crypto: qat - validate RSA CRT component lengths

commit b3ac787 upstream.

The generic RSA key parser (rsa_helper.c) bounds each CRT component (p,
q, dp, dq, qinv) by the modulus size n_sz, but qat_rsa_setkey_crt()
allocates half-size DMA buffers (key_sz / 2) and right-aligns each
component with:

    memcpy(dst + half_key_sz - len, src, len)

When a CRT component is larger than half_key_sz the subtraction
underflows and memcpy writes past the DMA buffer, causing memory
corruption.

Add a len > half_key_sz check next to the existing !len check for each
of the five CRT components so the driver falls back to the non-CRT path
instead of writing out of bounds.

Fixes: 879f77e ("crypto: qat - Add RSA CRT mode")
Cc: stable@vger.kernel.org
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Ahsan Atta <ahsan.atta@intel.com>
Reviewed-by: Laurent M Coquerel <laurent.m.coquerel@intel.com>
Tested-by: Laurent M Coquerel <laurent.m.coquerel@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: gcabiddu

drivers/crypto/intel/qat/qat_common/qat_asym_algs.c

@@ -1032,7 +1032,7 @@ static void qat_rsa_setkey_crt(struct qat_rsa_ctx *ctx, struct rsa_key *rsa_key)
 	ptr = rsa_key->p;
 	len = rsa_key->p_sz;
 	qat_rsa_drop_leading_zeros(&ptr, &len);
-	if (!len)
+	if (!len || len > half_key_sz)
 		goto err;
 	ctx->p = dma_alloc_coherent(dev, half_key_sz, &ctx->dma_p, GFP_KERNEL);
 	if (!ctx->p)
@@ -1043,7 +1043,7 @@ static void qat_rsa_setkey_crt(struct qat_rsa_ctx *ctx, struct rsa_key *rsa_key)
 	ptr = rsa_key->q;
 	len = rsa_key->q_sz;
 	qat_rsa_drop_leading_zeros(&ptr, &len);
-	if (!len)
+	if (!len || len > half_key_sz)
 		goto free_p;
 	ctx->q = dma_alloc_coherent(dev, half_key_sz, &ctx->dma_q, GFP_KERNEL);
 	if (!ctx->q)
@@ -1054,7 +1054,7 @@ static void qat_rsa_setkey_crt(struct qat_rsa_ctx *ctx, struct rsa_key *rsa_key)
 	ptr = rsa_key->dp;
 	len = rsa_key->dp_sz;
 	qat_rsa_drop_leading_zeros(&ptr, &len);
-	if (!len)
+	if (!len || len > half_key_sz)
 		goto free_q;
 	ctx->dp = dma_alloc_coherent(dev, half_key_sz, &ctx->dma_dp,
 				     GFP_KERNEL);
@@ -1066,7 +1066,7 @@ static void qat_rsa_setkey_crt(struct qat_rsa_ctx *ctx, struct rsa_key *rsa_key)
 	ptr = rsa_key->dq;
 	len = rsa_key->dq_sz;
 	qat_rsa_drop_leading_zeros(&ptr, &len);
-	if (!len)
+	if (!len || len > half_key_sz)
 		goto free_dp;
 	ctx->dq = dma_alloc_coherent(dev, half_key_sz, &ctx->dma_dq,
 				     GFP_KERNEL);
@@ -1078,7 +1078,7 @@ static void qat_rsa_setkey_crt(struct qat_rsa_ctx *ctx, struct rsa_key *rsa_key)
 	ptr = rsa_key->qinv;
 	len = rsa_key->qinv_sz;
 	qat_rsa_drop_leading_zeros(&ptr, &len);
-	if (!len)
+	if (!len || len > half_key_sz)
 		goto free_dq;
 	ctx->qinv = dma_alloc_coherent(dev, half_key_sz, &ctx->dma_qinv,
 				       GFP_KERNEL);