2020-10-28 22:00:37

by Horia Geanta

Subject: [PATCH] crypto: arm/aes-neonbs - fix usage of cbc(aes) fallback

Loading the module deadlocks since:
-local cbc(aes) implementation needs a fallback and
-crypto API tries to find one but the request_module() resolves back to
the same module

Fix this by changing the module alias for cbc(aes) and
using the NEED_FALLBACK flag when requesting for a fallback algorithm.

Fixes: 00b99ad2bac2 ("crypto: arm/aes-neonbs - Use generic cbc encryption path")
Signed-off-by: Horia Geantă <[email protected]>
---
arch/arm/crypto/aes-neonbs-glue.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/arm/crypto/aes-neonbs-glue.c b/arch/arm/crypto/aes-neonbs-glue.c
index bda8bf17631e..f70af1d0514b 100644
--- a/arch/arm/crypto/aes-neonbs-glue.c
+++ b/arch/arm/crypto/aes-neonbs-glue.c
@@ -19,7 +19,7 @@ MODULE_AUTHOR("Ard Biesheuvel <[email protected]>");
MODULE_LICENSE("GPL v2");

MODULE_ALIAS_CRYPTO("ecb(aes)");
-MODULE_ALIAS_CRYPTO("cbc(aes)");
+MODULE_ALIAS_CRYPTO("cbc(aes)-all");
MODULE_ALIAS_CRYPTO("ctr(aes)");
MODULE_ALIAS_CRYPTO("xts(aes)");

@@ -191,7 +191,8 @@ static int cbc_init(struct crypto_skcipher *tfm)
struct aesbs_cbc_ctx *ctx = crypto_skcipher_ctx(tfm);
unsigned int reqsize;

- ctx->enc_tfm = crypto_alloc_skcipher("cbc(aes)", 0, CRYPTO_ALG_ASYNC);
+ ctx->enc_tfm = crypto_alloc_skcipher("cbc(aes)", 0, CRYPTO_ALG_ASYNC |
+ CRYPTO_ALG_NEED_FALLBACK);
if (IS_ERR(ctx->enc_tfm))
return PTR_ERR(ctx->enc_tfm);

@@ -441,7 +442,8 @@ static struct skcipher_alg aes_algs[] = { {
.base.cra_blocksize = AES_BLOCK_SIZE,
.base.cra_ctxsize = sizeof(struct aesbs_cbc_ctx),
.base.cra_module = THIS_MODULE,
- .base.cra_flags = CRYPTO_ALG_INTERNAL,
+ .base.cra_flags = CRYPTO_ALG_INTERNAL |
+ CRYPTO_ALG_NEED_FALLBACK,

.min_keysize = AES_MIN_KEY_SIZE,
.max_keysize = AES_MAX_KEY_SIZE,
--
2.17.1

2020-10-29 09:15:50

by Herbert Xu

Subject: Re: [PATCH] crypto: arm/aes-neonbs - fix usage of cbc(aes) fallback

On Wed, Oct 28, 2020 at 10:06:58AM +0100, Ard Biesheuvel wrote:
>
> Not sure what is happening here: IIRC the intention was to rely on the
> fact that only the sync cbc(aes) implementation needs the fallback,
> and therefore, allocating a sync skcipher explicitly would avoid this
> recursion.
>
> Herbert?

It works only if everything is built in. If cbc is built as a
module then you need Horia's patch to prevent a loop.

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

2020-11-06 07:03:28

by Herbert Xu

Subject: Re: [PATCH] crypto: arm/aes-neonbs - fix usage of cbc(aes) fallback

On Wed, Oct 28, 2020 at 11:03:20AM +0200, Horia Geantă wrote:
> Loading the module deadlocks since:
> -local cbc(aes) implementation needs a fallback and
> -crypto API tries to find one but the request_module() resolves back to
> the same module
>
> Fix this by changing the module alias for cbc(aes) and
> using the NEED_FALLBACK flag when requesting for a fallback algorithm.
>
> Fixes: 00b99ad2bac2 ("crypto: arm/aes-neonbs - Use generic cbc encryption path")
> Signed-off-by: Horia Geantă <[email protected]>
> ---
> arch/arm/crypto/aes-neonbs-glue.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)

Patch applied. Thanks.
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt