Re: [PATCH] crypto/authenc: don't return -EBUSY when enqueuing the hash request

Herbert Xu
2025-09-23T03:47:36Z

On Mon, Sep 22, 2025 at 09:08:42PM +0200, Mikulas Patocka wrote:
>
> When we return -EBUSY from encryption routines, the caller is supposed to
> sleep until it receives -EINPROGRESS in the callback method.
>
> However when using authenc with asynchronous hash, the hash function may
> return -EBUSY. In this case, the crypto API never calls the caller with
> -EINPROGRESS and it causes deadlock in dm-crypt.
>
> Fix this by turning -EBUSY into -EINPROGRESS.
>
> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> Cc: stable@vger.kernel.org
>
> ---
> crypto/authenc.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> Index: linux-2.6/crypto/authenc.c
> ===================================================================
> --- linux-2.6.orig/crypto/authenc.c 2025-09-22 20:32:02.000000000 +0200
> +++ linux-2.6/crypto/authenc.c 2025-09-22 20:35:38.000000000 +0200
> @@ -146,8 +146,11 @@ static int crypto_authenc_genicv(struct
> authenc_geniv_ahash_done, req);
>
> err = crypto_ahash_digest(ahreq);
> - if (err)
> + if (err) {
> + if (err == -EBUSY)
> + err = -EINPROGRESS;
> return err;
> + }

If authenc gets EBUSY from the ahash, then the ahash is responsible
for sending an EINPROGRESS notification. I just checked the authenc
code and it does pass the notification back up to the caller (which
is dm-crypt).

So if EINPROGRESS is not being received, then it's a bug in the
ahash layer or the underlying ahash algorithm.

Which phmac implementation was this?

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