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