[PATCH] strtoul_ui: reject negative values

[Matthieu Moy <Matthieu.Moy@imag.fr>]

strtoul_ui uses strtoul to get a long unsigned, then checks that casting
to unsigned does not lose information and return the casted value.

On 64 bits architecture, checking that the cast does not change the value
catches most errors, but when sizeof(int) == sizeof(long) (e.g. i386),
the check does nothing. Unfortunately, strtoul silently accepts negative
values, and as a result strtoul_ui("-1", ...) raised no error.

This patch catches negative values before it's too late, i.e. before
calling strtoul. We still silently accept very large integers that wrap
to a valid "unsigned int".

Reported-by: Max Kirillov <max@max630.net>
Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
---
So, here's a proper patch (I mean, a band-aid patch, but properly
send ;-) ).

It should be merged before Kartik's series (or inserted at the start
of the series) so that we get the fix before the test breakage.

 git-compat-util.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/git-compat-util.h b/git-compat-util.h
index f649e81..1df82fa 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -814,6 +814,9 @@ static inline int strtoul_ui(char const *s, int base, unsigned int *result)
 	char *p;
 
 	errno = 0;
+	/* negative values would be accepted by strtoul */
+	if (strchr(s, '-'))
+		return -1;
 	ul = strtoul(s, &p, base);
 	if (errno || *p || p == s || (unsigned int) ul != ul)
 		return -1;
-- 
2.5.0.402.g8854c44