From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: git@vger.kernel.org
Cc: "Junio C Hamano" <gitster@pobox.com>,
"René Scharfe" <l.s.r@web.de>, "Jinoh Kang" <luke1337@theori.io>,
"Phillip Wood" <phillip.wood@talktalk.net>,
"Glen Choo" <chooglen@google.com>,
"Paul Tan" <pyokagan@gmail.com>,
"Han-Wen Nienhuys" <hanwen@google.com>,
"Karthik Nayak" <karthik.188@gmail.com>,
"Jeff Smith" <whydoubt@gmail.com>,
"Taylor Blau" <me@ttaylorr.com>,
"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: [RFC PATCH 08/15] strbuf.c: use st_add3(), not unsigned_add_overflows()
Date: Fri, 3 Jun 2022 20:37:45 +0200 [thread overview]
Message-ID: <RFC-patch-08.15-2c4b7832144-20220603T183608Z-avarab@gmail.com> (raw)
In-Reply-To: <RFC-cover-00.15-00000000000-20220603T183608Z-avarab@gmail.com>
Change the strbuf_grow() function to use st_add3() instead of doing
its own unsigned_add_overflows() checks. The overflow checking here
was originally added in b449f4cfc97 (Rework strbuf API and semantics.,
2007-09-06) and adjusted in 1368f65002b (compat: helper for detecting
unsigned overflow, 2010-10-10). Instead we compute a "sz" with
st_add3().
That was done at a time when the underlying xrealloc() in
git-compat-util.h didn't use st_mult() yet, that has been the case
since the later e7792a74bcf (harden REALLOC_ARRAY and xcalloc against
size_t overflow, 2016-02-22).
The only behavior change here should be the very obscure edge case
that we'd previously die() in cases where we strictly didn't need to,
as we'd check both "extra + 1" and "sb->len + extra + 1" for
overflow. If we overflowed only on the latter but were doing the
former we'd needlessly die() die. I don't think that difference
mattered, but it's noted here for completeness.
While we're at it add an inline comment about why we're adding 1 to
the values, that's also explained in the API documentation in
strbuf.h, but since we're using that magic constant here...
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
strbuf.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/strbuf.c b/strbuf.c
index 61c4630aeeb..f0a74d2bfb1 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -91,12 +91,12 @@ void strbuf_attach(struct strbuf *sb, void *buf, size_t len, size_t alloc)
void strbuf_grow(struct strbuf *sb, size_t extra)
{
int new_buf = !sb->alloc;
- if (unsigned_add_overflows(extra, 1) ||
- unsigned_add_overflows(sb->len, extra + 1))
- die("you want to use way too much memory");
+ const size_t sz_buf = new_buf ? 0 : sb->len;
+ const size_t sz = st_add3(sz_buf, extra, 1 /* for \0 */);
+
if (new_buf)
sb->buf = NULL;
- ALLOC_GROW(sb->buf, sb->len + extra + 1, sb->alloc);
+ ALLOC_GROW(sb->buf, sz, sb->alloc);
if (new_buf && !sb->buf)
BUG("for a new buffer ALLOC_GROW() should always do work!");
if (new_buf)
--
2.36.1.1124.g577fa9c2ebd
next prev parent reply other threads:[~2022-06-03 18:39 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-03 18:37 [RFC PATCH 00/15] Fix GCC -fanalyzer warnings & add -fanalyzer DEVOPTS mode Ævar Arnfjörð Bjarmason
2022-06-03 18:37 ` [RFC PATCH 01/15] remote.c: don't dereference NULL in freeing loop Ævar Arnfjörð Bjarmason
2022-06-03 21:07 ` René Scharfe
2022-06-03 21:28 ` Junio C Hamano
