Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6:
  nd->inode is not set on the second attempt in path_walk()
  unfuck proc_sysctl ->d_compare()
  minimal fix for do_filp_open() race

fs/namei.c

@@ -1546,6 +1546,7 @@ static int path_walk(const char *name, struct nameidata *nd)
 		/* nd->path had been dropped */
 		current->total_link_count = 0;
 		nd->path = save;
+		nd->inode = save.dentry->d_inode;
 		path_get(&nd->path);
 		nd->flags |= LOOKUP_REVAL;
 		result = link_path_walk(name, nd);
@@ -2455,22 +2456,29 @@ struct file *do_filp_open(int dfd, const char *pathname,
 	/* !O_CREAT, simple open */
 	error = do_path_lookup(dfd, pathname, flags, &nd);
 	if (unlikely(error))
-		goto out_filp;
+		goto out_filp2;
 	error = -ELOOP;
 	if (!(nd.flags & LOOKUP_FOLLOW)) {
 		if (nd.inode->i_op->follow_link)
-			goto out_path;
+			goto out_path2;
 	}
 	error = -ENOTDIR;
 	if (nd.flags & LOOKUP_DIRECTORY) {
 		if (!nd.inode->i_op->lookup)
-			goto out_path;
+			goto out_path2;
 	}
 	audit_inode(pathname, nd.path.dentry);
 	filp = finish_open(&nd, open_flag, acc_mode);
+out2:
 	release_open_intent(&nd);
 	return filp;
 
+out_path2:
+	path_put(&nd.path);
+out_filp2:
+	filp = ERR_PTR(error);
+	goto out2;
+
 creat:
 	/* OK, have to create the file. Find the parent. */
 	error = path_init_rcu(dfd, pathname,

fs/proc/inode.c

@@ -27,6 +27,7 @@
 static void proc_evict_inode(struct inode *inode)
 {
 	struct proc_dir_entry *de;
+	struct ctl_table_header *head;
 
 	truncate_inode_pages(&inode->i_data, 0);
 	end_writeback(inode);
@@ -38,8 +39,11 @@ static void proc_evict_inode(struct inode *inode)
 	de = PROC_I(inode)->pde;
 	if (de)
 		pde_put(de);
-	if (PROC_I(inode)->sysctl)
-		sysctl_head_put(PROC_I(inode)->sysctl);
+	head = PROC_I(inode)->sysctl;
+	if (head) {
+		rcu_assign_pointer(PROC_I(inode)->sysctl, NULL);
+		sysctl_head_put(head);
+	}
 }
 
 struct vfsmount *proc_mnt;

fs/proc/proc_sysctl.c

@@ -408,15 +408,18 @@ static int proc_sys_compare(const struct dentry *parent,
 		const struct dentry *dentry, const struct inode *inode,
 		unsigned int len, const char *str, const struct qstr *name)
 {
+	struct ctl_table_header *head;
 	/* Although proc doesn't have negative dentries, rcu-walk means
 	 * that inode here can be NULL */
+	/* AV: can it, indeed? */
 	if (!inode)
-		return 0;
+		return 1;
 	if (name->len != len)
 		return 1;
 	if (memcmp(name->name, str, len))
 		return 1;
-	return !sysctl_is_seen(PROC_I(inode)->sysctl);
+	head = rcu_dereference(PROC_I(inode)->sysctl);
+	return !head || !sysctl_is_seen(head);
 }
 
 static const struct dentry_operations proc_sys_dentry_operations = {

include/linux/sysctl.h

@@ -25,6 +25,7 @@
 #include <linux/kernel.h>
 #include <linux/types.h>
 #include <linux/compiler.h>
+#include <linux/rcupdate.h>
 
 struct completion;
 
@@ -1037,10 +1038,15 @@ struct ctl_table_root {
    struct ctl_table trees. */
 struct ctl_table_header
 {
+	union {
+		struct {
 			struct ctl_table *ctl_table;
 			struct list_head ctl_entry;
 			int used;
 			int count;
+		};
+		struct rcu_head rcu;
+	};
 	struct completion *unregistering;
 	struct ctl_table *ctl_table_arg;
 	struct ctl_table_root *root;

kernel/sysctl.c

@@ -194,9 +194,9 @@ static int sysrq_sysctl_handler(ctl_table *table, int write,
 static struct ctl_table root_table[];
 static struct ctl_table_root sysctl_table_root;
 static struct ctl_table_header root_table_header = {
-	.count = 1,
+	{{.count = 1,
 	.ctl_table = root_table,
-	.ctl_entry = LIST_HEAD_INIT(sysctl_table_root.default_set.list),
+	.ctl_entry = LIST_HEAD_INIT(sysctl_table_root.default_set.list),}},
 	.root = &sysctl_table_root,
 	.set = &sysctl_table_root.default_set,
 };
@@ -1567,11 +1567,16 @@ void sysctl_head_get(struct ctl_table_header *head)
 	spin_unlock(&sysctl_lock);
 }
 
+static void free_head(struct rcu_head *rcu)
+{
+	kfree(container_of(rcu, struct ctl_table_header, rcu));
+}
+
 void sysctl_head_put(struct ctl_table_header *head)
 {
 	spin_lock(&sysctl_lock);
 	if (!--head->count)
-		kfree(head);
+		call_rcu(&head->rcu, free_head);
 	spin_unlock(&sysctl_lock);
 }
 
@@ -1948,10 +1953,10 @@ void unregister_sysctl_table(struct ctl_table_header * header)
 	start_unregistering(header);
 	if (!--header->parent->count) {
 		WARN_ON(1);
-		kfree(header->parent);
+		call_rcu(&header->parent->rcu, free_head);
 	}
 	if (!--header->count)
-		kfree(header);
+		call_rcu(&header->rcu, free_head);
 	spin_unlock(&sysctl_lock);
 }