* [PATCH] tracing: Correct the refcount for hist/hist_debug file if single_open() fails
@ 2025-03-13 10:37 Tengda Wu
2025-03-13 14:44 ` Steven Rostedt
0 siblings, 1 reply; 3+ messages in thread
From: Tengda Wu @ 2025-03-13 10:37 UTC (permalink / raw)
To: Steven Rostedt, Masami Hiramatsu
Cc: Mathieu Desnoyers, Zheng Yejian, linux-trace-kernel, linux-kernel
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);
+ }
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 = {
--
2.34.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] tracing: Correct the refcount for hist/hist_debug file if single_open() fails
2025-03-13 10:37 [PATCH] tracing: Correct the refcount for hist/hist_debug file if single_open() fails Tengda Wu
@ 2025-03-13 14:44 ` Steven Rostedt
2025-03-14 0:57 ` Tengda Wu
0 siblings, 1 reply; 3+ messages in thread
From: Steven Rostedt @ 2025-03-13 14:44 UTC (permalink / raw)
To: Tengda Wu
Cc: Masami Hiramatsu, Mathieu Desnoyers, Zheng Yejian,
linux-trace-kernel, linux-kernel
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 = {
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] tracing: Correct the refcount for hist/hist_debug file if single_open() fails
2025-03-13 14:44 ` Steven Rostedt
@ 2025-03-14 0:57 ` Tengda Wu
0 siblings, 0 replies; 3+ messages in thread
From: Tengda Wu @ 2025-03-14 0:57 UTC (permalink / raw)
To: Steven Rostedt
Cc: Masami Hiramatsu, Mathieu Desnoyers, Zheng Yejian,
linux-trace-kernel, linux-kernel
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 = {
^ permalink raw reply [flat|nested] 3+ messages in thread
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2025-03-13 10:37 [PATCH] tracing: Correct the refcount for hist/hist_debug file if single_open() fails Tengda Wu
2025-03-13 14:44 ` Steven Rostedt
2025-03-14 0:57 ` Tengda Wu
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