diff mbox series

tracing: Correct the refcount for hist/hist_debug file if single_open() fails

Message ID 20250313103719.1191073-1-wutengda@huaweicloud.com (mailing list archive)
State Superseded
Headers show
Series tracing: Correct the refcount for hist/hist_debug file if single_open() fails | expand

Commit Message

Tengda Wu March 13, 2025, 10:37 a.m. UTC
The function event_{hist,hist_debug}_open() maintains the refcount of
'file->tr' and 'file' through tracing_open_file_tr(), but it does not
roll back these counts when the subsequent single_open() call fails,
leading to a refcount leak.

A very obvious case is that if the hist/hist_debug file belongs to a
certain instance, the failure of single_open() will prevent the deletion
of that instance, as it relies on the condition 'tr->ref == 1' within
__remove_instance().

Fix this by calling tracing_release_file_tr() to correct the refcount
when single_open() fails.

Fixes: 1cc111b9cddc ("tracing: Fix uaf issue when open the hist or hist_debug file")
Signed-off-by: Tengda Wu <wutengda@huaweicloud.com>
Cc: stable@vger.kernel.org # v6.7+
---
 kernel/trace/trace_events_hist.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

Comments

Steven Rostedt March 13, 2025, 2:44 p.m. UTC | #1
On Thu, 13 Mar 2025 10:37:19 +0000
Tengda Wu <wutengda@huaweicloud.com> wrote:

> The function event_{hist,hist_debug}_open() maintains the refcount of
> 'file->tr' and 'file' through tracing_open_file_tr(), but it does not
> roll back these counts when the subsequent single_open() call fails,
> leading to a refcount leak.
> 
> A very obvious case is that if the hist/hist_debug file belongs to a
> certain instance, the failure of single_open() will prevent the deletion
> of that instance, as it relies on the condition 'tr->ref == 1' within
> __remove_instance().
> 
> Fix this by calling tracing_release_file_tr() to correct the refcount
> when single_open() fails.
> 
> Fixes: 1cc111b9cddc ("tracing: Fix uaf issue when open the hist or hist_debug file")
> Signed-off-by: Tengda Wu <wutengda@huaweicloud.com>
> Cc: stable@vger.kernel.org # v6.7+
> ---
>  kernel/trace/trace_events_hist.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index ad7419e24055..900b06fa8505 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -5702,8 +5702,10 @@ static int event_hist_open(struct inode *inode, struct file *file)
>  	/* Clear private_data to avoid warning in single_open() */
>  	file->private_data = NULL;
>  	ret = single_open(file, hist_show, hist_file);
> -	if (ret)
> +	if (ret) {
>  		kfree(hist_file);
> +		tracing_release_file_tr(inode, file);
> +	}

Hmm, this function has a couple more error path exits after taking the
ref count. If this is to be fixed, let's fix it completely. Each of
those error paths need to call tracing_release_file_tr().

-- Steve


>  
>  	return ret;
>  }
> @@ -5979,7 +5981,10 @@ static int event_hist_debug_open(struct inode *inode, struct file *file)
>  
>  	/* Clear private_data to avoid warning in single_open() */
>  	file->private_data = NULL;
> -	return single_open(file, hist_debug_show, file);
> +	ret = single_open(file, hist_debug_show, file);
> +	if (ret)
> +		tracing_release_file_tr(inode, file);
> +	return ret;
>  }
>  
>  const struct file_operations event_hist_debug_fops = {
Tengda Wu March 14, 2025, 12:57 a.m. UTC | #2
Hi Steven,

On 2025/3/13 22:44, Steven Rostedt wrote:
> On Thu, 13 Mar 2025 10:37:19 +0000
> Tengda Wu <wutengda@huaweicloud.com> wrote:
> 
>> The function event_{hist,hist_debug}_open() maintains the refcount of
>> 'file->tr' and 'file' through tracing_open_file_tr(), but it does not
>> roll back these counts when the subsequent single_open() call fails,
>> leading to a refcount leak.
>>
>> A very obvious case is that if the hist/hist_debug file belongs to a
>> certain instance, the failure of single_open() will prevent the deletion
>> of that instance, as it relies on the condition 'tr->ref == 1' within
>> __remove_instance().
>>
>> Fix this by calling tracing_release_file_tr() to correct the refcount
>> when single_open() fails.
>>
>> Fixes: 1cc111b9cddc ("tracing: Fix uaf issue when open the hist or hist_debug file")
>> Signed-off-by: Tengda Wu <wutengda@huaweicloud.com>
>> Cc: stable@vger.kernel.org # v6.7+
>> ---
>>  kernel/trace/trace_events_hist.c | 9 +++++++--
>>  1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
>> index ad7419e24055..900b06fa8505 100644
>> --- a/kernel/trace/trace_events_hist.c
>> +++ b/kernel/trace/trace_events_hist.c
>> @@ -5702,8 +5702,10 @@ static int event_hist_open(struct inode *inode, struct file *file)
>>  	/* Clear private_data to avoid warning in single_open() */
>>  	file->private_data = NULL;
>>  	ret = single_open(file, hist_show, hist_file);
>> -	if (ret)
>> +	if (ret) {
>>  		kfree(hist_file);
>> +		tracing_release_file_tr(inode, file);
>> +	}
> 
> Hmm, this function has a couple more error path exits after taking the
> ref count. If this is to be fixed, let's fix it completely. Each of
> those error paths need to call tracing_release_file_tr().
> 
> -- Steve

Oops, I got it. The v2 is coming soon. Thanks a lot.

-- Tengda

> 
> 
>>  
>>  	return ret;
>>  }
>> @@ -5979,7 +5981,10 @@ static int event_hist_debug_open(struct inode *inode, struct file *file)
>>  
>>  	/* Clear private_data to avoid warning in single_open() */
>>  	file->private_data = NULL;
>> -	return single_open(file, hist_debug_show, file);
>> +	ret = single_open(file, hist_debug_show, file);
>> +	if (ret)
>> +		tracing_release_file_tr(inode, file);
>> +	return ret;
>>  }
>>  
>>  const struct file_operations event_hist_debug_fops = {
diff mbox series

Patch

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index ad7419e24055..900b06fa8505 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -5702,8 +5702,10 @@  static int event_hist_open(struct inode *inode, struct file *file)
 	/* Clear private_data to avoid warning in single_open() */
 	file->private_data = NULL;
 	ret = single_open(file, hist_show, hist_file);
-	if (ret)
+	if (ret) {
 		kfree(hist_file);
+		tracing_release_file_tr(inode, file);
+	}
 
 	return ret;
 }
@@ -5979,7 +5981,10 @@  static int event_hist_debug_open(struct inode *inode, struct file *file)
 
 	/* Clear private_data to avoid warning in single_open() */
 	file->private_data = NULL;
-	return single_open(file, hist_debug_show, file);
+	ret = single_open(file, hist_debug_show, file);
+	if (ret)
+		tracing_release_file_tr(inode, file);
+	return ret;
 }
 
 const struct file_operations event_hist_debug_fops = {