fs: namei fix ->put_link on wrong inode in do_filp_open

J. R. Okajima noticed that ->put_link is being attempted on the
wrong inode, and suggested the way to fix it. I changed it a bit
according to Al's suggestion to keep an explicit link path around.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>

1 files changed, 19 insertions, 18 deletions

diff --git a/fs/namei.c b/fs/namei.c
index bc24894c5f14..9cda4c452a6d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -779,7 +779,8 @@ static void path_put_conditional(struct path *path, struct nameidata *nd)
                 mntput(path->mnt);
 }
 
-static inline void path_to_nameidata(struct path *path, struct nameidata *nd)
+static inline void path_to_nameidata(const struct path *path,
+                                        struct nameidata *nd)
 {
         if (!(nd->flags & LOOKUP_RCU)) {
                 dput(nd->path.dentry);
@@ -791,20 +792,20 @@ static inline void path_to_nameidata(struct path *path, struct nameidata *nd)
 }
 
 static __always_inline int
-__do_follow_link(struct path *path, struct nameidata *nd, void **p)
+__do_follow_link(const struct path *link, struct nameidata *nd, void **p)
 {
         int error;
-        struct dentry *dentry = path->dentry;
+        struct dentry *dentry = link->dentry;
 
-        touch_atime(path->mnt, dentry);
+        touch_atime(link->mnt, dentry);
         nd_set_link(nd, NULL);
 
-        if (path->mnt != nd->path.mnt) {
-                path_to_nameidata(path, nd);
+        if (link->mnt != nd->path.mnt) {
+                path_to_nameidata(link, nd);
                 nd->inode = nd->path.dentry->d_inode;
                 dget(dentry);
         }
-        mntget(path->mnt);
+        mntget(link->mnt);
 
         nd->last_type = LAST_BIND;
         *p = dentry->d_inode->i_op->follow_link(dentry, nd);
@@ -2347,11 +2348,12 @@ reval:
         nd.flags = flags;
         filp = do_last(&nd, &path, open_flag, acc_mode, mode, pathname);
         while (unlikely(!filp)) { /* trailing symlink */
-                struct path holder;
+                struct path link = path;
+                struct inode *linki = link.dentry->d_inode;
                 void *cookie;
                 error = -ELOOP;
                 /* S_ISDIR part is a temporary automount kludge */
-                if (!(nd.flags & LOOKUP_FOLLOW) && !S_ISDIR(nd.inode->i_mode))
+                if (!(nd.flags & LOOKUP_FOLLOW) && !S_ISDIR(linki->i_mode))
                         goto exit_dput;
                 if (count++ == 32)
                         goto exit_dput;
@@ -2367,23 +2369,22 @@ reval:
                  * just set LAST_BIND.
                  */
                 nd.flags |= LOOKUP_PARENT;
-                error = security_inode_follow_link(path.dentry, &nd);
+                error = security_inode_follow_link(link.dentry, &nd);
                 if (error)
                         goto exit_dput;
-                error = __do_follow_link(&path, &nd, &cookie);
+                error = __do_follow_link(&link, &nd, &cookie);
                 if (unlikely(error)) {
-                        if (!IS_ERR(cookie) && nd.inode->i_op->put_link)
-                                nd.inode->i_op->put_link(path.dentry, &nd, cookie);
+                        if (!IS_ERR(cookie) && linki->i_op->put_link)
+                                linki->i_op->put_link(link.dentry, &nd, cookie);
                         /* nd.path had been dropped */
-                        nd.path = path;
+                        nd.path = link;
                         goto out_path;
                 }
-                holder = path;
                 nd.flags &= ~LOOKUP_PARENT;
                 filp = do_last(&nd, &path, open_flag, acc_mode, mode, pathname);
-                if (nd.inode->i_op->put_link)
-                        nd.inode->i_op->put_link(holder.dentry, &nd, cookie);
-                path_put(&holder);
+                if (linki->i_op->put_link)
+                        linki->i_op->put_link(link.dentry, &nd, cookie);
+                path_put(&link);
         }
 out:
         if (nd.root.mnt)