[PATCH -mm] sysfs: Fix oops in sysfs_drop_dentry on x86_64

["Rafael J. Wysocki" <rjw@sisk.pl>]

From: Rafael J. Wysocki <rjw@sisk.pl>

Fix oops on x86_64 caused by the dereference of dir in sysfs_drop_dentry() made
before checking if dir is not NULL
(cf. http://marc.info/?l=linux-kernel&m=118151626704924&w=2).

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 fs/sysfs/inode.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-2.6.22-rc4-mm2/fs/sysfs/inode.c
===================================================================
--- linux-2.6.22-rc4-mm2.orig/fs/sysfs/inode.c
+++ linux-2.6.22-rc4-mm2/fs/sysfs/inode.c
@@ -285,7 +285,7 @@ void sysfs_drop_dentry(struct sysfs_dire
 int sysfs_hash_and_remove(struct dentry * dir, const char * name)
 {
 	struct sysfs_dirent **pos, *sd;
-	struct sysfs_dirent *parent_sd = dir->d_fsdata;
+	struct sysfs_dirent *parent_sd;
 	int found = 0;
 
 	if (!dir)
@@ -295,6 +295,7 @@ int sysfs_hash_and_remove(struct dentry 
 		/* no inode means this hasn't been made visible yet */
 		return -ENOENT;
 
+	parent_sd = dir->d_fsdata;
 	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
 	for (pos = &parent_sd->s_children; *pos; pos = &(*pos)->s_sibling) {
 		sd = *pos;