efi_loader: efi_dp_check_length()
We need to check that device paths provided via UEFI variables are not
malformed.
Provide function efi_dp_check_length() to check if a device path has an
end node within a given number of bytes.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/lib/efi_loader/efi_device_path.c b/lib/efi_loader/efi_device_path.c
index 7ae14f3..8a5c13c 100644
--- a/lib/efi_loader/efi_device_path.c
+++ b/lib/efi_loader/efi_device_path.c
@@ -1127,3 +1127,36 @@
return EFI_SUCCESS;
}
+
+/**
+ * efi_dp_check_length() - check length of a device path
+ *
+ * @dp: pointer to device path
+ * @maxlen: maximum length of the device path
+ * Return:
+ * * length of the device path if it is less or equal @maxlen
+ * * -1 if the device path is longer then @maxlen
+ * * -1 if a device path node has a length of less than 4
+ * * -EINVAL if maxlen exceeds SSIZE_MAX
+ */
+ssize_t efi_dp_check_length(const struct efi_device_path *dp,
+ const size_t maxlen)
+{
+ ssize_t ret = 0;
+ u16 len;
+
+ if (maxlen > SSIZE_MAX)
+ return -EINVAL;
+ for (;;) {
+ len = dp->length;
+ if (len < 4)
+ return -1;
+ ret += len;
+ if (ret > maxlen)
+ return -1;
+ if (dp->type == DEVICE_PATH_TYPE_END &&
+ dp->sub_type == DEVICE_PATH_SUB_TYPE_END)
+ return ret;
+ dp = (const struct efi_device_path *)((const u8 *)dp + len);
+ }
+}