crypto: shash - remove shash_desc::flags

The flags field in 'struct shash_desc' never actually does anything.
The only ostensibly supported flag is CRYPTO_TFM_REQ_MAY_SLEEP.
However, no shash algorithm ever sleeps, making this flag a no-op.

With this being the case, inevitably some users who can't sleep wrongly
pass MAY_SLEEP.  These would all need to be fixed if any shash algorithm
actually started sleeping.  For example, the shash_ahash_*() functions,
which wrap a shash algorithm with the ahash API, pass through MAY_SLEEP
from the ahash API to the shash API.  However, the shash functions are
called under kmap_atomic(), so actually they're assumed to never sleep.

Even if it turns out that some users do need preemption points while
hashing large buffers, we could easily provide a helper function
crypto_shash_update_large() which divides the data into smaller chunks
and calls crypto_shash_update() and cond_resched() for each chunk.  It's
not necessary to have a flag in 'struct shash_desc', nor is it necessary
to make individual shash algorithms aware of this at all.

Therefore, remove shash_desc::flags, and document that the
crypto_shash_*() functions can be called from any context.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

net/bluetooth/amp.c

@@ -161,7 +161,6 @@ static int hmac_sha256(u8 *key, u8 ksize, char *plaintext, u8 psize, u8 *output)
 	}
 
 	shash->tfm = tfm;
-	shash->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
 
 	ret = crypto_shash_digest(shash, plaintext, psize, output);
 

net/bluetooth/smp.c

@@ -183,7 +183,6 @@ static int aes_cmac(struct crypto_shash *tfm, const u8 k[16], const u8 *m,
 	}
 
 	desc->tfm = tfm;
-	desc->flags = 0;
 
 	/* Swap key and message from LSB to MSB */
 	swap_buf(k, tmp, 16);

net/sctp/auth.c

@@ -760,7 +760,6 @@ void sctp_auth_calculate_hmac(const struct sctp_association *asoc,
 		SHASH_DESC_ON_STACK(desc, tfm);
 
 		desc->tfm = tfm;
-		desc->flags = 0;
 		crypto_shash_digest(desc, (u8 *)auth,
 				    end - (unsigned char *)auth, digest);
 		shash_desc_zero(desc);

net/sctp/sm_make_chunk.c

@@ -1684,7 +1684,6 @@ static struct sctp_cookie_param *sctp_pack_cookie(
 
 		/* Sign the message.  */
 		desc->tfm = sctp_sk(ep->base.sk)->hmac;
-		desc->flags = 0;
 
 		err = crypto_shash_setkey(desc->tfm, ep->secret_key,
 					  sizeof(ep->secret_key)) ?:
@@ -1755,7 +1754,6 @@ struct sctp_association *sctp_unpack_cookie(
 		int err;
 
 		desc->tfm = sctp_sk(ep->base.sk)->hmac;
-		desc->flags = 0;
 
 		err = crypto_shash_setkey(desc->tfm, ep->secret_key,
 					  sizeof(ep->secret_key)) ?:

net/sunrpc/auth_gss/gss_krb5_crypto.c

@@ -977,7 +977,6 @@ krb5_rc4_setup_seq_key(struct krb5_ctx *kctx,
 	}
 
 	desc->tfm = hmac;
-	desc->flags = 0;
 
 	/* Compute intermediate Kseq from session key */
 	err = crypto_shash_setkey(hmac, kctx->Ksess, kctx->gk5e->keylength);
@@ -1045,7 +1044,6 @@ krb5_rc4_setup_enc_key(struct krb5_ctx *kctx,
 	}
 
 	desc->tfm = hmac;
-	desc->flags = 0;
 
 	/* Compute intermediate Kcrypt from session key */
 	for (i = 0; i < kctx->gk5e->keylength; i++)

net/sunrpc/auth_gss/gss_krb5_mech.c

@@ -438,7 +438,6 @@ context_derive_keys_rc4(struct krb5_ctx *ctx)
 	}
 
 	desc->tfm = hmac;
-	desc->flags = 0;
 
 	err = crypto_shash_digest(desc, sigkeyconstant, slen, ctx->cksum);
 	kzfree(desc);

net/wireless/lib80211_crypt_tkip.c

@@ -501,7 +501,6 @@ static int michael_mic(struct crypto_shash *tfm_michael, u8 *key, u8 *hdr,
 	}
 
 	desc->tfm = tfm_michael;
-	desc->flags = 0;
 
 	if (crypto_shash_setkey(tfm_michael, key, 8))
 		return -1;