[PATCH] objtool: rework error handling in objtool_create_backup

[PATCH] objtool: rework error handling in objtool_create_backup

[Tom Rix]

The cppcheck reports this issue
[tools/objtool/objtool.c:65]: (error) Memory leak: name

This is a general problem.  When ojbtool_create_backup() fails anywhere it
returns an error without freeing any of the buffers it allocates.  So
rework the error handler to goto the appropriate free level when an error
occurs.

Fixes: 8ad15c690084 ("objtool: Add --backup")
Signed-off-by: Tom Rix <trix@redhat.com>
---
 tools/objtool/objtool.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c
index 512669ce064c..2fd10804e7a7 100644
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -25,6 +25,7 @@ static bool objtool_create_backup(const char *_objname)
 {
 	int len = strlen(_objname);
 	char *buf, *base, *name = malloc(len+6);
+	bool ret = false;
 	int s, d, l, t;
 
 	if (!name) {
@@ -38,19 +39,19 @@ static bool objtool_create_backup(const char *_objname)
 	d = open(name, O_CREAT|O_WRONLY|O_TRUNC, 0644);
 	if (d < 0) {
 		perror("failed to create backup file");
-		return false;
+		goto err1;
 	}
 
 	s = open(_objname, O_RDONLY);
 	if (s < 0) {
 		perror("failed to open orig file");
-		return false;
+		goto err2;
 	}
 
 	buf = malloc(4096);
 	if (!buf) {
 		perror("failed backup data malloc");
-		return false;
+		goto err3;
 	}
 
 	while ((l = read(s, buf, 4096)) > 0) {
@@ -59,7 +60,7 @@ static bool objtool_create_backup(const char *_objname)
 			t = write(d, base, l);
 			if (t < 0) {
 				perror("failed backup write");
-				return false;
+				goto err4;
 			}
 			base += t;
 			l -= t;
@@ -68,15 +69,21 @@ static bool objtool_create_backup(const char *_objname)
 
 	if (l < 0) {
 		perror("failed backup read");
-		return false;
+		goto err4;
 	}
 
-	free(name);
+	ret = true;
+
+err4:
 	free(buf);
-	close(d);
+err3:
 	close(s);
+err2:
+	close(d);
+err1:
+	free(name);
 
-	return true;
+	return ret;
 }
 
 struct objtool_file *objtool_open_read(const char *_objname)
-- 
2.27.0

Re: [PATCH] objtool: rework error handling in objtool_create_backup

[Peter Zijlstra]

On Sat, Apr 30, 2022 at 01:32:40PM -0400, Tom Rix wrote:
> The cppcheck reports this issue
> [tools/objtool/objtool.c:65]: (error) Memory leak: name
> 
> This is a general problem.  When ojbtool_create_backup() fails anywhere it
> returns an error without freeing any of the buffers it allocates.  So
> rework the error handler to goto the appropriate free level when an error
> occurs.

If it fails, objtool terminates. Process termination releases all
resources.