| Message ID | 20201028090320.4222-1-horia.geanta@nxp.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | crypto: arm/aes-neonbs - fix usage of cbc(aes) fallback | expand |
On Wed, 28 Oct 2020 at 10:03, Horia Geantă <horia.geanta@nxp.com> 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 <horia.geanta@nxp.com> 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? > --- > 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 <ard.biesheuvel@linaro.org>"); > 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 >
On 10/28/2020 11:07 AM, Ard Biesheuvel wrote: > On Wed, 28 Oct 2020 at 10:03, Horia Geantă <horia.geanta@nxp.com> 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 <horia.geanta@nxp.com> > > 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. > My understanding is the following: 1. Local cbc_init() tries to allocate a fallback tfm for cbc(aes) 2. crypto API cbc(aes) tries to find a cbc(aes) algorithm implementation crypto_alloc_skcipher -> crypto_alloc_tfm -> crypto_alloc_tfm_node -> crypto_find_alg -> crypto_alg_mod_lookup -> crypto_larval_lookup Here crypto_alg_lookup() fails to find a cbc(aes) implementation. 3. Next step is to try to dynamically load a module (request_module) that supports this implementation. And here it deadlocks, since it tries to load aes-arm-bs module... The fix is providing a way to (partially) skip the dynamic module loading in crypto_alg_lookup() and allow for the last method of finding an algorithm implementation, which is creating the cbc(aes) on the fly via the cbc template - see: ok = crypto_probing_notify(CRYPTO_MSG_ALG_REQUEST, larval); in crypto_alg_mod_lookup(). Horia
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,
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 <horia.geanta@nxp.com> > --- > arch/arm/crypto/aes-neonbs-glue.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) Patch applied. Thanks.
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 <ard.biesheuvel@linaro.org>"); 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,
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 <horia.geanta@nxp.com> --- arch/arm/crypto/aes-neonbs-glue.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)