ecryptfs: fix failure handling in ->readlink()

If ecryptfs_readlink_lower() fails, buf remains an uninitialized
pointer and passing it nd_set_link() won't do anything good.

Fixed by switching ecryptfs_readlink_lower() to saner API - make it
return buf or ERR_PTR(...) and update callers.

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

1 files changed, 13 insertions, 16 deletions

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index c36c44824471..b167ca48b8ee 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -659,19 +659,17 @@ out_lock:
         return rc;
 }
 
-static int ecryptfs_readlink_lower(struct dentry *dentry, char **buf,
-                                   size_t *bufsiz)
+static char *ecryptfs_readlink_lower(struct dentry *dentry, size_t *bufsiz)
 {
         struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);
         char *lower_buf;
+        char *buf;
         mm_segment_t old_fs;
         int rc;
 
         lower_buf = kmalloc(PATH_MAX, GFP_KERNEL);
-        if (!lower_buf) {
-                rc = -ENOMEM;
-                goto out;
-        }
+        if (!lower_buf)
+                return ERR_PTR(-ENOMEM);
         old_fs = get_fs();
         set_fs(get_ds());
         rc = lower_dentry->d_inode->i_op->readlink(lower_dentry,
@@ -680,21 +678,18 @@ static int ecryptfs_readlink_lower(struct dentry *dentry, char **buf,
         set_fs(old_fs);
         if (rc < 0)
                 goto out;
-        rc = ecryptfs_decode_and_decrypt_filename(buf, bufsiz, dentry->d_sb,
+        rc = ecryptfs_decode_and_decrypt_filename(&buf, bufsiz, dentry->d_sb,
                                                   lower_buf, rc);
 out:
         kfree(lower_buf);
-        return rc;
+        return rc ? ERR_PTR(rc) : buf;
 }
 
 static void *ecryptfs_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
-        char *buf;
-        size_t len = PATH_MAX;
-        int rc;
-
-        rc = ecryptfs_readlink_lower(dentry, &buf, &len);
-        if (rc)
+        size_t len;
+        char *buf = ecryptfs_readlink_lower(dentry, &len);
+        if (IS_ERR(buf))
                 goto out;
         fsstack_copy_attr_atime(dentry->d_inode,
                                 ecryptfs_dentry_to_lower(dentry)->d_inode);
@@ -1003,10 +998,12 @@ static int ecryptfs_getattr_link(struct vfsmount *mnt, struct dentry *dentry,
                 char *target;
                 size_t targetsiz;
 
-                rc = ecryptfs_readlink_lower(dentry, &target, &targetsiz);
-                if (!rc) {
+                target = ecryptfs_readlink_lower(dentry, &targetsiz);
+                if (!IS_ERR(target)) {
                         kfree(target);
                         stat->size = targetsiz;
+                } else {
+                        rc = PTR_ERR(target);
                 }
         }
         return rc;