linux-hardening - [PATCH][next] iavf: Replace one-element array in struct virtchnl_rss

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Message-ID: <20210525231851.GA176647@embeddedor>
Date:   Tue, 25 May 2021 18:18:51 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] iavf: Replace one-element array in struct
 virtchnl_rss_key

There is a regular need in the kernel to provide a way to declare having a
dynamically sized set of trailing elements in a structure. Kernel code
should always use “flexible array members”[1] for these cases. The older
style of one-element or zero-length arrays should no longer be used[2].

Refactor the code according to the use of a flexible-array member in struct
virtchnl_rss_key instead of one-element array, and use the struct_size()
helper.

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays

Link: https://github.com/KSPP/linux/issues/79
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/net/ethernet/intel/iavf/iavf_virtchnl.c | 5 ++---
 include/linux/avf/virtchnl.h                    | 6 +++---
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/intel/iavf/iavf_virtchnl.c b/drivers/net/ethernet/intel/iavf/iavf_virtchnl.c
index 167955094170..6f2a4c8beb0b 100644
--- a/drivers/net/ethernet/intel/iavf/iavf_virtchnl.c
+++ b/drivers/net/ethernet/intel/iavf/iavf_virtchnl.c
@@ -799,7 +799,7 @@ void iavf_set_hena(struct iavf_adapter *adapter)
 void iavf_set_rss_key(struct iavf_adapter *adapter)
 {
 	struct virtchnl_rss_key *vrk;
-	int len;
+	size_t len;
 
 	if (adapter->current_op != VIRTCHNL_OP_UNKNOWN) {
 		/* bail because we already have a command pending */
@@ -807,8 +807,7 @@ void iavf_set_rss_key(struct iavf_adapter *adapter)
 			adapter->current_op);
 		return;
 	}
-	len = sizeof(struct virtchnl_rss_key) +
-	      (adapter->rss_key_size * sizeof(u8)) - 1;
+	len = struct_size(vrk, key, adapter->rss_key_size);
 	vrk = kzalloc(len, GFP_KERNEL);
 	if (!vrk)
 		return;
diff --git a/include/linux/avf/virtchnl.h b/include/linux/avf/virtchnl.h
index 9b9d79c270b1..d2fd847a3880 100644
--- a/include/linux/avf/virtchnl.h
+++ b/include/linux/avf/virtchnl.h
@@ -484,10 +484,10 @@ VIRTCHNL_CHECK_STRUCT_LEN(4, virtchnl_promisc_info);
 struct virtchnl_rss_key {
 	u16 vsi_id;
 	u16 key_len;
-	u8 key[1];         /* RSS hash key, packed bytes */
+	u8 key[];         /* RSS hash key, packed bytes */
 };
 
-VIRTCHNL_CHECK_STRUCT_LEN(6, virtchnl_rss_key);
+VIRTCHNL_CHECK_STRUCT_LEN(4, virtchnl_rss_key);
 
 struct virtchnl_rss_lut {
 	u16 vsi_id;
@@ -1079,7 +1079,7 @@ virtchnl_vc_validate_vf_msg(struct virtchnl_version_info *ver, u32 v_opcode,
 		if (msglen >= valid_len) {
 			struct virtchnl_rss_key *vrk =
 				(struct virtchnl_rss_key *)msg;
-			valid_len += vrk->key_len - 1;
+			valid_len += vrk->key_len;
 		}
 		break;
 	case VIRTCHNL_OP_CONFIG_RSS_LUT:
-- 
2.27.0