[PATCH] ocfs2: fix snprintf() checking

Dan Carpenter
2021-05-11T07:16:52Z

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 <dan.carpenter@oracle.com>
---
fs/ocfs2/filecheck.c | 6 +-----
fs/ocfs2/stackglue.c | 8 ++------
2 files changed, 3 insertions(+), 11 deletions(-)

diff --git a/fs/ocfs2/filecheck.c b/fs/ocfs2/filecheck.c
index 90b8d300c1ee..de56e6231af8 100644
--- a/fs/ocfs2/filecheck.c
+++ b/fs/ocfs2/filecheck.c
@@ -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;
diff --git a/fs/ocfs2/stackglue.c b/fs/ocfs2/stackglue.c
index d50e8b8dfea4..16f1bfc407f2 100644
--- a/fs/ocfs2/stackglue.c
+++ b/fs/ocfs2/stackglue.c
@@ -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);
--
2.30.2