efivarfs: return accurate error code in efivarfs_fill_super()

Joseph was hitting a failure case when mounting efivarfs which
resulted in an incorrect error message,

  $ sudo mount -v /sys/firmware/efi/efivars mount: Cannot allocate memory

triggered when efivarfs_valid_name() returned -EINVAL.

Make sure we pass accurate return values up the stack if
efivarfs_fill_super() fails to build inodes for EFI variables.

Reported-by: Joseph Yasi <joe.yasi@gmail.com>
Reported-by: Lingzhu Xiang <lxiang@redhat.com>
Cc: Josh Boyer <jwboyer@redhat.com>
Cc: Jeremy Kerr <jk@ozlabs.org>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: <stable@vger.kernel.org> # v3.8
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

1 files changed, 15 insertions, 5 deletions

diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index 1b9a6e17e3dc..bea32d1ef7d5 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -1163,15 +1163,22 @@ static struct dentry_operations efivarfs_d_ops = {
 
 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
 {
+        struct dentry *d;
         struct qstr q;
+        int err;
 
         q.name = name;
         q.len = strlen(name);
 
-        if (efivarfs_d_hash(NULL, NULL, &q))
-                return NULL;
+        err = efivarfs_d_hash(NULL, NULL, &q);
+        if (err)
+                return ERR_PTR(err);
+
+        d = d_alloc(parent, &q);
+        if (d)
+                return d;
 
-        return d_alloc(parent, &q);
+        return ERR_PTR(-ENOMEM);
 }
 
 static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
@@ -1181,6 +1188,7 @@ static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
         struct efivar_entry *entry, *n;
         struct efivars *efivars = &__efivars;
         char *name;
+        int err = -ENOMEM;
 
         efivarfs_sb = sb;
 
@@ -1231,8 +1239,10 @@ static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
                         goto fail_name;
 
                 dentry = efivarfs_alloc_dentry(root, name);
-                if (!dentry)
+                if (IS_ERR(dentry)) {
+                        err = PTR_ERR(dentry);
                         goto fail_inode;
+                }
 
                 /* copied by the above to local storage in the dentry. */
                 kfree(name);
@@ -1259,7 +1269,7 @@ fail_inode:
 fail_name:
         kfree(name);
 fail:
-        return -ENOMEM;
+        return err;
 }
 
 static struct dentry *efivarfs_mount(struct file_system_type *fs_type,