linux-kernel - Re: [PATCH 2/3] zram: do not use copy_page with non-page alinged address

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Message-ID: <20170414054105.GC462@jagdpanzerIV.localdomain>
Date:   Fri, 14 Apr 2017 14:41:05 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        kernel-team@....com, stable@...r.kernel.org
Subject: Re: [PATCH 2/3] zram: do not use copy_page with non-page alinged
 address

Hello,

On (04/13/17 09:17), Minchan Kim wrote:
> The copy_page is optimized memcpy for page-alinged address.
> If it is used with non-page aligned address, it can corrupt memory which
> means system corruption. With zram, it can happen with
> 
> 1. 64K architecture
> 2. partial IO
> 3. slub debug
> 
> Partial IO need to allocate a page and zram allocates it via kmalloc.
> With slub debug, kmalloc(PAGE_SIZE) doesn't return page-size aligned
> address. And finally, copy_page(mem, cmem) corrupts memory.

which would be the case for many other copy_page() calls in the kernel.
right? if so - should the fix be in copy_page() then?

	-ss