From: Karel Zak <kzak@redhat.com>
Date: Fri, 6 Jan 2023 14:58:16 +0000 (+0100)
Subject: lib/sysfs: use temporary buffer
X-Git-Tag: v2.39-rc1~193
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=35d26ae8f2a09bb18c275d7c847f2d5377d8f608;p=thirdparty%2Futil-linux.git

lib/sysfs: use temporary buffer

It seems more readable (for humans and static analyzers) and safe
to use temporary buffer than use memmove to create absolute path.

Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/lib/Makemodule.am b/lib/Makemodule.am
index e94a4c4e03..d8d54f0507 100644
--- a/lib/Makemodule.am
+++ b/lib/Makemodule.am
@@ -181,7 +181,7 @@ if HAVE_CPU_SET_T
 test_sysfs_SOURCES += lib/cpuset.c
 endif
 test_sysfs_CFLAGS = $(AM_CFLAGS) -DTEST_PROGRAM_SYSFS
-test_sysfs_LDADD = $(LDADD)
+test_sysfs_LDADD = $(LDADD) libcommon.la
 
 test_procfs_SOURCES = lib/procfs.c lib/path.c lib/fileutils.c lib/strutils.c
 if HAVE_CPU_SET_T
diff --git a/lib/sysfs.c b/lib/sysfs.c
index dd2637cdd3..92a7e290b0 100644
--- a/lib/sysfs.c
+++ b/lib/sysfs.c
@@ -17,6 +17,7 @@
 #include "all-io.h"
 #include "debug.h"
 #include "strutils.h"
+#include "buffer.h"
 
 static void sysfs_blkdev_deinit_path(struct path_cxt *pc);
 static int  sysfs_blkdev_enoent_redirect(struct path_cxt *pc, const char *path, int *dirfd);
@@ -387,25 +388,29 @@ static char *get_subsystem(char *chain, char *buf, size_t bufsz)
 char *sysfs_blkdev_get_devchain(struct path_cxt *pc, char *buf, size_t bufsz)
 {
 	/* read /sys/dev/block/<maj>:<min> symlink */
-	ssize_t sz = ul_path_readlink(pc, buf, bufsz, NULL);
-	const char *prefix;
-	size_t psz = 0;
+	ssize_t ssz;
+	size_t sz = 0;
+	struct ul_buffer tmp = UL_INIT_BUFFER;
+	const char *p;
+	char *res = NULL;
 
-	if (sz <= 0 || sz + sizeof(_PATH_SYS_DEVBLOCK "/") > bufsz)
+	ssz = ul_path_readlink(pc, buf, bufsz, NULL);
+	if (ssz <= 0)
 		return NULL;
 
-	sz++;
-	prefix = ul_path_get_prefix(pc);
-	if (prefix)
-		psz = strlen(prefix);
+	if ((p = ul_path_get_prefix(pc)))
+		ul_buffer_append_string(&tmp, p);
 
-	/* create absolute path from the link */
-	memmove(buf + psz + sizeof(_PATH_SYS_DEVBLOCK "/") - 1, buf, sz);
-	if (prefix)
-		memcpy(buf, prefix, psz);
+	ul_buffer_append_string(&tmp, _PATH_SYS_DEVBLOCK "/");
+	ul_buffer_append_data(&tmp, buf, ssz);
 
-	memcpy(buf + psz, _PATH_SYS_DEVBLOCK "/", sizeof(_PATH_SYS_DEVBLOCK "/") - 1);
-	return buf;
+	p = ul_buffer_get_data(&tmp, &sz, NULL);
+	if (p && sz < bufsz) {
+		memcpy(buf, p, sz);
+		res = buf;
+	}
+	ul_buffer_free_data(&tmp);
+	return res;
 }
 
 /*
diff --git a/meson.build b/meson.build
index 60fff5ba80..fd069c1311 100644
--- a/meson.build
+++ b/meson.build
@@ -2966,6 +2966,7 @@ exe = executable(
   'test_sysfs',
   'lib/sysfs.c',
   'lib/path.c',
+  'lib/buffer.c',
   'lib/fileutils.c',
   have_cpu_set_t ? 'lib/cpuset.c' : [],
   c_args : ['-DTEST_PROGRAM_SYSFS'],