namei.c: let follow_link() do put_link() on failure

no need for kludgy "set cookie to ERR_PTR(...) because we failed
before we did actual ->follow_link() and want to suppress put_link()",
no pointless check in put_link() itself.

Callers checked if follow_link() has failed anyway; might as well
break out of their loops if that happened, without bothering
to call put_link() first.

[AV: folded fixes from hch]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 41 insertions, 33 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 7d694194024a..6135a14d5a84 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -605,7 +605,7 @@ static inline void path_to_nameidata(const struct path *path,
 static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
 {
         struct inode *inode = link->dentry->d_inode;
-        if (!IS_ERR(cookie) && inode->i_op->put_link)
+        if (inode->i_op->put_link)
                 inode->i_op->put_link(link->dentry, nd, cookie);
         path_put(link);
 }
@@ -613,19 +613,19 @@ static inline void put_link(struct nameidata *nd, struct path *link, void *cooki
 static __always_inline int
 follow_link(struct path *link, struct nameidata *nd, void **p)
 {
-        int error;
         struct dentry *dentry = link->dentry;
+        int error;
+        char *s;
 
         BUG_ON(nd->flags & LOOKUP_RCU);
 
         if (link->mnt == nd->path.mnt)
                 mntget(link->mnt);
 
-        if (unlikely(current->total_link_count >= 40)) {
-                *p = ERR_PTR(-ELOOP); /* no ->put_link(), please */
-                path_put(&nd->path);
-                return -ELOOP;
-        }
+        error = -ELOOP;
+        if (unlikely(current->total_link_count >= 40))
+                goto out_put_nd_path;
+
         cond_resched();
         current->total_link_count++;
 
@@ -633,30 +633,37 @@ follow_link(struct path *link, struct nameidata *nd, void **p)
         nd_set_link(nd, NULL);
 
         error = security_inode_follow_link(link->dentry, nd);
-        if (error) {
-                *p = ERR_PTR(error); /* no ->put_link(), please */
-                path_put(&nd->path);
-                return error;
-        }
+        if (error)
+                goto out_put_nd_path;
 
         nd->last_type = LAST_BIND;
         *p = dentry->d_inode->i_op->follow_link(dentry, nd);
         error = PTR_ERR(*p);
-        if (!IS_ERR(*p)) {
-                char *s = nd_get_link(nd);
-                error = 0;
-                if (s)
-                        error = __vfs_follow_link(nd, s);
-                else if (nd->last_type == LAST_BIND) {
-                        nd->flags |= LOOKUP_JUMPED;
-                        nd->inode = nd->path.dentry->d_inode;
-                        if (nd->inode->i_op->follow_link) {
-                                /* stepped on a _really_ weird one */
-                                path_put(&nd->path);
-                                error = -ELOOP;
-                        }
+        if (IS_ERR(*p))
+                goto out_put_link;
+
+        error = 0;
+        s = nd_get_link(nd);
+        if (s) {
+                error = __vfs_follow_link(nd, s);
+        } else if (nd->last_type == LAST_BIND) {
+                nd->flags |= LOOKUP_JUMPED;
+                nd->inode = nd->path.dentry->d_inode;
+                if (nd->inode->i_op->follow_link) {
+                        /* stepped on a _really_ weird one */
+                        path_put(&nd->path);
+                        error = -ELOOP;
                 }
         }
+        if (unlikely(error))
+                put_link(nd, link, *p);
+
+        return error;
+
+out_put_nd_path:
+        path_put(&nd->path);
+out_put_link:
+        path_put(link);
         return error;
 }
 
@@ -1383,9 +1390,10 @@ static inline int nested_symlink(struct path *path, struct nameidata *nd)
                 void *cookie;
 
                 res = follow_link(&link, nd, &cookie);
-                if (!res)
-                        res = walk_component(nd, path, &nd->last,
-                                             nd->last_type, LOOKUP_FOLLOW);
+                if (res)
+                        break;
+                res = walk_component(nd, path, &nd->last,
+                                     nd->last_type, LOOKUP_FOLLOW);
                 put_link(nd, &link, cookie);
         } while (res > 0);
 
@@ -1777,8 +1785,9 @@ static int path_lookupat(int dfd, const char *name,
                         struct path link = path;
                         nd->flags |= LOOKUP_PARENT;
                         err = follow_link(&link, nd, &cookie);
-                        if (!err)
-                                err = lookup_last(nd, &path);
+                        if (err)
+                                break;
+                        err = lookup_last(nd, &path);
                         put_link(nd, &link, cookie);
                 }
         }
@@ -2475,9 +2484,8 @@ static struct file *path_openat(int dfd, const char *pathname,
                 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
                 error = follow_link(&link, nd, &cookie);
                 if (unlikely(error))
-                        filp = ERR_PTR(error);
-                else
-                        filp = do_last(nd, &path, op, pathname);
+                        goto out_filp;
+                filp = do_last(nd, &path, op, pathname);
                 put_link(nd, &link, cookie);
         }
 out: