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From: Thomas Gleixner <tglx@linutronix.de>
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To: Ammar Faizi <ammarfaizi2@gnuweeb.org>, Borislav Petkov <bp@alien8.de>
Cc: Ammar Faizi <ammarfaizi2@gnuweeb.org>, Alviro Iskandar Setiawan
 <alviro.iskandar@gnuweeb.org>, Dave Hansen <dave.hansen@linux.intel.com>,
 "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>, Tony
 Luck <tony.luck@intel.com>, Yazen Ghannam <yazen.ghannam@amd.com>, Linux
 Edac Mailing List <linux-edac@vger.kernel.org>, Linux Kernel Mailing List
 <linux-kernel@vger.kernel.org>, Stable Kernel <stable@vger.kernel.org>,
 GNU/Weeb Mailing List <gwml@vger.gnuweeb.org>, x86 Mailing List
 <x86@kernel.org>
Subject: Re: [PATCH v6 2/2] x86/MCE/AMD: Fix memory leak when
 `threshold_create_bank()` fails
In-Reply-To: <20220329104705.65256-3-ammarfaizi2@gnuweeb.org>
References: <20220329104705.65256-1-ammarfaizi2@gnuweeb.org>
 <20220329104705.65256-3-ammarfaizi2@gnuweeb.org>
Date: Sun, 03 Apr 2022 19:03:58 +0200
Message-ID: <87wng6ksjl.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
List-Id: <gwml.vger.gnuweeb.org>

On Tue, Mar 29 2022 at 17:47, Ammar Faizi wrote:

> In mce_threshold_create_device(), if threshold_create_bank() fails, the
> @bp will be leaked, because the call to mce_threshold_remove_device()
> will not free the @bp. mce_threshold_remove_device() frees
> @threshold_banks. At that point, the @bp has not been written to
> @threshold_banks, @threshold_banks is NULL, so the call is just a nop.
>
> Fix this by extracting the cleanup part into a new static function
> __threshold_remove_device(), then call it from create/remove device
> functions.

The way simpler fix is to move 

>  	}
>  	this_cpu_write(threshold_banks, bp);

before the loop. That's safe because the banks cannot yet be reached via
an MCE as the vector is not yet enabled:
  
>  	if (thresholding_irq_en)
>  		mce_threshold_vector = amd_threshold_interrupt;

Thanks,

        tglx