path.c: fix uninitialized memory access

In cleanup_path we're passing in a char array, run a memcmp on it, and
run through it without ever checking if something is in the array in the
first place.  This can lead us to access uninitialized memory, for
example in t5541-http-push-smart.sh test 7, when run under valgrind:

==4423== Conditional jump or move depends on uninitialised value(s)
==4423==    at 0x242FA9: cleanup_path (path.c:35)
==4423==    by 0x242FA9: mkpath (path.c:456)
==4423==    by 0x256CC7: refname_match (refs.c:364)
==4423==    by 0x26C181: count_refspec_match (remote.c:1015)
==4423==    by 0x26C181: match_explicit_lhs (remote.c:1126)
==4423==    by 0x26C181: check_push_refs (remote.c:1409)
==4423==    by 0x2ABB4D: transport_push (transport.c:870)
==4423==    by 0x186703: push_with_options (push.c:332)
==4423==    by 0x18746D: do_push (push.c:409)
==4423==    by 0x18746D: cmd_push (push.c:566)
==4423==    by 0x1183E0: run_builtin (git.c:352)
==4423==    by 0x11973E: handle_builtin (git.c:539)
==4423==    by 0x11973E: run_argv (git.c:593)
==4423==    by 0x11973E: main (git.c:698)
==4423==  Uninitialised value was created by a heap allocation
==4423==    at 0x4C2CD8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4423==    by 0x4C2F195: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4423==    by 0x2C196B: xrealloc (wrapper.c:137)
==4423==    by 0x29A30B: strbuf_grow (strbuf.c:66)
==4423==    by 0x29A30B: strbuf_vaddf (strbuf.c:277)
==4423==    by 0x242F9F: mkpath (path.c:454)
==4423==    by 0x256CC7: refname_match (refs.c:364)
==4423==    by 0x26C181: count_refspec_match (remote.c:1015)
==4423==    by 0x26C181: match_explicit_lhs (remote.c:1126)
==4423==    by 0x26C181: check_push_refs (remote.c:1409)
==4423==    by 0x2ABB4D: transport_push (transport.c:870)
==4423==    by 0x186703: push_with_options (push.c:332)
==4423==    by 0x18746D: do_push (push.c:409)
==4423==    by 0x18746D: cmd_push (push.c:566)
==4423==    by 0x1183E0: run_builtin (git.c:352)
==4423==    by 0x11973E: handle_builtin (git.c:539)
==4423==    by 0x11973E: run_argv (git.c:593)
==4423==    by 0x11973E: main (git.c:698)
==4423==

Avoid this by using skip_prefix(), which knows not to go beyond the
end of the string.

Reported-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/path.c b/path.c
index e50d2befcf826680c70ac59295c06004dd6221cf..2fecf854fe6d87cfef34678f1bc9c864ea834cb4 100644 (file)
--- a/path.c
+++ b/path.c
@@ -33,11 +33,10 @@ static struct strbuf *get_pathname(void)
        return sb;
 }
 
-static char *cleanup_path(char *path)
+static const char *cleanup_path(const char *path)
 {
        /* Clean it up */
-       if (!memcmp(path, "./", 2)) {
-               path += 2;
+       if (skip_prefix(path, "./", &path)) {
                while (*path == '/')
                        path++;
        }
@@ -46,7 +45,7 @@ static char *cleanup_path(char *path)
 
 static void strbuf_cleanup_path(struct strbuf *sb)
 {
-       char *path = cleanup_path(sb->buf);
+       const char *path = cleanup_path(sb->buf);
        if (path > sb->buf)
                strbuf_remove(sb, 0, path - sb->buf);
 }
@@ -63,7 +62,7 @@ char *mksnpath(char *buf, size_t n, const char *fmt, ...)
                strlcpy(buf, bad_path, n);
                return buf;
        }
-       return cleanup_path(buf);
+       return (char *)cleanup_path(buf);
 }
 
 static int dir_prefix(const char *buf, const char *dir)