tls: Avoid -Wflex-array-member-not-at-end warning

Remove unused flexible-array member in struct tls_rec and, with this, fix the following warning:

net/tls/tls.h:131:29: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Also, add a comment to prevent people from adding any members after struct aead_request, which is a flexible structure --this is a structure that ends in a flexible-array member.

---
Changes in v2:
- Remove unused flex array. (Sabrina Dubroca).
- Update changelog text.

v1:
- Link: https://lore.kernel.org/linux-hardening/aNFfmBLEoDSBSLJe@kspp/

 net/tls/tls.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

index 4e077068e6d9..06d462c57284 100644
@@ -128,8 +128,9 @@ struct tls_rec {
 
 	char aad_space[TLS_AAD_SPACE_SIZE];
 	u8 iv_data[TLS_MAX_IV_SIZE];
+
+	/* Must be last --ends in a flexible-array member. */
 	struct aead_request aead_req;
-	u8 aead_req_ctx[];
 };
 
 int __net_init tls_proc_init(struct net *net);

2.43.0

Thanks for the updated patch.

A process nit: the correct subject prefix for this type of work within networking would be [PATCH net-next v2] (indicating it targets the "net-next" tree).

Once that warning is enabled, re-adding a field after aead_req will not be allowed by the compiler, right? The comment is probably not really needed, but since there are "must be first" comments all over include/net, I guess it's useful.

Sabrina