crypto: caam - fix memory corruption in ahash_final_ctx

commit b310c178 upstream.

When doing pointer operation for accessing the HW S/G table,
a value representing number of entries (and not number of bytes)
must be used.

Fixes: 045e3678 ("crypto: caam - ahash hmac support")
Signed-off-by: Horia Geant? <horia.geanta@freescale.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/crypto/caam/caamhash.c

@@ -890,13 +890,14 @@ static int ahash_final_ctx(struct ahash_request *req)
 			  state->buflen_1;
 	u32 *sh_desc = ctx->sh_desc_fin, *desc;
 	dma_addr_t ptr = ctx->sh_desc_fin_dma;
-	int sec4_sg_bytes;
+	int sec4_sg_bytes, sec4_sg_src_index;
 	int digestsize = crypto_ahash_digestsize(ahash);
 	struct ahash_edesc *edesc;
 	int ret = 0;
 	int sh_len;
 
-	sec4_sg_bytes = (1 + (buflen ? 1 : 0)) * sizeof(struct sec4_sg_entry);
+	sec4_sg_src_index = 1 + (buflen ? 1 : 0);
+	sec4_sg_bytes = sec4_sg_src_index * sizeof(struct sec4_sg_entry);
 
 	/* allocate space for base edesc and hw desc commands, link tables */
 	edesc = kmalloc(sizeof(struct ahash_edesc) + DESC_JOB_IO_LEN +
@@ -923,7 +924,7 @@ static int ahash_final_ctx(struct ahash_request *req)
 	state->buf_dma = try_buf_map_to_sec4_sg(jrdev, edesc->sec4_sg + 1,
 						buf, state->buf_dma, buflen,
 						last_buflen);
-	(edesc->sec4_sg + sec4_sg_bytes - 1)->len |= SEC4_SG_LEN_FIN;
+	(edesc->sec4_sg + sec4_sg_src_index - 1)->len |= SEC4_SG_LEN_FIN;
 
 	append_seq_in_ptr(desc, edesc->sec4_sg_dma, ctx->ctx_len + buflen,
 			  LDST_SGF);