[PATCH AUTOSEL for 4.9 239/281] crypto: omap-sham - buffer handling fixes for hashing later

[Sasha Levin]

From: Tero Kristo <t-kristo@xxxxxx>

[ Upstream commit 5d78d57ede8f9e7f656c610ed25be7be337e0529 ]

Currently, the hash later code only handles the cases when we have
either new data coming in with the request or old data in the buffer,
but not the combination when we have both. Fix this by changing the
ordering of the code a bit and handling both cases properly
simultaneously if needed. Also, fix an issue with omap_sham_update
that surfaces with this fix, so that the code checks the bufcnt
instead of total data amount against buffer length to avoid any
buffer overflows.

Signed-off-by: Tero Kristo <t-kristo@xxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
 drivers/crypto/omap-sham.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/crypto/omap-sham.c b/drivers/crypto/omap-sham.c
index d0b16e5e4ee5..c65b49baf0c7 100644
--- a/drivers/crypto/omap-sham.c
+++ b/drivers/crypto/omap-sham.c
@@ -873,14 +873,21 @@ static int omap_sham_prepare_request(struct ahash_request *req, bool update)
 	}
 
 	if (hash_later) {
-		if (req->nbytes) {
-			scatterwalk_map_and_copy(rctx->buffer, req->src,
-						 req->nbytes - hash_later,
-						 hash_later, 0);
-		} else {
+		int offset = 0;
+
+		if (hash_later > req->nbytes) {
 			memcpy(rctx->buffer, rctx->buffer + xmit_len,
-			       hash_later);
+			       hash_later - req->nbytes);
+			offset = hash_later - req->nbytes;
 		}
+
+		if (req->nbytes) {
+			scatterwalk_map_and_copy(rctx->buffer + offset,
+						 req->src,
+						 offset + req->nbytes -
+						 hash_later, hash_later, 0);
+		}
+
 		rctx->bufcnt = hash_later;
 	} else {
 		rctx->bufcnt = 0;
@@ -1189,11 +1196,10 @@ static int omap_sham_update(struct ahash_request *req)
 	if (!req->nbytes)
 		return 0;
 
-	if (ctx->total + req->nbytes < ctx->buflen) {
+	if (ctx->bufcnt + req->nbytes <= ctx->buflen) {
 		scatterwalk_map_and_copy(ctx->buffer + ctx->bufcnt, req->src,
 					 0, req->nbytes, 0);
 		ctx->bufcnt += req->nbytes;
-		ctx->total += req->nbytes;
 		return 0;
 	}
 
-- 
2.14.1