From 877b5691f27a1aec0d9b53095a323e45c30069e2 Mon Sep 17 00:00:00 2001

From: Eric Biggers <ebiggers@google.com>

Date: Sun, 14 Apr 2019 17:37:09 -0700

Subject: [Backport 877b5691f27a] 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>

---

 src/crypto.c   | 1 -

 src/keystore.c | 1 -

 2 files changed, 2 deletions(-)

diff --git a/src/crypto.c b/src/crypto.c

index f664da55234e93b18194237e9995a16c70f1334d..491cf5baa8c23b5f97254f4d5cb43d32e3339f8f 100644

--- a/src/crypto.c

+++ b/src/crypto.c

@@ -68,7 +68,6 @@ static int ecryptfs_hash_digest(struct crypto_shash *tfm,

 	int err;

 	desc->tfm = tfm;

-	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;

 	err = crypto_shash_digest(desc, src, len, dst);

 	shash_desc_zero(desc);

 	return err;

diff --git a/src/keystore.c b/src/keystore.c

index e74fe84d0886879c04cc26297f0e8b27db8281a6..90fbac5d485b3a79728f342e81e2bcdaa8b0e552 100644

--- a/src/keystore.c

+++ b/src/keystore.c

@@ -769,7 +769,6 @@ ecryptfs_write_tag_70_packet(char *dest, size_t *remaining_bytes,

 	}

 	s->hash_desc->tfm = s->hash_tfm;

-	s->hash_desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;

 	rc = crypto_shash_digest(s->hash_desc,

 				 (u8 *)s->auth_tok->token.password.session_key_encryption_key,

-- 

2.31.1