[PATCH 07/32] iwlwifi: calib: Use mem_to_flex_dup() with struct iwl_calib_result

[Kees Cook]

As part of the work to perform bounds checking on all memcpy() uses,
replace the open-coded a deserialization of bytes out of memory into a
trailing flexible array by using a flex_array.h helper to perform the
allocation, bounds checking, and copying.

Avoids future false-positive warning when strict run-time memcpy()
bounds checking is enabled:

memcpy: detected field-spanning write (size 8) of single field "&res->hdr" (size 4)

Adds an additional size check since the minimum isn't 0.

Reported-by: Andy Lavr <andy.lavr at gmail.com>
Cc: Luca Coelho <luciano.coelho at intel.com>
Cc: Kalle Valo <kvalo at kernel.org>
Cc: "David S. Miller" <davem at davemloft.net>
Cc: Jakub Kicinski <kuba at kernel.org>
Cc: Paolo Abeni <pabeni at redhat.com>
Cc: Gregory Greenman <gregory.greenman at intel.com>
Cc: Eric Dumazet <edumazet at google.com>
Cc: linux-wireless at vger.kernel.org
Cc: netdev at vger.kernel.org
Signed-off-by: Kees Cook <keescook at chromium.org>
---
 drivers/net/wireless/intel/iwlwifi/dvm/calib.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/net/wireless/intel/iwlwifi/dvm/calib.c b/drivers/net/wireless/intel/iwlwifi/dvm/calib.c
index ae1f0cf560e2..7480c19d7af0 100644
--- a/drivers/net/wireless/intel/iwlwifi/dvm/calib.c
+++ b/drivers/net/wireless/intel/iwlwifi/dvm/calib.c
@@ -18,8 +18,11 @@
 /* Opaque calibration results */
 struct iwl_calib_result {
 	struct list_head list;
-	size_t cmd_len;
-	struct iwl_calib_cmd cmd;
+	DECLARE_FLEX_ARRAY_ELEMENTS_COUNT(size_t, cmd_len);
+	union {
+		struct iwl_calib_cmd cmd;
+		DECLARE_FLEX_ARRAY_ELEMENTS(u8, data);
+	};
 	/* data follows */
 };
 
@@ -59,14 +62,10 @@ int iwl_send_calib_results(struct iwl_priv *priv)
 int iwl_calib_set(struct iwl_priv *priv,
 		  const struct iwl_calib_cmd *cmd, int len)
 {
-	struct iwl_calib_result *res, *tmp;
+	struct iwl_calib_result *res = NULL, *tmp;
 
-	res = kmalloc(sizeof(*res) + len - sizeof(struct iwl_calib_hdr),
-		      GFP_ATOMIC);
-	if (!res)
+	if (len < sizeof(*cmd) || mem_to_flex_dup(&res, cmd, len, GFP_ATOMIC))
 		return -ENOMEM;
-	memcpy(&res->hdr, cmd, len);
-	res->cmd_len = len;
 
 	list_for_each_entry(tmp, &priv->calib_results, list) {
 		if (tmp->cmd.hdr.op_code == res->cmd.hdr.op_code) {
-- 
2.32.0