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

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Date:   Fri,  1 Jul 2022 13:27:35 +0000
From:   Corentin Labbe <clabbe@...libre.com>
To:     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,
        Corentin Labbe <clabbe@...libre.com>
Subject: [RFC PATCH] crypto: flush poison data

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? */
-- 
2.35.1