From: Johannes Schindelin <johannes.schindelin@xxxxxx>
Technically, the pointer difference `end - start` _could_ be negative,
and when cast to an (unsigned) `size_t` that would cause problems. In
this instance, the symptom is:
dir.c: In function 'git_url_basename':
dir.c:3087:13: error: 'memchr' specified bound [9223372036854775808, 0]
exceeds maximum object size 9223372036854775807
[-Werror=stringop-overread]
CC ewah/bitmap.o
3087 | if (memchr(start, '/', end - start) == NULL
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
While it is a bit far-fetched to think that `end` (which is defined as
`repo + strlen(repo)`) and `start` (which starts at `repo` and never
steps beyond the NUL terminator) could result in such a negative
difference, GCC has no way of knowing that.
See also https://gcc.gnu.org/bugzilla//show_bug.cgi?id=85783.
Let's just add a safety check, primarily for GCC's benefit.
Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx>
---
dir.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/dir.c b/dir.c
index 5aa6fbad0b7..ea78f606230 100644
--- a/dir.c
+++ b/dir.c
@@ -3076,6 +3076,15 @@ char *git_url_basename(const char *repo, int is_bundle, int is_bare)
end--;
}
+ /*
+ * It should not be possible to overflow `ptrdiff_t` by passing in an
+ * insanely long URL, but GCC does not know that and will complain
+ * without this check.
+ */
+ if (end - start < 0)
+ die(_("No directory name could be guessed.\n"
+ "Please specify a directory on the command line"));
+
/*
* Strip trailing port number if we've got only a
* hostname (that is, there is no dir separator but a
--
gitgitgadget
