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List:       linux-crypto-vger
Subject:    Re: [PATCH] crypto: af_alg: fix backlog handling
From:       Herbert Xu <herbert () gondor ! apana ! org ! au>
Date:       2014-12-22 11:55:29
Message-ID: 20141222115529.GC19532 () gondor ! apana ! org ! au
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On Fri, Dec 19, 2014 at 01:36:08PM +0100, Rabin Vincent wrote:
> If a request is backlogged, it's complete() handler will get called
> twice: once with -EINPROGRESS, and once with the final error code.
> 
> af_alg's complete handler, unlike other users, does not handle the
> -EINPROGRESS but instead always completes the completion that recvmsg()
> is waiting on.  This can lead to a return to user space while the
> request is still pending in the driver.  If userspace closes the sockets
> before the requests are handled by the driver, this will lead to
> use-after-frees (and potential crashes) in the kernel due to the tfm
> having been freed.
> 
> The crashes can be easily reproduced (for example) by reducing the max
> queue length in cryptod.c and running the following (from
> http://www.chronox.de/libkcapi.html) on AES-NI capable hardware:
> 
>  $ while true; do kcapi -x 1 -e -c '__ecb-aes-aesni' \
>     -k 00000000000000000000000000000000 \
>     -p 00000000000000000000000000000000 >/dev/null & done
> 
> Signed-off-by: Rabin Vincent <rabin.vincent@axis.com>

Patch applied to crypto.  Thanks!
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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