ocfs2: fix snprintf() checking

The snprintf() function returns the number of bytes which would have been printed if the buffer was large enough. In other words it can return ">= remain" but this code assumes it returns "== remain".

The run time impact of this bug is not very severe. The next iteration through the loop would trigger a WARN() when we pass a negative limit to snprintf(). We would then return success instead of -E2BIG.

The kernel implementation of snprintf() will never return negatives so there is no need to check and I have deleted that dead code.

Fixes a860f6eb4c6a ("ocfs2: sysfile interfaces for online file check")

Signed-off-by Dan Carpenter <[email protected]>

---
 fs/ocfs2/filecheck.c | 6 +-----
 fs/ocfs2/stackglue.c | 8 ++------
 2 files changed, 3 insertions(+), 11 deletions(-)

fs/ocfs2/filecheck.c +1 -5

index 90b8d300c1ee..de56e6231af8 100644
@@ -326,11 +326,7 @@ static ssize_t ocfs2_filecheck_attr_show(struct kobject *kobj,
 		ret = snprintf(buf + total, remain, "%lu\t\t%u\t%s\n",
 			       p->fe_ino, p->fe_done,
 			       ocfs2_filecheck_error(p->fe_status));
-		if (ret < 0) {
-			total = ret;
-			break;
-		}
-		if (ret == remain) {
+		if (ret >= remain) {
 			/* snprintf() didn't fit */
 			total = -E2BIG;
 			break;

fs/ocfs2/stackglue.c +2 -6

index d50e8b8dfea4..16f1bfc407f2 100644
@@ -500,11 +500,7 @@ static ssize_t ocfs2_loaded_cluster_plugins_show(struct kobject *kobj,
 	list_for_each_entry(p, &ocfs2_stack_list, sp_list) {
 		ret = snprintf(buf, remain, "%s\n",
 			       p->sp_name);
-		if (ret < 0) {
-			total = ret;
-			break;
-		}
-		if (ret == remain) {
+		if (ret >= remain) {
 			/* snprintf() didn't fit */
 			total = -E2BIG;
 			break;

@@ -531,7 +527,7 @@ static ssize_t ocfs2_active_cluster_plugin_show(struct kobject *kobj,
 	if (active_stack) {
 		ret = snprintf(buf, PAGE_SIZE, "%s\n",
 			       active_stack->sp_name);
-		if (ret == PAGE_SIZE)
+		if (ret >= PAGE_SIZE)
 			ret = -E2BIG;
 	}
 	spin_unlock(&ocfs2_stack_lock);

Quoted 11 lines · Dan Carpenter

The snprintf() function returns the number of bytes which would have been printed if the buffer was large enough. In other words it can return ">= remain" but this code assumes it returns "== remain".

The run time impact of this bug is not very severe. The next iteration through the loop would trigger a WARN() when we pass a negative limit to snprintf(). We would then return success instead of -E2BIG.

The kernel implementation of snprintf() will never return negatives so there is no need to check and I have deleted that dead code.

Quoted 2 lines

Fixes a860f6eb4c6a ("ocfs2: sysfile interfaces for online file check")

Signed-off-by Dan Carpenter <[email protected]>

Looks good. But the last 2 sections are introduced by:
74ae4e104dfc ocfs2: Create stack glue sysfs files.

With 'Fixes' tag updated,

Reviewed-by Joseph Qi <[email protected]>