2022-06-03 22:32 ` Glen Choo
2022-06-04 12:51 ` Phillip Wood
2022-06-04 16:20 ` Ævar Arnfjörð Bjarmason
2022-06-03 18:37 ` [RFC PATCH 02/15] pull.c: don't feed NULL to strcmp() on get_rebase_fork_point() path Ævar Arnfjörð Bjarmason
2022-06-03 21:27 ` René Scharfe
2022-06-03 18:37 ` [RFC PATCH 03/15] reftable: don't memset() a NULL from failed malloc() Ævar Arnfjörð Bjarmason
2022-06-03 22:22 ` René Scharfe
2022-06-04 0:54 ` Ævar Arnfjörð Bjarmason
2022-06-04 12:24 ` René Scharfe
2022-06-04 16:23 ` Ævar Arnfjörð Bjarmason
2022-06-04 20:31 ` René Scharfe
2022-06-06 16:53 ` Junio C Hamano
2022-06-06 17:38 ` Ævar Arnfjörð Bjarmason
2022-06-06 17:44 ` Junio C Hamano
2022-06-06 17:46 ` Ævar Arnfjörð Bjarmason
2022-06-03 18:37 ` [RFC PATCH 04/15] diff-lib.c: don't dereference NULL in oneway_diff() Ævar Arnfjörð Bjarmason
2022-06-03 22:48 ` René Scharfe
2022-06-03 18:37 ` [RFC PATCH 05/15] refs/packed-backend.c: add a BUG() if iter is NULL Ævar Arnfjörð Bjarmason
2022-06-03 23:14 ` René Scharfe
2022-06-03 18:37 ` [RFC PATCH 06/15] ref-filter.c: BUG() out on show_ref() with NULL refname Ævar Arnfjörð Bjarmason
2022-06-04 18:07 ` René Scharfe
2022-06-03 18:37 ` [RFC PATCH 07/15] strbuf.c: placate -fanalyzer in strbuf_grow() Ævar Arnfjörð Bjarmason
2022-06-04 12:24 ` René Scharfe
2022-06-04 12:46 ` Phillip Wood
2022-06-04 16:21 ` Ævar Arnfjörð Bjarmason
2022-06-04 20:37 ` René Scharfe
2022-06-05 10:20 ` Phillip Wood
2022-06-03 18:37 ` Ævar Arnfjörð Bjarmason [this message]
2022-06-04 21:27 ` [RFC PATCH 08/15] strbuf.c: use st_add3(), not unsigned_add_overflows() René Scharfe
2022-06-03 18:37 ` [RFC PATCH 09/15] add-patch: assert parse_diff() expectations with BUG() Ævar Arnfjörð Bjarmason
2022-06-04 13:04 ` Phillip Wood
2022-06-03 18:37 ` [RFC PATCH 10/15] reftable: don't have reader_get_block() confuse -fanalyzer Ævar Arnfjörð Bjarmason
2022-06-03 18:37 ` [RFC PATCH 11/15] blame.c: clarify the state of "final_commit" for -fanalyzer Ævar Arnfjörð Bjarmason
2022-06-03 18:37 ` [RFC PATCH 12/15] pack.h: wrap write_*file*() functions Ævar Arnfjörð Bjarmason
2022-06-03 18:37 ` [RFC PATCH 13/15] pack-write API: pass down "verify" not arbitrary flags Ævar Arnfjörð Bjarmason
2022-06-03 18:37 ` [RFC PATCH 14/15] config.mak.dev: add a DEVOPTS=analyzer mode to use GCC's -fanalyzer Ævar Arnfjörð Bjarmason
2022-06-03 18:37 ` [RFC PATCH 15/15] config.mak.dev: add and use ASSERT_FOR_FANALYZER() macro Ævar Arnfjörð Bjarmason
2022-06-04 13:12 ` Phillip Wood
2022-06-07 15:50 ` [PATCH 0/3] remote API: fix -fanalyzer-spotted freeing issue Ævar Arnfjörð Bjarmason
2022-06-07 15:50 ` [PATCH 1/3] remote.c: remove braces from one-statement "for"-loops Ævar Arnfjörð Bjarmason
2022-06-07 15:50 ` [PATCH 2/3] remote.c: don't dereference NULL in freeing loop Ævar Arnfjörð Bjarmason
2022-06-07 17:23 ` Junio C Hamano
2022-06-07 15:50 ` [PATCH 3/3] remote API: don't buggily FREE_AND_NULL(), free() instead Ævar Arnfjörð Bjarmason
2022-06-07 17:02 ` Glen Choo
2022-06-07 18:09 ` Junio C Hamano
2022-06-07 17:29 ` Junio C Hamano
2022-06-07 17:32 ` [PATCH 0/3] remote API: fix -fanalyzer-spotted freeing issue Junio C Hamano
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