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Date:   Tue, 26 May 2020 11:19:55 +0800
From:   "Longpeng(Mike)" <longpeng2@...wei.com>
To:     <linux-crypto@...r.kernel.org>
CC:     "Longpeng(Mike)" <longpeng2@...wei.com>,
        LABBE Corentin <clabbe@...libre.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>,
        Markus Elfring <Markus.Elfring@....de>,
        <virtualization@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>,
        Gonglei <arei.gonglei@...wei.com>
Subject: [PATCH v2 1/2] crypto: virtio: Fix src/dst scatterlist calculation in __virtio_crypto_skcipher_do_req()

The system will crash when the users insmod crypto/tcrypt.ko with mode=38
( testing "cts(cbc(aes))" ).

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. Fix it by sg_next() on calculation of src/dst
scatterlist.

Fixes: dbaf0624ffa5 ("crypto: add virtio-crypto driver")
Reported-by: LABBE Corentin <clabbe@...libre.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: Markus Elfring <Markus.Elfring@....de>
Cc: virtualization@...ts.linux-foundation.org
Cc: linux-kernel@...r.kernel.org
Cc: stable@...r.kernel.org
Message-Id: <20200123101000.GB24255@Red>
Signed-off-by: Gonglei <arei.gonglei@...wei.com>
Signed-off-by: Longpeng(Mike) <longpeng2@...wei.com>
---
 drivers/crypto/virtio/virtio_crypto_algs.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/crypto/virtio/virtio_crypto_algs.c b/drivers/crypto/virtio/virtio_crypto_algs.c
index fd045e64972a..5f8243563009 100644
--- a/drivers/crypto/virtio/virtio_crypto_algs.c
+++ b/drivers/crypto/virtio/virtio_crypto_algs.c
@@ -350,13 +350,18 @@ __virtio_crypto_skcipher_do_req(struct virtio_crypto_sym_request *vc_sym_req,
 	int err;
 	unsigned long flags;
 	struct scatterlist outhdr, iv_sg, status_sg, **sgs;
-	int i;
 	u64 dst_len;
 	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",
@@ -442,12 +447,12 @@ __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; src_nents; sg = sg_next(sg), src_nents--)
+		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; sg; sg = sg_next(sg))
+		sgs[num_out + num_in++] = sg;
 
 	/* Status */
 	sg_init_one(&status_sg, &vc_req->status, sizeof(vc_req->status));
-- 
2.23.0

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