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Date: Tue, 15 Jul 2014 15:12:19 +0900
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Andrey Ryabinin <a.ryabinin@samsung.com>
Cc: linux-kernel@vger.kernel.org, Dmitry Vyukov <dvyukov@google.com>,
        Konstantin Serebryany <kcc@google.com>,
        Alexey Preobrazhensky <preobr@google.com>,
        Andrey Konovalov <adech.fo@gmail.com>,
        Yuri Gribov <tetra2005@gmail.com>,
        Konstantin Khlebnikov <koct9i@gmail.com>,
        Sasha Levin <sasha.levin@oracle.com>, Michal Marek <mmarek@suse.cz>,
        Russell King <linux@arm.linux.org.uk>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
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        linux-kbuild@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        x86@kernel.org, linux-mm@kvack.org
Subject: Re: [RFC/PATCH RESEND -next 20/21] fs: dcache: manually unpoison
 dname after allocation to shut up kasan's reports
Message-ID: <20140715061219.GK11317@js1304-P5Q-DELUXE>
References: <1404905415-9046-1-git-send-email-a.ryabinin@samsung.com>
 <1404905415-9046-21-git-send-email-a.ryabinin@samsung.com>
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On Wed, Jul 09, 2014 at 03:30:14PM +0400, Andrey Ryabinin wrote:
> We need to manually unpoison rounded up allocation size for dname
> to avoid kasan's reports in __d_lookup_rcu.
> __d_lookup_rcu may validly read a little beyound allocated size.

If it read a little beyond allocated size, IMHO, it is better to
allocate correct size.

kmalloc(name->len + 1, GFP_KERNEL); -->
kmalloc(roundup(name->len + 1, sizeof(unsigned long ), GFP_KERNEL);

Isn't it?

Thanks.

> 
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
> ---
>  fs/dcache.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/dcache.c b/fs/dcache.c
> index b7e8b20..dff64f2 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -38,6 +38,7 @@
>  #include <linux/prefetch.h>
>  #include <linux/ratelimit.h>
>  #include <linux/list_lru.h>
> +#include <linux/kasan.h>
>  #include "internal.h"
>  #include "mount.h"
>  
> @@ -1412,6 +1413,8 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
>  			kmem_cache_free(dentry_cache, dentry); 
>  			return NULL;
>  		}
> +		unpoison_shadow(dname,
> +				roundup(name->len + 1, sizeof(unsigned long)));
>  	} else  {
>  		dname = dentry->d_iname;
>  	}	
> -- 
> 1.8.5.5
> 
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