diff mbox series

ocfs2: fix snprintf() checking

Message ID YJovRPdOiaU6I+JK@mwanda (mailing list archive)
State New
Headers show
Series ocfs2: fix snprintf() checking | expand

Commit Message

Dan Carpenter May 11, 2021, 7:16 a.m. UTC
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(-)

Comments

Joseph Qi May 11, 2021, 12:54 p.m. UTC | #1
On 5/11/21 3:16 PM, Dan Carpenter wrote:
> 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>

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 <joseph.qi@linux.alibaba.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);
>
Dan Carpenter May 11, 2021, 1:52 p.m. UTC | #2
On Tue, May 11, 2021 at 08:54:53PM +0800, Joseph Qi wrote:
> 
> 
> On 5/11/21 3:16 PM, Dan Carpenter wrote:
> > 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>
> 
> 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 <joseph.qi@linux.alibaba.com>
> 

Thanks!  Will do.

regards,
dan carpenter
diff mbox series

Patch

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);