f23513e8d9
The problem is as follows: in multi-threaded code (or more correctly: all code using clone() with CLONE_FILES) we have a race when exec'ing. thread #1 thread #2 fd=open() fork + exec fcntl(fd,F_SETFD,FD_CLOEXEC) In some applications this can happen frequently. Take a web browser. One thread opens a file and another thread starts, say, an external PDF viewer. The result can even be a security issue if that open file descriptor refers to a sensitive file and the external program can somehow be tricked into using that descriptor. Just adding O_CLOEXEC support to open() doesn't solve the whole set of problems. There are other ways to create file descriptors (socket, epoll_create, Unix domain socket transfer, etc). These can and should be addressed separately though. open() is such an easy case that it makes not much sense putting the fix off. The test program: #include <errno.h> #include <fcntl.h> #include <stdio.h> #include <unistd.h> #ifndef O_CLOEXEC # define O_CLOEXEC 02000000 #endif int main (int argc, char *argv[]) { int fd; if (argc > 1) { 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; } fd = open ("/proc/self/exe", O_RDONLY | O_CLOEXEC); printf ("in parent: new fd = %d\n", fd); char buf[20]; snprintf (buf, sizeof (buf), "%d", fd); execl ("/proc/self/exe", argv[0], buf, NULL); puts ("execl failed"); return 1; } [kyle@parisc-linux.org: parisc fix] Signed-off-by: Ulrich Drepper <drepper@redhat.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Cc: Chris Zankel <chris@zankel.net> Signed-off-by: Kyle McMartin <kyle@parisc-linux.org> 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>
39 lines
1.2 KiB
C
39 lines
1.2 KiB
C
#ifndef _PARISC_FCNTL_H
|
|
#define _PARISC_FCNTL_H
|
|
|
|
/* open/fcntl - O_SYNC is only implemented on blocks devices and on files
|
|
located on an ext2 file system */
|
|
#define O_APPEND 000000010
|
|
#define O_BLKSEEK 000000100 /* HPUX only */
|
|
#define O_CREAT 000000400 /* not fcntl */
|
|
#define O_EXCL 000002000 /* not fcntl */
|
|
#define O_LARGEFILE 000004000
|
|
#define O_SYNC 000100000
|
|
#define O_NONBLOCK 000200004 /* HPUX has separate NDELAY & NONBLOCK */
|
|
#define O_NOCTTY 000400000 /* not fcntl */
|
|
#define O_DSYNC 001000000 /* HPUX only */
|
|
#define O_RSYNC 002000000 /* HPUX only */
|
|
#define O_NOATIME 004000000
|
|
#define O_CLOEXEC 010000000 /* set close_on_exec */
|
|
|
|
#define O_DIRECTORY 000010000 /* must be a directory */
|
|
#define O_NOFOLLOW 000000200 /* don't follow links */
|
|
#define O_INVISIBLE 004000000 /* invisible I/O, for DMAPI/XDSM */
|
|
|
|
#define F_GETLK64 8
|
|
#define F_SETLK64 9
|
|
#define F_SETLKW64 10
|
|
|
|
#define F_GETOWN 11 /* for sockets. */
|
|
#define F_SETOWN 12 /* for sockets. */
|
|
#define F_SETSIG 13 /* for sockets. */
|
|
#define F_GETSIG 14 /* for sockets. */
|
|
|
|
/* for posix fcntl() and lockf() */
|
|
#define F_RDLCK 01
|
|
#define F_WRLCK 02
|
|
#define F_UNLCK 03
|
|
|
|
#include <asm-generic/fcntl.h>
|
|
|
|
#endif
|