netdev - Re: [PATCH 4/8] rhashtable: fix race in nested_table

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Message-ID: <20180505092907.2qa3scf6bzvubmtt@gondor.apana.org.au>
Date:   Sat, 5 May 2018 17:29:07 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     NeilBrown <neilb@...e.com>
Cc:     Thomas Graf <tgraf@...g.ch>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/8] rhashtable: fix race in nested_table_alloc()

On Fri, May 04, 2018 at 01:54:14PM +1000, NeilBrown wrote:
> If two threads run nested_table_alloc() at the same time
> they could both allocate a new table.
> Best case is that one of them will never be freed, leaking memory.
> Worst case is hat entry get stored there before it leaks,
> and the are lost from the table.
> 
> So use cmpxchg to detect the race and free the unused table.
> 
> Fixes: da20420f83ea ("rhashtable: Add nested tables")
> Cc: stable@...r.kernel.org # 4.11+
> Signed-off-by: NeilBrown <neilb@...e.com>

What about the spinlock that's meant to be held around this
operation?

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt