linux-kernel - Re: [RFC PATCH] crypto: flush poison data

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Message-ID: <4570f6d8-251f-2cdb-1ea6-c3a8d6bb9fcf@codethink.co.uk>
Date:   Fri, 1 Jul 2022 14:35:41 +0100
From:   Ben Dooks <ben.dooks@...ethink.co.uk>
To:     Corentin Labbe <clabbe@...libre.com>, herbert@...dor.apana.org.au,
        hch@....de, heiko@...ech.de
Cc:     linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-sunxi@...ts.linux.dev
Subject: Re: [RFC PATCH] crypto: flush poison data

On 01/07/2022 14:27, Corentin Labbe wrote:
> On my Allwinner D1 nezha, the sun8i-ce fail self-tests due to:
> alg: skcipher: cbc-des3-sun8i-ce encryption overran dst buffer on test vector 0
> 
> In fact the buffer is not overran by device but by the dma_map_single() operation.
> 
> To prevent any corruption of the poisoned data, simply flush them before
> giving the buffer to the tested driver.
> 
> Signed-off-by: Corentin Labbe <clabbe@...libre.com>
> ---
> 
> Hello
> 
> I put this patch as RFC, since this behavour happen only on non yet merged RISCV code.
> (Mostly riscv: implement Zicbom-based CMO instructions + the t-head variant)
> 
> Regards
> 
>   crypto/testmgr.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/crypto/testmgr.c b/crypto/testmgr.c
> index c59bd9e07978..187163e2e593 100644
> --- a/crypto/testmgr.c
> +++ b/crypto/testmgr.c
> @@ -19,6 +19,7 @@
>   #include <crypto/aead.h>
>   #include <crypto/hash.h>
>   #include <crypto/skcipher.h>
> +#include <linux/cacheflush.h>
>   #include <linux/err.h>
>   #include <linux/fips.h>
>   #include <linux/module.h>
> @@ -205,6 +206,8 @@ static void testmgr_free_buf(char *buf[XBUFSIZE])
>   static inline void testmgr_poison(void *addr, size_t len)
>   {
>   	memset(addr, TESTMGR_POISON_BYTE, len);
> +	/* Be sure data is written to prevent corruption from some DMA sync */
> +	flush_icache_range((unsigned long)addr, (unsigned long)addr + len);
>   }
>   
>   /* Is the memory region still fully poisoned? */

why are you flushing the instruction cache and not the data-cache?

-- 
Ben Dooks				http://www.codethink.co.uk/
Senior Engineer				Codethink - Providing Genius

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