[HIFN]: Properly handle requests for less than the full scatterlist

    
The scatterlist may contain more data than the crypto request, causing
an underflow of the remaining byte count while walking the list.
    
Use the minimum of the scatterlist element size and the remaining byte
count specified in the crypto request to avoid this.
    
Signed-off-by: Patrick McHardy <kaber@trash.net>
Acked-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/hifn_795x.c

@@ -1433,7 +1433,7 @@ static int ablkcipher_add(void *daddr, unsigned int *drestp, struct scatterlist
 		return -EINVAL;
 
 	while (size) {
-		copy = min(drest, src->length);
+		copy = min(drest, min(size, src->length));
 
 		saddr = kmap_atomic(sg_page(src), KM_SOFTIRQ1);
 		memcpy(daddr, saddr + src->offset, copy);
@@ -1482,7 +1482,7 @@ static int ablkcipher_walk(struct ablkcipher_request *req,
 		if (!IS_ALIGNED(dst->offset, HIFN_D_DST_DALIGN) ||
 		    !IS_ALIGNED(dst->length, HIFN_D_DST_DALIGN) ||
 		    offset) {
-			unsigned slen = src->length - offset;
+			unsigned slen = min(src->length - offset, nbytes);
 			unsigned dlen = PAGE_SIZE;
 
 			t = &w->cache[idx];
@@ -1540,7 +1540,7 @@ static int ablkcipher_walk(struct ablkcipher_request *req,
 
 			kunmap_atomic(daddr, KM_SOFTIRQ0);
 		} else {
-			nbytes -= src->length;
+			nbytes -= min(src->length, nbytes);
 			idx++;
 		}
 
@@ -1559,7 +1559,7 @@ static int hifn_setup_session(struct ablkcipher_request *req)
 	struct hifn_context *ctx = crypto_tfm_ctx(req->base.tfm);
 	struct hifn_device *dev = ctx->dev;
 	struct page *spage, *dpage;
-	unsigned long soff, doff, flags;
+	unsigned long soff, doff, dlen, flags;
 	unsigned int nbytes = req->nbytes, idx = 0, len;
 	int err = -EINVAL, sg_num;
 	struct scatterlist *src, *dst, *t;
@@ -1571,12 +1571,13 @@ static int hifn_setup_session(struct ablkcipher_request *req)
 
 	while (nbytes) {
 		dst = &req->dst[idx];
+		dlen = min(dst->length, nbytes);
 
 		if (!IS_ALIGNED(dst->offset, HIFN_D_DST_DALIGN) ||
-		    !IS_ALIGNED(dst->length, HIFN_D_DST_DALIGN))
+		    !IS_ALIGNED(dlen, HIFN_D_DST_DALIGN))
 			ctx->walk.flags |= ASYNC_FLAGS_MISALIGNED;
 
-		nbytes -= dst->length;
+		nbytes -= dlen;
 		idx++;
 	}
 
@@ -1631,7 +1632,7 @@ static int hifn_setup_session(struct ablkcipher_request *req)
 		if (err)
 			goto err_out;
 
-		nbytes -= len;
+		nbytes -= min(len, nbytes);
 	}
 
 	dev->active = HIFN_DEFAULT_ACTIVE_NUM;
@@ -1736,8 +1737,7 @@ static int ablkcipher_get(void *saddr, unsigned int *srestp, unsigned int offset
 		return -EINVAL;
 
 	while (size) {
-
-		copy = min(dst->length, srest);
+		copy = min(srest, min(dst->length, size));
 
 		daddr = kmap_atomic(sg_page(dst), KM_IRQ0);
 		memcpy(daddr + dst->offset + offset, saddr, copy);
@@ -1794,7 +1794,7 @@ static void hifn_process_ready(struct ablkcipher_request *req, int error)
 					sg_page(dst), dst->length, nbytes);
 
 				if (!t->length) {
-					nbytes -= dst->length;
+					nbytes -= min(dst->length, nbytes);
 					idx++;
 					continue;
 				}