libceph: introduce ceph_crypt() for in-place en/decryption

Starting with 4.9, kernel stacks may be vmalloced and therefore not
guaranteed to be physically contiguous; the new CONFIG_VMAP_STACK
option is enabled by default on x86.  This makes it invalid to use
on-stack buffers with the crypto scatterlist API, as sg_set_buf()
expects a logical address and won't work with vmalloced addresses.

There isn't a different (e.g. kvec-based) crypto API we could switch
net/ceph/crypto.c to and the current scatterlist.h API isn't getting
updated to accommodate this use case.  Allocating a new header and
padding for each operation is a non-starter, so do the en/decryption
in-place on a single pre-assembled (header + data + padding) heap
buffer.  This is explicitly supported by the crypto API:

    "... the caller may provide the same scatter/gather list for the
     plaintext and cipher text. After the completion of the cipher
     operation, the plaintext data is replaced with the ciphertext data
     in case of an encryption and vice versa for a decryption."

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/ceph/crypto.h b/net/ceph/crypto.h
index 2e9cab09f37b..73da34e8c62e 100644
--- a/net/ceph/crypto.h
+++ b/net/ceph/crypto.h
@@ -43,6 +43,8 @@ int ceph_encrypt2(struct ceph_crypto_key *secret,
 		  void *dst, size_t *dst_len,
 		  const void *src1, size_t src1_len,
 		  const void *src2, size_t src2_len);
+int ceph_crypt(const struct ceph_crypto_key *key, bool encrypt,
+	       void *buf, int buf_len, int in_len, int *pout_len);
 int ceph_crypto_init(void);
 void ceph_crypto_shutdown(void);