libtrace: Fix memory leak in tracefs_cpu

Commit Message

Kutzer, Philipp March 17, 2025, 11:24 a.m. UTC

From: Philipp Kutzer <[e-mail]>

Hi,

with the introduction of the interface to allow the tracefs_cpu to handle buffer allocation on their
 own a memory leak was built in. 
(Commit 1e1cc549d7e7fa408081e03e4effd3591a131ae5 - libtracefs: Add API to read tracefs_cpu 
and return a kbuffer)

We cyclically call the tracefs_iterate_raw_events function from one of our applications and 
noticed that our application was increasingly allocating memory. 

With the help of Address Sanitizer the root cause, allocating but not freeing memory 
for "tcpu->buffer" was found. The fix will free memory during close and cleanup function 
and has been successfully tested in our environment. The original problem (memory leak) 
has been resolved.

Signed-off-by: Philipp Kutzer mailto:[e-mail]
---

Comments

Steven Rostedt April 3, 2025, 7:14 p.m. UTC | #1

On Mon, 17 Mar 2025 11:24:36 +0000
"Kutzer, Philipp" <[e-mail]> wrote:

> From: Philipp Kutzer <[e-mail]>
> 
> Hi,
> 
> with the introduction of the interface to allow the tracefs_cpu to handle buffer allocation on their
>  own a memory leak was built in. 
> (Commit 1e1cc549d7e7fa408081e03e4effd3591a131ae5 - libtracefs: Add API to read tracefs_cpu 
> and return a kbuffer)
> 
> We cyclically call the tracefs_iterate_raw_events function from one of our applications and 
> noticed that our application was increasingly allocating memory. 
> 
> With the help of Address Sanitizer the root cause, allocating but not freeing memory 
> for "tcpu->buffer" was found. The fix will free memory during close and cleanup function 
> and has been successfully tested in our environment. The original problem (memory leak) 
> has been resolved.

Note, I cleaned up the change log:

    libtrace: Fix memory leak in tracefs_cpu
    
    The introduction of the interface to allow the tracefs_cpu to handle buffer
    allocation on their own caused a memory leak.  (Commit 1e1cc549d7
    ("libtracefs: Add API to read tracefs_cpu and return a kbuffer")).
    
    The help of Address Sanitizer found the root cause. The "tcpu->buffer" was
    being allocated but not freed. The fix will free memory during close and
    cleanup functions.


> 
> Signed-off-by: Philipp Kutzer mailto:[e-mail]

Also, this should be:

 Signed-off-by: Philipp Kutzer <[e-mail]>

> ---
> 
> diff --git a/src/tracefs-record.c b/src/tracefs-record.c
> index a2dcfc2..4cd0917 100644
> --- a/src/tracefs-record.c
> +++ b/src/tracefs-record.c
> @@ -293,6 +293,8 @@ void tracefs_cpu_close(struct tracefs_cpu *tcpu)
>         if (!tcpu)
>                 return;
> 
> +       free(tcpu->buffer);
> +       tcpu->buffer = NULL;
>         close(tcpu->fd);
>         tracefs_cpu_free_fd(tcpu);
> }

This also had whitespace issues.

I fixed it up and applied it.

Thanks,

-- Steve

Patch

diff --git a/src/tracefs-record.c b/src/tracefs-record.c
index a2dcfc2..4cd0917 100644
--- a/src/tracefs-record.c
+++ b/src/tracefs-record.c
@@ -293,6 +293,8 @@  void tracefs_cpu_close(struct tracefs_cpu *tcpu)
        if (!tcpu)
                return;

+       free(tcpu->buffer);
+       tcpu->buffer = NULL;
        close(tcpu->fd);
        tracefs_cpu_free_fd(tcpu);
}