crypto: caam - use len instead of nents for bulding HW S/G table

Currently, conversion of SW S/G table into HW S/G layout relies on
nents returned by sg_nents_for_len(sg, len).
However this leaves the possibility of HW S/G referencing more data
then needed: since buffer length in HW S/G entries is filled using
sg_dma_len(sg), the last entry in HW S/G table might have a length
that is bigger than needed for the crypto request.

This way of S/G table conversion is fine, unless after converting a table
more entries have to be appended to the HW S/G table.
In this case, crypto engine would access data from the S/G entry having
the incorrect length, instead of advancing in the S/G table.
This situation doesn't exist, but the upcoming implementation of
IV update for skcipher algorithms needs to add a S/G entry after
req->dst S/G (corresponding to output IV).

Signed-off-by: Horia Geantă <horia.geanta@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 11 insertions, 7 deletions

diff --git a/drivers/crypto/caam/sg_sw_qm.h b/drivers/crypto/caam/sg_sw_qm.h
index b3e1aaaeffea..d56cc7efbc13 100644
--- a/drivers/crypto/caam/sg_sw_qm.h
+++ b/drivers/crypto/caam/sg_sw_qm.h
@@ -54,15 +54,19 @@ static inline void dma_to_qm_sg_one_last_ext(struct qm_sg_entry *qm_sg_ptr,
  * but does not have final bit; instead, returns last entry
  */
 static inline struct qm_sg_entry *
-sg_to_qm_sg(struct scatterlist *sg, int sg_count,
+sg_to_qm_sg(struct scatterlist *sg, int len,
 	    struct qm_sg_entry *qm_sg_ptr, u16 offset)
 {
-	while (sg_count && sg) {
-		dma_to_qm_sg_one(qm_sg_ptr, sg_dma_address(sg),
-				 sg_dma_len(sg), offset);
+	int ent_len;
+
+	while (len) {
+		ent_len = min_t(int, sg_dma_len(sg), len);
+
+		dma_to_qm_sg_one(qm_sg_ptr, sg_dma_address(sg), ent_len,
+				 offset);
 		qm_sg_ptr++;
 		sg = sg_next(sg);
-		sg_count--;
+		len -= ent_len;
 	}
 	return qm_sg_ptr - 1;
 }
@@ -71,10 +75,10 @@ sg_to_qm_sg(struct scatterlist *sg, int sg_count,
  * convert scatterlist to h/w link table format
  * scatterlist must have been previously dma mapped
  */
-static inline void sg_to_qm_sg_last(struct scatterlist *sg, int sg_count,
+static inline void sg_to_qm_sg_last(struct scatterlist *sg, int len,
 				    struct qm_sg_entry *qm_sg_ptr, u16 offset)
 {
-	qm_sg_ptr = sg_to_qm_sg(sg, sg_count, qm_sg_ptr, offset);
+	qm_sg_ptr = sg_to_qm_sg(sg, len, qm_sg_ptr, offset);
 	qm_sg_entry_set_f(qm_sg_ptr, qm_sg_entry_get_len(qm_sg_ptr));
 }