[PATCH] mmap error handling

I have reviewed all occurrences of mmap() in git and fixed three types
of errors/defects:

1) The result is not checked.
2) The file descriptor is closed if mmap() succeeds, but not when it
fails.
3) Various casts applied to -1 are used instead of MAP_FAILED, which is
specifically defined to check mmap() return value.

[jc: This is a second round of Pavel's patch.  He fixed up the problem
that close() potentially clobbering the errno from mmap, which
the first round had.]

Signed-off-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff.c

@@ -377,8 +377,10 @@ int diff_populate_filespec(struct diff_filespec *s, int size_only)
 		if (fd < 0)
 			goto err_empty;
 		s->data = mmap(NULL, s->size, PROT_READ, MAP_PRIVATE, fd, 0);
-		s->should_munmap = 1;
 		close(fd);
+		if (s->data == MAP_FAILED)
+			goto err_empty;
+		s->should_munmap = 1;
 	}
 	else {
 		char type[20];

diffcore-order.c

@@ -28,7 +28,7 @@ static void prepare_order(const char *orderfile)
 	}
 	map = mmap(NULL, st.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
 	close(fd);
-	if (-1 == (int)(long)map)
+	if (map == MAP_FAILED)
 		return;
 	endp = map + st.st_size;
 	for (pass = 0; pass < 2; pass++) {

local-pull.c

@@ -54,7 +54,7 @@ int fetch(unsigned char *sha1)
 		}
 		map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, ifd, 0);
 		close(ifd);
-		if (-1 == (int)(long)map) {
+		if (map == MAP_FAILED) {
 			fprintf(stderr, "cannot mmap %s\n", filename);
 			return -1;
 		}

read-cache.c

@@ -392,7 +392,7 @@ int read_cache(void)
 		return (errno == ENOENT) ? 0 : error("open failed");
 
 	size = 0; // avoid gcc warning
-	map = (void *)-1;
+	map = MAP_FAILED;
 	if (!fstat(fd, &st)) {
 		size = st.st_size;
 		errno = EINVAL;
@@ -400,7 +400,7 @@ int read_cache(void)
 			map = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 	}
 	close(fd);
-	if (-1 == (int)(long)map)
+	if (map == MAP_FAILED)
 		return error("mmap failed");
 
 	hdr = map;

rev-cache.c

@@ -212,11 +212,9 @@ int read_rev_cache(const char *path, FILE *dumpfile, int dry_run)
 		return -1;
 	}
 	map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
-	if (map == MAP_FAILED) {
 	close(fd);
+	if (map == MAP_FAILED)
 		return -1;
-	}
-	close(fd);
 
 	memset(last_sha1, 0, 20);
 	ofs = 0;

sha1_file.c

@@ -518,7 +518,7 @@ static void *map_sha1_file_internal(const unsigned char *sha1,
 	}
 	map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 	close(fd);
-	if (-1 == (int)(long)map)
+	if (map == MAP_FAILED)
 		return NULL;
 	*size = st.st_size;
 	return map;
@@ -1363,7 +1363,7 @@ int index_fd(unsigned char *sha1, int fd, struct stat *st, int write_object, con
 	if (size)
 		buf = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 	close(fd);
-	if ((int)(long)buf == -1)
+	if (buf == MAP_FAILED)
 		return -1;
 
 	if (!type)

test-delta.c

@@ -41,6 +41,7 @@ int main(int argc, char *argv[])
 	from_buf = mmap(NULL, from_size, PROT_READ, MAP_PRIVATE, fd, 0);
 	if (from_buf == MAP_FAILED) {
 		perror(argv[2]);
+		close(fd);
 		return 1;
 	}
 	close(fd);
@@ -54,6 +55,7 @@ int main(int argc, char *argv[])
 	data_buf = mmap(NULL, data_size, PROT_READ, MAP_PRIVATE, fd, 0);
 	if (data_buf == MAP_FAILED) {
 		perror(argv[3]);
+		close(fd);
 		return 1;
 	}
 	close(fd);

tools/mailsplit.c

@@ -116,8 +116,9 @@ int main(int argc, char **argv)
 	}
 	size = st.st_size;
 	map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
-	if (-1 == (int)(long)map) {
+	if (map == MAP_FAILED) {
 		perror("mmap");
+		close(fd);
 		exit(1);
 	}
 	close(fd);