Fix race between proc_get_inode() and remove_proc_entry()

proc_lookup				remove_proc_entry
===========				=================

lock_kernel();
spin_lock(&proc_subdir_lock);
[find PDE with refcount 0]
spin_unlock(&proc_subdir_lock);
					spin_lock(&proc_subdir_lock);
					[find PDE with refcount 0]
					[check refcount and free PDE]
					spin_unlock(&proc_subdir_lock);
proc_get_inode:
	de_get(de); /* boom */

Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 775fb21294d8..22a08ff3475d 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -398,6 +398,7 @@ struct dentry *proc_lookup(struct inode * dir, struct dentry *dentry, struct nam
                         if (!memcmp(dentry->d_name.name, de->name, de->namelen)) {
                                 unsigned int ino = de->low_ino;
 
+                                de_get(de);
                                 spin_unlock(&proc_subdir_lock);
                                 error = -EINVAL;
                                 inode = proc_get_inode(dir->i_sb, ino, de);
@@ -414,6 +415,7 @@ struct dentry *proc_lookup(struct inode * dir, struct dentry *dentry, struct nam
                 d_add(dentry, inode);
                 return NULL;
         }
+        de_put(de);
         return ERR_PTR(error);
 }