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

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Date:   Tue, 5 Jul 2022 10:21:13 +0200
From:   LABBE Corentin <clabbe@...libre.com>
To:     Ben Dooks <ben.dooks@...ethink.co.uk>
Cc:     herbert@...dor.apana.org.au, hch@....de, heiko@...ech.de,
        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

Le Fri, Jul 01, 2022 at 02:35:41PM +0100, Ben Dooks a écrit :
> 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?
> 

I just copied what did drivers/crypto/xilinx/zynqmp-sha.c.
I tried to do flush_dcache_range() but it seems to not be implemented on riscV.
And flush_dcache_page(virt_to_page(addr), len) produce a kernel panic.

Any advice on how to go further ?