efivar: handle error when reading --fromfile

The result of read() was stored in an unsigned variable, so the
test for a negative value would never work.

While I'm here, print a better error message for an empty file,
omitting the misleading errno message.

Reported by:	Coverity
MFC after:	1 week
Sponsored by:	Dell EMC Isilon
This commit is contained in:
Eric van Gyzen 2022-02-23 12:15:34 -06:00
parent 331b84b5db
commit d0f4e583bf

View file

@ -239,8 +239,10 @@ print_var(efi_guid_t *guid, char *name)
if (data == NULL)
rep_err(1, "malloc");
datalen = read(fd, data, 64 * 1024);
if (datalen <= 0)
if ((ssize_t)datalen < 0)
rep_err(1, "read");
if (datalen == 0)
rep_errx(1, "empty file");
close(fd);
} else {
rv = efi_get_variable(*guid, name, &data, &datalen, &att);