lib/fs: fix memory leak in get_task_name()

asprintf() allocates memory which is not freed on the error path of
get_task_name(), thus potentially leading to memory leaks.
%m specifier on fscanf allocates memory, too, which needs to be freed by
the caller.

This reworks get_task_name() to avoid memory allocation.
- Pass a buffer and its length to the function, similarly to what
  get_command_name() does, thus avoiding to allocate memory for
  the string to be returned;
- Use snprintf() instead of asprintf();
- Use fgets() instead of fscanf() to limit string length.

Fixes: 81bfd01a4c9e ("lib: move get_task_name() from rdma")
Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

1 files changed, 13 insertions, 10 deletions

diff --git a/lib/fs.c b/lib/fs.c
index f6f5f8a0..3752931c 100644
--- a/lib/fs.c
+++ b/lib/fs.c
@@ -342,25 +342,28 @@ int get_command_name(const char *pid, char *comm, size_t len)
 	return 0;
 }
 
-char *get_task_name(pid_t pid)
+int get_task_name(pid_t pid, char *name, size_t len)
 {
-	char *comm;
+	char path[PATH_MAX];
 	FILE *f;
 
 	if (!pid)
-		return NULL;
+		return -1;
 
-	if (asprintf(&comm, "/proc/%d/comm", pid) < 0)
-		return NULL;
+	if (snprintf(path, sizeof(path), "/proc/%d/comm", pid) >= sizeof(path))
+		return -1;
 
-	f = fopen(comm, "r");
+	f = fopen(path, "r");
 	if (!f)
-		return NULL;
+		return -1;
 
-	if (fscanf(f, "%ms\n", &comm) != 1)
-		comm = NULL;
+	if (!fgets(name, len, f))
+		return -1;
+
+	/* comm ends in \n, get rid of it */
+	name[strcspn(name, "\n")] = '\0';
 
 	fclose(f);
 
-	return comm;
+	return 0;
 }