From 6c5d0512a091480c9f981162227fdb1c9d70e555 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sat, 26 Jul 2008 13:38:19 -0400
Subject: [PATCH] get rid of corner case in dup3() entirely

Since Ulrich is OK with getting rid of dup3(fd, fd, flags) completely,
to hell the damn thing goes.  Corner case for dup2() is handled in
sys_dup2() (complete with -EBADF if dup2(fd, fd) is called with fd
that is not open), the rest is done in dup3().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/fcntl.c b/fs/fcntl.c
index ce12a68..3deec98 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -135,18 +135,12 @@ asmlinkage long sys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
 	if ((flags & ~O_CLOEXEC) != 0)
 		return -EINVAL;
 
+	if (unlikely(oldfd == newfd))
+		return -EINVAL;
+
 	spin_lock(&files->file_lock);
 	if (!(file = fcheck(oldfd)))
 		goto out_unlock;
-	err = newfd;
-	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;
 	get_file(file);			/* We are now finished with oldfd */
@@ -194,6 +188,14 @@ out_fput:
 
 asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
 {
+	if (unlikely(newfd == oldfd)) { /* corner case */
+		struct files_struct *files = current->files;
+		rcu_read_lock();
+		if (!fcheck_files(files, oldfd))
+			oldfd = -EBADF;
+		rcu_read_unlock();
+		return oldfd;
+	}
 	return sys_dup3(oldfd, newfd, 0);
 }
 
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