sysfs: Fix oops in sysfs_drop_dentry on x86_64

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>
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index 732fd7f371e..ee31bf369a8 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -285,7 +285,7 @@ void sysfs_drop_dentry(struct sysfs_dirent *sd)
 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 * dir, const char * name)
                 /* 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;