expand_number: Tighten check of unit.

The current code silently ignores characters after the unit as long
the unit themselves were recognized. This commit makes expand_number(3)
to fail with EINVAL if buf did not terminate after the unit character.

Historically, the function accepts and ignores "B" as a SI unit, this
behavior is preserved and e.g. KB, MB are still accepted as aliases of
K and M, document this behavior in the manual page.

While I am there, also write a few test cases to validate the behavior.

Reviewed-by:	emaste
MFC-after:	2 weeks
Differential Revision: https://reviews.freebsd.org/D40482

1 files changed, 14 insertions, 0 deletions

diff --git a/lib/libutil/expand_number.c b/lib/libutil/expand_number.c
index f34db013ff18..61b73039f3bd 100644
--- a/lib/libutil/expand_number.c
+++ b/lib/libutil/expand_number.c
@@ -76,6 +76,8 @@ expand_number(const char *buf, uint64_t *num)
 		shift = 10;
 		break;
 	case 'b':
+		shift = 0;
+		break;
 	case '\0': /* No unit. */
 		*num = number;
 		return (0);
@@ -85,6 +87,18 @@ expand_number(const char *buf, uint64_t *num)
 		return (-1);
 	}
 
+	/*
+	 * Treat 'b' as an ignored suffix for all unit except 'b',
+	 * otherwise there should be no remaining character(s).
+	 */
+	endptr++;
+	if (shift != 0 && tolower((unsigned char)*endptr) == 'b')
+		endptr++;
+	if (*endptr != '\0') {
+		errno = EINVAL;
+		return (-1);
+	}
+
 	if ((number << shift) >> shift != number) {
 		/* Overflow */
 		errno = ERANGE;