed = 0; if (!do_test(lfd, &conn_addr, SOCK_CLOEXEC, 0)) passed = 0; if (!do_test(lfd, &conn_addr, 0, SOCK_NONBLOCK)) passed = 0; if (!do_test(lfd, &conn_addr, SOCK_CLOEXEC, SOCK_NONBLOCK)) passed = 0; close(lfd); exit(passed ? EXIT_SUCCESS : EXIT_FAILURE); } [mtk.manpages@gmail.com: rewrote changelog, updated test program] Signed-off-by: Ulrich Drepper <drepper@redhat.com> Tested-by: Michael Kerrisk <mtk.manpages@gmail.com> Acked-by: Michael Kerrisk <mtk.manpages@gmail.com> Cc: <linux-api@vger.kernel.org> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'net/socket.c')
-rw-r--r--net/socket.c80
1 files changed, 10 insertions, 70 deletions
diff --git a/net/socket.c b/net/socket.c
index 57550c3bcab..92764d83689 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1426,8 +1426,8 @@ asmlinkage long sys_listen(int fd, int backlog)
* clean when we restucture accept also.
*/
-long do_accept(int fd, struct sockaddr __user *upeer_sockaddr,
- int __user *upeer_addrlen, int flags)
+asmlinkage long sys_accept4(int fd, struct sockaddr __user *upeer_sockaddr,
+ int __user *upeer_addrlen, int flags)
{
struct socket *sock, *newsock;
struct file *newfile;
@@ -1510,66 +1510,10 @@ out_fd:
goto out_put;
}
-#if 0
-#ifdef HAVE_SET_RESTORE_SIGMASK
-asmlinkage long sys_paccept(int fd, struct sockaddr __user *upeer_sockaddr,
- int __user *upeer_addrlen,
- const sigset_t __user *sigmask,
- size_t sigsetsize, int flags)
-{
- sigset_t ksigmask, sigsaved;
- int ret;
-
- if (sigmask) {
- /* XXX: Don't preclude handling different sized sigset_t's. */
- if (sigsetsize != sizeof(sigset_t))
- return -EINVAL;
- if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
- return -EFAULT;
-
- sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
- sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
- }
-
- ret = do_accept(fd, upeer_sockaddr, upeer_addrlen, flags);
-
- if (ret < 0 && signal_pending(current)) {
- /*
- * Don't restore the signal mask yet. Let do_signal() deliver
- * the signal on the way back to userspace, before the signal
- * mask is restored.
- */
- if (sigmask) {
- memcpy(&current->saved_sigmask, &sigsaved,
- sizeof(sigsaved));
- set_restore_sigmask();
- }
- } else if (sigmask)
- sigprocmask(SIG_SETMASK, &sigsaved, NULL);
-
- return ret;
-}
-#else
-asmlinkage long sys_paccept(int fd, struct sockaddr __user *upeer_sockaddr,
- int __user *upeer_addrlen,
- const sigset_t __user *sigmask,
- size_t sigsetsize, int flags)
-{
- /* The platform does not support restoring the signal mask in the
- * return path. So we do not allow using paccept() with a signal
- * mask. */
- if (sigmask)
- return -EINVAL;
-
- return do_accept(fd, upeer_sockaddr, upeer_addrlen, flags);
-}
-#endif
-#endif
-
asmlinkage long sys_accept(int fd, struct sockaddr __user *upeer_sockaddr,
int __user *upeer_addrlen)
{
- return do_accept(fd, upeer_sockaddr, upeer_addrlen, 0);
+ return sys_accept4(fd, upeer_sockaddr, upeer_addrlen, 0);
}
/*
@@ -2096,7 +2040,7 @@ static const unsigned char nargs[19]={
AL(0),AL(3),AL(3),AL(3),AL(2),AL(3),
AL(3),AL(3),AL(4),AL(4),AL(4),AL(6),
AL(6),AL(2),AL(5),AL(5),AL(3),AL(3),
- AL(6)
+ AL(4)
};
#undef AL
@@ -2115,7 +2059,7 @@ asmlinkage long sys_socketcall(int call, unsigned long __user *args)
unsigned long a0, a1;
int err;
- if (call < 1 || call > SYS_PACCEPT)
+ if (call < 1 || call > SYS_ACCEPT4)
return -EINVAL;
/* copy_from_user should be SMP safe. */
@@ -2143,9 +2087,8 @@ asmlinkage long sys_socketcall(int call, unsigned long __user *args)
err = sys_listen(a0, a1);
break;
case SYS_ACCEPT:
- err =
- do_accept(a0, (struct sockaddr __user *)a1,
- (int __user *)a[2], 0);
+ err = sys_accept4(a0, (struct sockaddr __user *)a1,
+ (int __user *)a[2], 0);
break;
case SYS_GETSOCKNAME:
err =
@@ -2192,12 +2135,9 @@ asmlinkage long sys_socketcall(int call, unsigned long __user *args)
case SYS_RECVMSG:
err = sys_recvmsg(a0, (struct msghdr __user *)a1, a[2]);
break;
- case SYS_PACCEPT:
- err =
- sys_paccept(a0, (struct sockaddr __user *)a1,
- (int __user *)a[2],
- (const sigset_t __user *) a[3],
- a[4], a[5]);
+ case SYS_ACCEPT4:
+ err = sys_accept4(a0, (struct sockaddr __user *)a1,
+ (int __user *)a[2], a[3]);
break;
default:
err = -EINVAL;