CVE-2026-80522: crypto: tegra - fix rctx->cryptlen calculation in tegra_gcm_do_one_req()

In the Linux kernel, the following vulnerability has been resolved:

crypto: tegra - fix rctx->cryptlen calculation in tegragcmdoonereq()

Perform rctx->cryptlen calculation in tegragcmdoonereq() the same way it is done in tegraccmcryptinit(). The current formulae may lead to a crash if a caller does not call tegragcmsetauthsize() and so ctx->authsize remains zero. Then a decrypt operation with incorrect rctx->cryptlen will lead to a write beyound rctx->dstsg buffer.

As a follow-up cleanup delete struct tegraaeadctx->authsize field since it appears to be completely unused. Also simplify tegraccmsetauthsize() and tegragcmsetauthsize() functions respectively.