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From:   Sami Tolvanen <samitolvanen@google.com>
Date:   Fri, 18 Nov 2022 12:27:46 -0800
Message-ID: <CABCJKudPXbDx2MSURDxGanTLhBkJjpMx=G=2RPDi6+96LGxcvw@mail.gmail.com>
Subject: Re: [PATCH v2 08/12] crypto: x86/sm4 - fix crash with CFI enabled
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     x86@kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-crypto@vger.kernel.org
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On Fri, Nov 18, 2022 at 12:10 PM Eric Biggers <ebiggers@kernel.org> wrote:
>
> On Fri, Nov 18, 2022 at 11:44:17AM -0800, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@google.com>
> >
> > sm4_aesni_avx_ctr_enc_blk8(), sm4_aesni_avx_cbc_dec_blk8(),
> > sm4_aesni_avx_cfb_dec_blk8(), sm4_aesni_avx2_ctr_enc_blk16(),
> > sm4_aesni_avx2_cbc_dec_blk16(), and sm4_aesni_avx2_cfb_dec_blk16() are
> > called via indirect function calls.  Therefore they need to use
> > SYM_TYPED_FUNC_START instead of SYM_FUNC_START to cause their type
> > hashes to be emitted when the kernel is built with CONFIG_CFI_CLANG=y.
> > Otherwise, the code crashes with a CFI failure.
> >
> > (Or at least that should be the case.  For some reason the CFI checks in
> > sm4_avx_cbc_decrypt(), sm4_avx_cfb_decrypt(), and sm4_avx_ctr_crypt()
> > are not always being generated, using current tip-of-tree clang.
> > Anyway, this patch is a good idea anyway.)
>
> Sami, is it expected that a CFI check isn't being generated for the indirect
> call to 'func' in sm4_avx_cbc_decrypt()?  I'm using LLVM commit 4a7be42d922af0.

If the compiler emits an indirect call, it should also emit a CFI
check. What's the assembly code it generates here?

Sami