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Re: kmemleak for MIPS

To: Daniel Baluta <dbaluta@ixiacom.com>
Subject: Re: kmemleak for MIPS
From: Catalin Marinas <catalin.marinas@arm.com>
Date: Wed, 30 Mar 2011 12:38:05 +0100
Cc: Maxin John <maxin.john@gmail.com>, naveen yadav <yad.naveen@gmail.com>, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Eric Dumazet <eric.dumazet@gmail.com>
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On Wed, 2011-03-30 at 12:24 +0100, Daniel Baluta wrote:
> We have:
> 
> > UDP hash table entries: 128 (order: 0, 4096 bytes)
> > CONFIG_BASE_SMALL=0
> 
> udp_table_init looks like:
> 
>         if (!CONFIG_BASE_SMALL)
>                 table->hash = alloc_large_system_hash(name, .. &table->mask);
>         /*
>          * Make sure hash table has the minimum size
>          */
> 
> Since CONFIG_BASE_SMALL is 0, we are allocating the hash using
> alloc_large_system
> Then:
>         if (CONFIG_BASE_SMALL || table->mask < UDP_HTABLE_SIZE_MIN - 1) {
>                 table->hash = kmalloc();
> 
> table->mask is 127, and UDP_HTABLE_SIZE_MIN is 256, so we are allocating again
> table->hash without freeing already allocated memory.

Indeed (on my ARM system the reported UDP hash table entries is 512, so
I don't get the memory leak).

> We could free table->hash, before allocating the memory with kmalloc.
> I don't fully understand the condition table->mask < UDP_HTABLE_SIZE_MIN - 1.

We don't have the equivalent of free_large_system_hash(). Reordering the
'if' blocks may be better.

-- 
Catalin



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