crypto: Replace zero-length array with flexible-array member

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Horia Geantă <horia.geanta@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

4 files changed, 7 insertions, 7 deletions

diff --git a/drivers/crypto/caam/caamalg.c b/drivers/crypto/caam/caamalg.c
index 03797f9b1050..b7bb7c30adeb 100644
--- a/drivers/crypto/caam/caamalg.c
+++ b/drivers/crypto/caam/caamalg.c
@@ -909,7 +909,7 @@ struct skcipher_edesc {
 	bool bklog;
 	dma_addr_t sec4_sg_dma;
 	struct sec4_sg_entry *sec4_sg;
-	u32 hw_desc[0];
+	u32 hw_desc[];
 };
 
 static void caam_unmap(struct device *dev, struct scatterlist *src,
diff --git a/drivers/crypto/caam/caamalg_qi.c b/drivers/crypto/caam/caamalg_qi.c
index 4a29e0ef9d63..27e36bdf6163 100644
--- a/drivers/crypto/caam/caamalg_qi.c
+++ b/drivers/crypto/caam/caamalg_qi.c
@@ -783,7 +783,7 @@ struct aead_edesc {
 	unsigned int assoclen;
 	dma_addr_t assoclen_dma;
 	struct caam_drv_req drv_req;
-	struct qm_sg_entry sgt[0];
+	struct qm_sg_entry sgt[];
 };
 
 /*
@@ -803,7 +803,7 @@ struct skcipher_edesc {
 	int qm_sg_bytes;
 	dma_addr_t qm_sg_dma;
 	struct caam_drv_req drv_req;
-	struct qm_sg_entry sgt[0];
+	struct qm_sg_entry sgt[];
 };
 
 static struct caam_drv_ctx *get_drv_ctx(struct caam_ctx *ctx,
diff --git a/drivers/crypto/caam/caamalg_qi2.h b/drivers/crypto/caam/caamalg_qi2.h
index 706736776b47..f29cb7bd7dd3 100644
--- a/drivers/crypto/caam/caamalg_qi2.h
+++ b/drivers/crypto/caam/caamalg_qi2.h
@@ -114,7 +114,7 @@ struct aead_edesc {
 	dma_addr_t qm_sg_dma;
 	unsigned int assoclen;
 	dma_addr_t assoclen_dma;
-	struct dpaa2_sg_entry sgt[0];
+	struct dpaa2_sg_entry sgt[];
 };
 
 /*
@@ -132,7 +132,7 @@ struct skcipher_edesc {
 	dma_addr_t iv_dma;
 	int qm_sg_bytes;
 	dma_addr_t qm_sg_dma;
-	struct dpaa2_sg_entry sgt[0];
+	struct dpaa2_sg_entry sgt[];
 };
 
 /*
@@ -146,7 +146,7 @@ struct ahash_edesc {
 	dma_addr_t qm_sg_dma;
 	int src_nents;
 	int qm_sg_bytes;
-	struct dpaa2_sg_entry sgt[0];
+	struct dpaa2_sg_entry sgt[];
 };
 
 /**
diff --git a/drivers/crypto/caam/caamhash.c b/drivers/crypto/caam/caamhash.c
index 2fe852853d40..943bc0296267 100644
--- a/drivers/crypto/caam/caamhash.c
+++ b/drivers/crypto/caam/caamhash.c
@@ -536,7 +536,7 @@ struct ahash_edesc {
 	int sec4_sg_bytes;
 	bool bklog;
 	u32 hw_desc[DESC_JOB_IO_LEN_MAX / sizeof(u32)] ____cacheline_aligned;
-	struct sec4_sg_entry sec4_sg[0];
+	struct sec4_sg_entry sec4_sg[];
 };
 
 static inline void ahash_unmap(struct device *dev,