parse_unit_factor() checks if a K, M or G is present after a number and
multiplies it by 2^10, 2^20 or 2^30, respectively. One of its callers
checks if the result is smaller than the number alone to detect
overflows. The other one passes 1 as the number and does multiplication
and overflow check itself in a similar manner.
This works, but is inconsistent, and it would break if we added support
for a bigger unit factor. E.g. 16777217T is 2^64 + 2^40, i.e. too big
for a 64-bit number. Modulo 2^64 we get 2^40 == 1TB, which is bigger
than the raw number 16777217 == 2^24 + 1, so the overflow would go
undetected by that method.
Let both callers pass 1 and handle overflow check and multiplication
themselves. Do the check before the multiplication, using
unsigned_mult_overflows, which is simpler and can deal with larger unit
factors.
Signed-off-by: Rene Scharfe <l.s.r@xxxxxx>
---
Patch generated with --function-context for easier review (e.g. to see
why we can stop updating uval in place).
config.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/config.c b/config.c
index 01c6e9df23..3c00369ba8 100644
--- a/config.c
+++ b/config.c
@@ -856,29 +856,29 @@ static int parse_unit_factor(const char *end, uintmax_t *val)
static int git_parse_signed(const char *value, intmax_t *ret, intmax_t max)
{
if (value && *value) {
char *end;
intmax_t val;
uintmax_t uval;
uintmax_t factor = 1;
errno = 0;
val = strtoimax(value, &end, 0);
if (errno == ERANGE)
return 0;
if (!parse_unit_factor(end, &factor)) {
errno = EINVAL;
return 0;
}
uval = val < 0 ? -val : val;
- uval *= factor;
- if (uval > max || (val < 0 ? -val : val) > uval) {
+ if (unsigned_mult_overflows(factor, uval) ||
+ factor * uval > max) {
errno = ERANGE;
return 0;
}
val *= factor;
*ret = val;
return 1;
}
errno = EINVAL;
return 0;
}
@@ -886,26 +886,27 @@ static int git_parse_signed(const char *value, intmax_t *ret, intmax_t max)
static int git_parse_unsigned(const char *value, uintmax_t *ret, uintmax_t max)
{
if (value && *value) {
char *end;
uintmax_t val;
- uintmax_t oldval;
+ uintmax_t factor = 1;
errno = 0;
val = strtoumax(value, &end, 0);
if (errno == ERANGE)
return 0;
- oldval = val;
- if (!parse_unit_factor(end, &val)) {
+ if (!parse_unit_factor(end, &factor)) {
errno = EINVAL;
return 0;
}
- if (val > max || oldval > val) {
+ if (unsigned_mult_overflows(factor, val) ||
+ factor * val > max) {
errno = ERANGE;
return 0;
}
+ val *= factor;
*ret = val;
return 1;
}
errno = EINVAL;
return 0;
}
--
2.22.0
