Re: [PATCH 0/11] crypto: CFI fixes

Eric Biggers
2022-11-18T18:49:40Z

On Fri, Nov 18, 2022 at 03:43:55PM +0000, Elliott, Robert (Servers) wrote:
>
> > -----Original Message-----
> > From: Eric Biggers <ebiggers@kernel.org>
> > Sent: Friday, November 18, 2022 3:02 AM
> > To: linux-crypto@vger.kernel.org
> > Cc: x86@kernel.org; linux-arm-kernel@lists.infradead.org; Sami Tolvanen
> > <samitolvanen@google.com>
> > Subject: [PATCH 0/11] crypto: CFI fixes
> >
> > This series fixes some crashes when CONFIG_CFI_CLANG (Control Flow
> > Integrity) is enabled, with the new CFI implementation that was merged
> > in 6.1 and is supported on x86. Some of them were unconditional
> > crashes, while others depended on whether the compiler optimized out the
> > indirect calls or not. This series also simplifies some code that was
> > intended to work around limitations of the old CFI implementation and is
> > unnecessary for the new CFI implementation.
>
> Some of the x86 modules EXPORT their asm functions. Does that leave them
> at risk of being called indirectly?
>
> arch/x86/crypto/camellia-aesni-avx-asm_64.S:SYM_FUNC_START(camellia_ecb_dec_16way)
> arch/x86/crypto/camellia-aesni-avx-asm_64.S:SYM_FUNC_START(camellia_ecb_enc_16way)
> arch/x86/crypto/camellia-aesni-avx-asm_64.S:SYM_FUNC_START(camellia_cbc_dec_16way)
> arch/x86/crypto/camellia_aesni_avx_glue.c:asmlinkage void camellia_ecb_enc_16way(const void *ctx, u8 *dst, const u8 *src);
> arch/x86/crypto/camellia_aesni_avx_glue.c:EXPORT_SYMBOL_GPL(camellia_ecb_enc_16way);
> arch/x86/crypto/camellia_aesni_avx_glue.c:asmlinkage void camellia_ecb_dec_16way(const void *ctx, u8 *dst, const u8 *src);
> arch/x86/crypto/camellia_aesni_avx_glue.c:EXPORT_SYMBOL_GPL(camellia_ecb_dec_16way);
> arch/x86/crypto/camellia_aesni_avx_glue.c:asmlinkage void camellia_cbc_dec_16way(const void *ctx, u8 *dst, const u8 *src);
> arch/x86/crypto/camellia_aesni_avx_glue.c:EXPORT_SYMBOL_GPL(camellia_cbc_dec_16way);
>
> arch/x86/crypto/twofish-x86_64-asm_64-3way.S:SYM_FUNC_START(__twofish_enc_blk_3way)
> arch/x86/crypto/twofish.h:asmlinkage void __twofish_enc_blk_3way(const void *ctx, u8 *dst, const u8 *src,
> arch/x86/crypto/twofish_glue_3way.c:EXPORT_SYMBOL_GPL(__twofish_enc_blk_3way);

No, that doesn't matter at all. Whether a symbol is exported or not just has to
do with how the code is divided into modules. It doesn't have anything to do
with indirect calls.

> A few of the x86 asm functions used by C code are not referenced with
> asmlinkage like all the others. They're not EXPORTed, though, so whether
> they're indirectly used can be determined.
>
> u32 crc32_pclmul_le_16(unsigned char const *buffer, size_t len, u32 crc32);
>
> void clmul_ghash_mul(char *dst, const u128 *shash);
>
> void clmul_ghash_update(char *dst, const char *src, unsigned int srclen,
> const u128 *shash);

No, the above functions are only called directly.

I did do another search and found that some of the sm4 functions are called
indirectly, though, so I'll send out an updated patchset that fixes those too.

- Eric