From: "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: Johannes Schindelin <johannes.schindelin@gmx.de>,
Johannes Schindelin <johannes.schindelin@gmx.de>
Subject: [PATCH 4/4] dir.c: avoid "exceeds maximum object size" error with GCC v12.x
Date: Tue, 24 May 2022 00:23:06 +0000 [thread overview]
Message-ID: <365889ee96e37dc9dcbe60d98880eb256dae90ee.1653351786.git.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.1238.git.1653351786.gitgitgadget@gmail.com>
From: Johannes Schindelin <johannes.schindelin@gmx.de>
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@gmx.de>
---
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
next prev parent reply other threads:[~2022-05-24 0:24 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-24 0:23 [PATCH 0/4] ci: fix windows-build with GCC v12.x Johannes Schindelin via GitGitGadget
2022-05-24 0:23 ` [PATCH 1/4] compat/win32/syslog: fix use-after-realloc Johannes Schindelin via GitGitGadget
2022-05-24 12:39 ` Johannes Schindelin
2022-05-24 20:58 ` Junio C Hamano
2022-05-24 0:23 ` [PATCH 2/4] nedmalloc: avoid new compile error Johannes Schindelin via GitGitGadget
2022-05-24 8:00 ` Ævar Arnfjörð Bjarmason
2022-05-24 15:59 ` René Scharfe
2022-05-24 20:46 ` Johannes Schindelin
2022-05-24 21:33 ` Ævar Arnfjörð Bjarmason
2022-05-24 0:23 ` [PATCH 3/4] http.c: avoid danging pointer to local variable `finished` Johannes Schindelin via GitGitGadget
2022-05-24 7:58 ` Ævar Arnfjörð Bjarmason
2022-05-24 20:06 ` Junio C Hamano
2022-05-24 21:15 ` Johannes Schindelin
2022-05-24 21:45 ` Ævar Arnfjörð Bjarmason
2022-05-24 22:38 ` Junio C Hamano
2022-05-25 10:16 ` Johannes Schindelin
2022-05-25 12:48 ` Ævar Arnfjörð Bjarmason
2022-05-24 0:23 ` Johannes Schindelin via GitGitGadget [this message]
2022-05-24 5:53 ` [PATCH 4/4] dir.c: avoid "exceeds maximum object size" error with GCC v12.x Ævar Arnfjörð Bjarmason
2022-05-24 21:05 ` Johannes Schindelin
2022-05-25 13:39 ` Derrick Stolee
2022-05-25 18:27 ` Junio C Hamano
2022-05-24 15:54 ` [PATCH 0/4] ci: fix windows-build " Jeff Hostetler
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