Commit 3f62b3ed authored by Rabin Vincent's avatar Rabin Vincent Committed by Greg Kroah-Hartman
Browse files

crypto: af_alg - fix backlog handling 

commit 7e77bdeb upstream.

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: default avatarRabin Vincent <rabin.vincent@axis.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 1cfececc

crypto/af_alg.c

+3 −0
Original line number Diff line number Diff line
@@ -449,6 +449,9 @@ void af_alg_complete(struct crypto_async_request *req, int err) 
{

	struct af_alg_completion *completion = req->data;



	if (err == -EINPROGRESS)

		return;



	completion->err = err;

	complete(&completion->completion);

}