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

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

[Rafael J. Wysocki]

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;

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

[Tejun Heo]

Hello, Rafael.

Rafael J. Wysocki wrote:
> 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;

Argh... Right.  My delusional mind somehow thought the nonsense early
dereferencing was there before any changes so I passed on that one.
Thanks a lot for catching it.  The whole sysfs patchset is pending
regeneration.  I'll include the fix patch.

Thanks a lot.  :-)

-- 
tejun