crypto: nx - Fixing the limit number of bytes to be processed

The previous limits were estimated locally in a single step
basead on bound values, however it was not correct since
when given certain scatterlist the function nx_build_sg_lists
was consuming more sg entries than allocated causing a
memory corruption and crashes.

e.g.: in the worst case we could have one sg entry for a single byte.

This patch fixes it modifying the logic of the bound limit
moving it to nx_sg_build_lists and set a correct sg_max limit,
adding a trim function to ensure the bound in sg_list. Also fixing
nx_build_sg_list  NULL and untreated return in case of overflow.

Signed-off-by: Leonidas S. Barbosa <leosilva@linux.vnet.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/nx/nx.h

@@ -153,13 +153,15 @@ void nx_crypto_ctx_exit(struct crypto_tfm *tfm);
 void nx_ctx_init(struct nx_crypto_ctx *nx_ctx, unsigned int function);
 int nx_hcall_sync(struct nx_crypto_ctx *ctx, struct vio_pfo_op *op,
 		  u32 may_sleep);
-struct nx_sg *nx_build_sg_list(struct nx_sg *, u8 *, unsigned int, u32);
+int nx_sha_build_sg_list(struct nx_crypto_ctx *, struct nx_sg *,
+			 s64 *, unsigned int *, u8 *, u32);
+struct nx_sg *nx_build_sg_list(struct nx_sg *, u8 *, unsigned int *, u32);
 int nx_build_sg_lists(struct nx_crypto_ctx *, struct blkcipher_desc *,
-		      struct scatterlist *, struct scatterlist *, unsigned int,
+		      struct scatterlist *, struct scatterlist *, unsigned int *,
 		      unsigned int, u8 *);
 struct nx_sg *nx_walk_and_build(struct nx_sg *, unsigned int,
 				struct scatterlist *, unsigned int,
-				unsigned int);
+				unsigned int *);
 
 #ifdef CONFIG_DEBUG_FS
 #define NX_DEBUGFS_INIT(drv)	nx_debugfs_init(drv)