linux-kernel - Re: [PATCH] MIPS: pgalloc: fix memory leak caused by pgd

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Message-ID: <20220314145108.GB13438@alpha.franken.de>
Date:   Mon, 14 Mar 2022 15:51:08 +0100
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     yaliang.wang@...driver.com
Cc:     rppt@...nel.org, huangpei@...ngson.cn, akpm@...ux-foundation.org,
        kumba@...too.org, geert@...ux-m68k.org, anshuman.khandual@....com,
        penberg@...nel.org, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MIPS: pgalloc: fix memory leak caused by pgd_free()

On Thu, Mar 10, 2022 at 07:31:16PM +0800, yaliang.wang@...driver.com wrote:
> From: Yaliang Wang <Yaliang.Wang@...driver.com>
> 
> pgd page is freed by generic implementation pgd_free() since commit
> f9cb654cb550 ("asm-generic: pgalloc: provide generic pgd_free()"),
> however, there are scenarios that the system uses more than one page as
> the pgd table, in such cases the generic implementation pgd_free() won't
> be applicable anymore. For example, when PAGE_SIZE_4KB is enabled and
> MIPS_VA_BITS_48 is not enabled in a 64bit system, the macro "PGD_ORDER"
> will be set as "1", which will cause allocating two pages as the pgd
> table. Well, at the same time, the generic implementation pgd_free()
> just free one pgd page, which will result in the memory leak.
> 
> The memory leak can be easily detected by executing shell command:
> "while true; do ls > /dev/null; grep MemFree /proc/meminfo; done"
> 
> Fixes: f9cb654cb550 ("asm-generic: pgalloc: provide generic pgd_free()")
> Signed-off-by: Yaliang Wang <Yaliang.Wang@...driver.com>
> ---
>  arch/mips/include/asm/pgalloc.h | 6 ++++++
>  1 file changed, 6 insertions(+)

applied to mips-next.

Thomas.

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