[PATCH 41/73] union-mount: Temporarily disable some syscalls [ver #2]

[David Howells]

From: Valerie Aurora <vaurora@xxxxxxxxxx>

After some of the following patches in this series, a few system calls
will crash the kernel if called on union-mounted file systems.
Temporarily disable rename(), unlink(), and rmdir() on unioned file
systems until they are correctly implemented by later patches.

Original-author: Valerie Aurora <vaurora@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---

 fs/namei.c |   17 +++++++++++++++++
 1 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 991a32c..f53c0bc 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -38,6 +38,7 @@
 
 #include "internal.h"
 #include "mount.h"
+#include "union.h"
 
 /* [Feb-1997 T. Schoebel-Theuer]
  * Fundamental changes in the pathname lookup mechanisms (namei)
@@ -2891,6 +2892,11 @@ static long do_rmdir(int dfd, const char __user *pathname)
 	if (error)
 		return error;
 
+	/* rmdir() on union mounts not implemented yet */
+	error = -EINVAL;
+	if (IS_DIR_UNIONED(nd.path.dentry))
+		goto exit1;
+
 	switch(nd.last_type) {
 	case LAST_DOTDOT:
 		error = -ENOTEMPTY;
@@ -2991,6 +2997,11 @@ static long do_unlinkat(int dfd, const char __user *pathname)
 	if (nd.last_type != LAST_NORM)
 		goto exit1;
 
+	/* unlink() on union mounts not implemented yet */
+	error = -EINVAL;
+	if (IS_DIR_UNIONED(nd.path.dentry))
+		goto exit1;
+
 	nd.flags &= ~LOOKUP_PARENT;
 
 	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
@@ -3384,6 +3395,12 @@ SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
 	if (oldnd.path.mnt != newnd.path.mnt)
 		goto exit2;
 
+	/* rename() on union mounts not implemented yet */
+	error = -EXDEV;
+	if (IS_DIR_UNIONED(oldnd.path.dentry) ||
+	    IS_DIR_UNIONED(newnd.path.dentry))
+		goto exit2;
+
 	old_dir = oldnd.path.dentry;
 	error = -EBUSY;
 	if (oldnd.last_type != LAST_NORM)

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