[PATCH] dup3 fix

Al Viro notice one cornercase that the new dup3() code. The dup2() function, as a special case, handles dup-ing to the same file descriptor. In this case the current dup3() code does nothing at all. I.e., it ingnores the flags parameter. This shouldn't happen, the close-on-exec flag should be set if requested. In case the O_CLOEXEC bit in the flags parameter is not set the dup3() function should behave in this respect identical to dup2(). This means dup3(fd, fd, 0) should not actively reset the c-o-e flag. The patch below implements this minor change. [AV: credits to Artur Grabowski for bringing that up as potential subtle point in dup2() behaviour] Signed-off-by: Ulrich Drepper <[email protected]> Signed-off-by: Al Viro <[email protected]>
chewitt · Jul 27, 2008 · 3c33393 · 3c33393
1 parent 58ec42b
commit 3c33393
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/fs/fcntl.c b/fs/fcntl.c
@@ -139,8 +139,13 @@ asmlinkage long sys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
 	if (!(file = fcheck(oldfd)))
 		goto out_unlock;
 	err = newfd;
-	if (newfd == oldfd)
+	if (unlikely(newfd == oldfd)) {
+		if (flags & O_CLOEXEC) {
+			fdt = files_fdtable(files);
+			FD_SET(newfd, fdt->close_on_exec);
+		}
 		goto out_unlock;
+	}
 	err = -EBADF;
 	if (newfd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
 		goto out_unlock;