kernfs: do not alloc iattrs in kernfs_xattr_get

This is a read-only operation, so we can simply return -ENODATA if
kn->iattr is NULL.

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
[PM: minor merge fixes]
Signed-off-by: Paul Moore <paul@paul-moore.com>

diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index 7d30b4949a8465d6b95c402390cc4c1f707d629f..5c5569fb2110f8b089e548ce07bcec503f0eab92 100644 (file)
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -31,14 +31,14 @@ static const struct inode_operations kernfs_iops = {
        .listxattr      = kernfs_iop_listxattr,
 };
 
-static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
+static struct kernfs_iattrs *__kernfs_iattrs(struct kernfs_node *kn, int alloc)
 {
        static DEFINE_MUTEX(iattr_mutex);
        struct kernfs_iattrs *ret;
 
        mutex_lock(&iattr_mutex);
 
-       if (kn->iattr)
+       if (kn->iattr || !alloc)
                goto out_unlock;
 
        kn->iattr = kmem_cache_zalloc(kernfs_iattrs_cache, GFP_KERNEL);
@@ -60,6 +60,16 @@ out_unlock:
        return ret;
 }
 
+static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
+{
+       return __kernfs_iattrs(kn, 1);
+}
+
+static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn)
+{
+       return __kernfs_iattrs(kn, 0);
+}
+
 int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
 {
        struct kernfs_iattrs *attrs;
@@ -306,9 +316,9 @@ static int kernfs_xattr_get(const struct xattr_handler *handler,
        struct kernfs_node *kn = inode->i_private;
        struct kernfs_iattrs *attrs;
 
-       attrs = kernfs_iattrs(kn);
+       attrs = kernfs_iattrs_noalloc(kn);
        if (!attrs)
-               return -ENOMEM;
+               return -ENODATA;
 
        return simple_xattr_get(&attrs->xattrs, name, value, size);
 }