crypto: cavium/nitrox - fix a DMA pool free failure

In crypto_alloc_context(), a DMA pool is allocated through dma_pool_alloc()
to hold the crypto context. The meta data of the DMA pool, including the
pool used for the allocation 'ndev->ctx_pool' and the base address of the
DMA pool used by the device 'dma', are then stored to the beginning of the
pool. These meta data are eventually used in crypto_free_context() to free
the DMA pool through dma_pool_free(). However, given that the DMA pool can
also be accessed by the device, a malicious device can modify these meta
data, especially when the device is controlled to deploy an attack. This
can cause an unexpected DMA pool free failure.

To avoid the above issue, this patch introduces a new structure
crypto_ctx_hdr and a new field chdr in the structure nitrox_crypto_ctx hold
the meta data information of the DMA pool after the allocation. Note that
the original structure ctx_hdr is not changed to ensure the compatibility.

Cc: <stable@vger.kernel.org>
Signed-off-by: Wenwen Wang <wang6495@umn.edu>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 17 insertions, 5 deletions

diff --git a/drivers/crypto/cavium/nitrox/nitrox_lib.c b/drivers/crypto/cavium/nitrox/nitrox_lib.c
index 2260efa42308..9138bae12521 100644
--- a/drivers/crypto/cavium/nitrox/nitrox_lib.c
+++ b/drivers/crypto/cavium/nitrox/nitrox_lib.c
@@ -158,12 +158,19 @@ static void destroy_crypto_dma_pool(struct nitrox_device *ndev)
 void *crypto_alloc_context(struct nitrox_device *ndev)
 {
 	struct ctx_hdr *ctx;
+	struct crypto_ctx_hdr *chdr;
 	void *vaddr;
 	dma_addr_t dma;
 
+	chdr = kmalloc(sizeof(*chdr), GFP_KERNEL);
+	if (!chdr)
+		return NULL;
+
 	vaddr = dma_pool_zalloc(ndev->ctx_pool, GFP_KERNEL, &dma);
-	if (!vaddr)
+	if (!vaddr) {
+		kfree(chdr);
 		return NULL;
+	}
 
 	/* fill meta data */
 	ctx = vaddr;
@@ -171,7 +178,11 @@ void *crypto_alloc_context(struct nitrox_device *ndev)
 	ctx->dma = dma;
 	ctx->ctx_dma = dma + sizeof(struct ctx_hdr);
 
-	return ((u8 *)vaddr + sizeof(struct ctx_hdr));
+	chdr->pool = ndev->ctx_pool;
+	chdr->dma = dma;
+	chdr->vaddr = vaddr;
+
+	return chdr;
 }
 
 /**
@@ -180,13 +191,14 @@ void *crypto_alloc_context(struct nitrox_device *ndev)
  */
 void crypto_free_context(void *ctx)
 {
-	struct ctx_hdr *ctxp;
+	struct crypto_ctx_hdr *ctxp;
 
 	if (!ctx)
 		return;
 
-	ctxp = (struct ctx_hdr *)((u8 *)ctx - sizeof(struct ctx_hdr));
-	dma_pool_free(ctxp->pool, ctxp, ctxp->dma);
+	ctxp = ctx;
+	dma_pool_free(ctxp->pool, ctxp->vaddr, ctxp->dma);
+	kfree(ctxp);
 }
 
 /**