2 files changed, 35 insertions, 9 deletions

diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index 9ac934018bba..d6b8d2f628fa 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -694,28 +694,51 @@ static ssize_t efivarfs_file_write(struct file *file,
         struct inode *inode = file->f_mapping->host;
         unsigned long datasize = count - sizeof(attributes);
         unsigned long newdatasize;
+        u64 storage_size, remaining_size, max_size;
         ssize_t bytes = 0;
 
         if (count < sizeof(attributes))
                 return -EINVAL;
 
-        data = kmalloc(datasize, GFP_KERNEL);
+        if (copy_from_user(&attributes, userbuf, sizeof(attributes)))
+                return -EFAULT;
 
-        if (!data)
-                return -ENOMEM;
+        if (attributes & ~(EFI_VARIABLE_MASK))
+                return -EINVAL;
 
         efivars = var->efivars;
 
-        if (copy_from_user(&attributes, userbuf, sizeof(attributes))) {
-                bytes = -EFAULT;
-                goto out;
+        /*
+         * Ensure that the user can't allocate arbitrarily large
+         * amounts of memory. Pick a default size of 64K if
+         * QueryVariableInfo() isn't supported by the firmware.
+         */
+        spin_lock(&efivars->lock);
+
+        if (!efivars->ops->query_variable_info)
+                status = EFI_UNSUPPORTED;
+        else {
+                const struct efivar_operations *fops = efivars->ops;
+                status = fops->query_variable_info(attributes, &storage_size,
+                                                   &remaining_size, &max_size);
         }
 
-        if (attributes & ~(EFI_VARIABLE_MASK)) {
-                bytes = -EINVAL;
-                goto out;
+        spin_unlock(&efivars->lock);
+
+        if (status != EFI_SUCCESS) {
+                if (status != EFI_UNSUPPORTED)
+                        return efi_status_to_err(status);
+
+                remaining_size = 65536;
         }
 
+        if (datasize > remaining_size)
+                return -ENOSPC;
+
+        data = kmalloc(datasize, GFP_KERNEL);
+        if (!data)
+                return -ENOMEM;
+
         if (copy_from_user(data, userbuf + sizeof(attributes), datasize)) {
                 bytes = -EFAULT;
                 goto out;
@@ -1709,6 +1732,8 @@ efivars_init(void)
         ops.get_variable = efi.get_variable;
         ops.set_variable = efi.set_variable;
         ops.get_next_variable = efi.get_next_variable;
+        ops.query_variable_info = efi.query_variable_info;
+
         error = register_efivars(&__efivars, &ops, efi_kobj);
         if (error)
                 goto err_put;
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 5e2308d9c6be..f80079cd84f4 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -646,6 +646,7 @@ struct efivar_operations {
         efi_get_variable_t *get_variable;
         efi_get_next_variable_t *get_next_variable;
         efi_set_variable_t *set_variable;
+        efi_query_variable_info_t *query_variable_info;
 };
 
 struct efivars {