Re: [PATCH][next] tls: Use size_add() in call to struct_size()

[Kees Cook]

On Fri, Sep 15, 2023 at 01:12:38PM -0600, Gustavo A. R. Silva wrote:
> If, for any reason, the open-coded arithmetic causes a wraparound,
> the protection that `struct_size()` adds against potential integer
> overflows is defeated. Fix this by hardening call to `struct_size()`
> with `size_add()`.
> 
> Fixes: b89fec54fd61 ("tls: rx: wrap decrypt params in a struct")
> Signed-off-by: Gustavo A. R. Silva 

Reviewed-by: Kees Cook 

-- 
Kees Cook

[PATCH][next] tls: Use size_add() in call to struct_size()

[Gustavo A. R. Silva]

If, for any reason, the open-coded arithmetic causes a wraparound,
the protection that `struct_size()` adds against potential integer
overflows is defeated. Fix this by hardening call to `struct_size()`
with `size_add()`.

Fixes: b89fec54fd61 ("tls: rx: wrap decrypt params in a struct")
Signed-off-by: Gustavo A. R. Silva 
---
 net/tls/tls_sw.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index d1fc295b83b5..270712b8d391 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -1487,7 +1487,7 @@ static int tls_decrypt_sg(struct sock *sk, struct 
iov_iter *out_iov,
 */
aead_size = sizeof(*aead_req) + crypto_aead_reqsize(ctx->aead_recv);
aead_size = ALIGN(aead_size, __alignof__(*dctx));
-   mem = kmalloc(aead_size + struct_size(dctx, sg, n_sgin + n_sgout),
+   mem = kmalloc(aead_size + struct_size(dctx, sg, size_add(n_sgin, 
n_sgout)),
  sk->sk_allocation);
if (!mem) {
err = -ENOMEM;
-- 
2.34.1