linux-kernel - Re: [PATCH for-v5.15.x] mm/damon/dbgfs: fix 'struct pid' leaks in 'dbgfs_target_ids

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Date:   Mon, 3 Jan 2022 10:46:08 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     SeongJae Park <sj@...nel.org>
Cc:     stable@...r.kernel.org, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH for-v5.15.x] mm/damon/dbgfs: fix 'struct pid' leaks in
 'dbgfs_target_ids_write()'

On Sun, Jan 02, 2022 at 11:21:41AM +0000, SeongJae Park wrote:
> commit ebb3f994dd92f8fb4d70c7541091216c1e10cb71 upstream.
> 
> DAMON debugfs interface increases the reference counts of 'struct pid's
> for targets from the 'target_ids' file write callback
> ('dbgfs_target_ids_write()'), but decreases the counts only in DAMON
> monitoring termination callback ('dbgfs_before_terminate()').
> 
> Therefore, when 'target_ids' file is repeatedly written without DAMON
> monitoring start/termination, the reference count is not decreased and
> therefore memory for the 'struct pid' cannot be freed.  This commit
> fixes this issue by decreasing the reference counts when 'target_ids' is
> written.
> 
> Link: https://lkml.kernel.org/r/20211229124029.23348-1-sj@kernel.org
> Fixes: 4bc05954d007 ("mm/damon: implement a debugfs-based user space interface")
> Signed-off-by: SeongJae Park <sj@...nel.org>
> Cc: <stable@...r.kernel.org> # 5.15.x
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> ---
> This is a backport of a DAMON fix that merged in the mainline, for
> v5.15.x stable series.

Now queued up, thanks.

greg k-h