linux-kernel - [PATCH 1/2] crypto: virtio: fix src/dst scatterlist calculation

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Date:   Mon, 25 May 2020 08:56:26 +0800
From:   "Longpeng(Mike)" <longpeng2@...wei.com>
To:     <linux-crypto@...r.kernel.org>
CC:     "Longpeng(Mike)" <longpeng2@...wei.com>,
        Gonglei <arei.gonglei@...wei.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        <virtualization@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>,
        LABBE Corentin <clabbe@...libre.com>
Subject: [PATCH 1/2] crypto: virtio: fix src/dst scatterlist calculation

The system will crash when we insmod crypto/tcrypt.ko whit mode=38.

Usually the next entry of one sg will be @sg@ + 1, but if this sg element
is part of a chained scatterlist, it could jump to the start of a new
scatterlist array. Let's fix it by sg_next() on calculation of src/dst
scatterlist.

BTW I add a check for sg_nents_for_len() its return value since
sg_nents_for_len() function could fail.

Cc: Gonglei <arei.gonglei@...wei.com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>
Cc: "Michael S. Tsirkin" <mst@...hat.com>
Cc: Jason Wang <jasowang@...hat.com>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: virtualization@...ts.linux-foundation.org
Cc: linux-kernel@...r.kernel.org

Reported-by: LABBE Corentin <clabbe@...libre.com>
Signed-off-by: Gonglei <arei.gonglei@...wei.com>
Signed-off-by: Longpeng(Mike) <longpeng2@...wei.com>
---
 drivers/crypto/virtio/virtio_crypto_algs.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/crypto/virtio/virtio_crypto_algs.c b/drivers/crypto/virtio/virtio_crypto_algs.c
index 372babb44112..2fa1129f96d6 100644
--- a/drivers/crypto/virtio/virtio_crypto_algs.c
+++ b/drivers/crypto/virtio/virtio_crypto_algs.c
@@ -359,8 +359,14 @@ __virtio_crypto_skcipher_do_req(struct virtio_crypto_sym_request *vc_sym_req,
 	unsigned int num_out = 0, num_in = 0;
 	int sg_total;
 	uint8_t *iv;
+	struct scatterlist *sg;
 
 	src_nents = sg_nents_for_len(req->src, req->cryptlen);
+	if (src_nents < 0) {
+		pr_err("Invalid number of src SG.\n");
+		return src_nents;
+	}
+
 	dst_nents = sg_nents(req->dst);
 
 	pr_debug("virtio_crypto: Number of sgs (src_nents: %d, dst_nents: %d)\n",
@@ -446,12 +452,12 @@ __virtio_crypto_skcipher_do_req(struct virtio_crypto_sym_request *vc_sym_req,
 	vc_sym_req->iv = iv;
 
 	/* Source data */
-	for (i = 0; i < src_nents; i++)
-		sgs[num_out++] = &req->src[i];
+	for (sg = req->src, i = 0; sg && i < src_nents; sg = sg_next(sg), i++)
+		sgs[num_out++] = sg;
 
 	/* Destination data */
-	for (i = 0; i < dst_nents; i++)
-		sgs[num_out + num_in++] = &req->dst[i];
+	for (sg = req->dst, i = 0; sg && i < dst_nents; sg = sg_next(sg), i++)
+		sgs[num_out + num_in++] = sg;
 
 	/* Status */
 	sg_init_one(&status_sg, &vc_req->status, sizeof(vc_req->status));
-- 
2.17.1