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From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>,
	git@vger.kernel.org,
	"Johannes Schindelin" <johannes.schindelin@gmx.de>,
	"Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>
Subject: [PATCH 3/3] untracked-cache: simplify parsing by dropping "len"
Date: Thu, 18 Apr 2019 17:18:35 -0400	[thread overview]
Message-ID: <20190418211835.GC18520@sigill.intra.peff.net> (raw)
In-Reply-To: <20190418211408.GA18011@sigill.intra.peff.net>

The code which parses untracked-cache extensions from disk keeps a "len"
variable, which is the size of the string we are parsing. But since we
now have an "end of string" variable, we can just use that to get the
length when we need it. This eliminates the need to keep "len" up to
date (and removes the possibility of any errors where "len" and "eos"
get out of sync).

As a bonus, it means we are not storing a string length in an "int",
which is a potential source of overflows (though in this case it seems
fairly unlikely for that to cause any memory problems).

Signed-off-by: Jeff King <peff@peff.net>
---
 dir.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/dir.c b/dir.c
index 17865f44df..60438b2cdc 100644
--- a/dir.c
+++ b/dir.c
@@ -2735,7 +2735,7 @@ static int read_one_dir(struct untracked_cache_dir **untracked_,
 	const unsigned char *data = rd->data, *end = rd->end;
 	const unsigned char *eos;
 	unsigned int value;
-	int i, len;
+	int i;
 
 	memset(&ud, 0, sizeof(ud));
 
@@ -2756,28 +2756,25 @@ static int read_one_dir(struct untracked_cache_dir **untracked_,
 	eos = memchr(data, '\0', end - data);
 	if (!eos || eos == end)
 		return -1;
-	len = eos - data;
 
-	*untracked_ = untracked = xmalloc(st_add3(sizeof(*untracked), len, 1));
+	*untracked_ = untracked = xmalloc(st_add3(sizeof(*untracked), eos - data, 1));
 	memcpy(untracked, &ud, sizeof(ud));
-	memcpy(untracked->name, data, len + 1);
+	memcpy(untracked->name, data, eos - data + 1);
 	data = eos + 1;
 
 	for (i = 0; i < untracked->untracked_nr; i++) {
 		eos = memchr(data, '\0', end - data);
 		if (!eos || eos == end)
 			return -1;
-		len = eos - data;
-		untracked->untracked[i] = xmemdupz(data, len);
+		untracked->untracked[i] = xmemdupz(data, eos - data);
 		data = eos + 1;
 	}
 
 	rd->ucd[rd->index++] = untracked;
 	rd->data = data;
 
 	for (i = 0; i < untracked->dirs_nr; i++) {
-		len = read_one_dir(untracked->dirs + i, rd);
-		if (len < 0)
+		if (read_one_dir(untracked->dirs + i, rd) < 0)
 			return -1;
 	}
 	return 0;
-- 
@@ -2735,7 +2735,7 @@ static int read_one_dir(struct untracked_cache_dir **untracked_,
 	const unsigned char *data = rd->data, *end = rd->end;
 	const unsigned char *eos;
 	unsigned int value;
-	int i, len;
+	int i;
 
 	memset(&ud, 0, sizeof(ud));
 
@@ -2756,28 +2756,25 @@ static int read_one_dir(struct untracked_cache_dir **untracked_,
 	eos = memchr(data, '\0', end - data);
 	if (!eos || eos == end)
 		return -1;
-	len = eos - data;
 
-	*untracked_ = untracked = xmalloc(st_add3(sizeof(*untracked), len, 1));
+	*untracked_ = untracked = xmalloc(st_add3(sizeof(*untracked), eos - data, 1));
 	memcpy(untracked, &ud, sizeof(ud));
-	memcpy(untracked->name, data, len + 1);
+	memcpy(untracked->name, data, eos - data + 1);
 	data = eos + 1;
 
 	for (i = 0; i < untracked->untracked_nr; i++) {
 		eos = memchr(data, '\0', end - data);
 		if (!eos || eos == end)
 			return -1;
-		len = eos - data;
-		untracked->untracked[i] = xmemdupz(data, len);
+		untracked->untracked[i] = xmemdupz(data, eos - data);
 		data = eos + 1;
 	}
 
 	rd->ucd[rd->index++] = untracked;
 	rd->data = data;
 
 	for (i = 0; i < untracked->dirs_nr; i++) {
-		len = read_one_dir(untracked->dirs + i, rd);
-		if (len < 0)
+		if (read_one_dir(untracked->dirs + i, rd) < 0)
 			return -1;
 	}
 	return 0;
-- 
2.21.0.1092.g8b0302e9c4

  parent reply	other threads:[~2019-04-18 21:18 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-10 12:56 [PATCH 0/1] Fix an off-by-one bug in the untracked cache code Johannes Schindelin via GitGitGadget
2019-04-10 12:56 ` [PATCH 1/1] untracked cache: fix off-by-one Johannes Schindelin via GitGitGadget
2019-04-10 16:20   ` Jeff King
2019-04-12  1:48     ` Junio C Hamano
2019-04-18 21:14       ` [PATCH 0/3] untracked cache parsing fixups Jeff King
2019-04-18 21:17         ` [PATCH 1/3] untracked-cache: be defensive about missing NULs in index Jeff King
2019-04-19  5:29           ` Junio C Hamano
2019-04-18 21:17         ` [PATCH 2/3] untracked-cache: simplify parsing by dropping "next" Jeff King
2019-04-19  5:33           ` Junio C Hamano
2019-04-18 21:18         ` Jeff King [this message]
2019-04-18 21:24         ` [PATCH 4/3] untracked-cache: use FLEX_ALLOC to create internal structs Jeff King
2019-04-19  9:18           ` Duy Nguyen
2019-04-19 19:43             ` Jeff King

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