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[PATCH 1/2] crypto: stm32 - Fix uninitialized data usage

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  [PATCH 1/2] crypto: stm32 - Fix uninitialized data usage Arnd Bergmann <arnd@arndb.de> - 2017-09-12 11:40 +0200
    [PATCH 2/2] crypto: stm32 - Try to fix hash padding Arnd Bergmann <arnd@arndb.de> - 2017-09-12 11:40 +0200
    Re: [PATCH 1/2] crypto: stm32 - Fix uninitialized data usage Lionel DEBIEVE <lionel.debieve@st.com> - 2017-09-18 11:40 +0200

#1730785 — [PATCH 1/2] crypto: stm32 - Fix uninitialized data usage

The error handling in stm32_hash_irq_thread passes
uninitialized data into stm32_hash_finish_req, as gcc
points out:

drivers/crypto/stm32/stm32-hash.c: In function 'stm32_hash_irq_thread':
drivers/crypto/stm32/stm32-hash.c:1088:2: error: 'err' may be used uninitialized in this function [-Werror=maybe-uninitialized]

I could not tell what data should be passed there instead,
so this changes the code to always pass zero, making it
well-defined, though possibly still wrong. Please check.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/crypto/stm32/stm32-hash.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/crypto/stm32/stm32-hash.c b/drivers/crypto/stm32/stm32-hash.c
index b585ce54a802..3c23a23e9ee5 100644
--- a/drivers/crypto/stm32/stm32-hash.c
+++ b/drivers/crypto/stm32/stm32-hash.c
@@ -1067,7 +1067,6 @@ static int stm32_hash_cra_sha256_init(struct crypto_tfm *tfm)
 static irqreturn_t stm32_hash_irq_thread(int irq, void *dev_id)
 {
 	struct stm32_hash_dev *hdev = dev_id;
-	int err;
 
 	if (HASH_FLAGS_CPU & hdev->flags) {
 		if (HASH_FLAGS_OUTPUT_READY & hdev->flags) {
@@ -1085,7 +1084,7 @@ static irqreturn_t stm32_hash_irq_thread(int irq, void *dev_id)
 
 finish:
 	/*Finish current request */
-	stm32_hash_finish_req(hdev->req, err);
+	stm32_hash_finish_req(hdev->req, 0);
 
 	return IRQ_HANDLED;
 }
-- 
2.9.0

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#1730786 — [PATCH 2/2] crypto: stm32 - Try to fix hash padding

gcc warns that the length for the extra unaligned data in the hash
function may be used unaligned. In theory this could happen if
we pass a zero-length sg_list, or if sg_is_last() was never true:

In file included from drivers/crypto/stm32/stm32-hash.c:23:
drivers/crypto/stm32/stm32-hash.c: In function 'stm32_hash_one_request':
include/uapi/linux/kernel.h:12:49: error: 'ncp' may be used uninitialized in this function [-Werror=maybe-uninitialized]
 #define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))

Neither of these can happen in practice, so the warning is harmless.

However while trying to suppress the warning, I noticed multiple
problems with that code:

- On big-endian kernels, we byte-swap the data like we do for
  register accesses, however this is a data stream and almost
  certainly needs to use a single writesl() instead of series
  of writel() to give the correct hash.

- If the length is not a multiple of four bytes, we skip the
  last word entirely, since we write the truncated length
  using stm32_hash_set_nblw().

- If we change the code to round the length up rather than
  down, the last bytes contain stale data, so it needs some
  form of padding.

This tries to address all four problems, by correctly
initializing the length to zero, using endian-safe copy
functions, adding zero-padding and passing the padded length.

I have done no testing on this patch, so please review
carefully and if possible test with an unaligned length
and big-endian kernel builds.

Fixes: 8a1012d3f2ab ("crypto: stm32 - Support for STM32 HASH module")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/crypto/stm32/stm32-hash.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/crypto/stm32/stm32-hash.c b/drivers/crypto/stm32/stm32-hash.c
index 3c23a23e9ee5..b2ed2bccdb66 100644
--- a/drivers/crypto/stm32/stm32-hash.c
+++ b/drivers/crypto/stm32/stm32-hash.c
@@ -553,9 +553,9 @@ static int stm32_hash_dma_send(struct stm32_hash_dev *hdev)
 {
 	struct stm32_hash_request_ctx *rctx = ahash_request_ctx(hdev->req);
 	struct scatterlist sg[1], *tsg;
-	int err = 0, len = 0, reg, ncp;
+	int err = 0, len = 0, reg, ncp = 0;
 	unsigned int i;
-	const u32 *buffer = (const u32 *)rctx->buffer;
+	u32 *buffer = (void *)rctx->buffer;
 
 	rctx->sg = hdev->req->src;
 	rctx->total = hdev->req->nbytes;
@@ -620,10 +620,13 @@ static int stm32_hash_dma_send(struct stm32_hash_dev *hdev)
 		reg |= HASH_CR_DMAA;
 		stm32_hash_write(hdev, HASH_CR, reg);
 
-		for (i = 0; i < DIV_ROUND_UP(ncp, sizeof(u32)); i++)
-			stm32_hash_write(hdev, HASH_DIN, buffer[i]);
-
-		stm32_hash_set_nblw(hdev, ncp);
+		if (ncp) {
+			memset(buffer + ncp, 0,
+			       DIV_ROUND_UP(ncp, sizeof(u32)) - ncp);
+			writesl(hdev->io_base + HASH_DIN, buffer,
+				DIV_ROUND_UP(ncp, sizeof(u32)));
+		}
+		stm32_hash_set_nblw(hdev, DIV_ROUND_UP(ncp, sizeof(u32)));
 		reg = stm32_hash_read(hdev, HASH_STR);
 		reg |= HASH_STR_DCAL;
 		stm32_hash_write(hdev, HASH_STR, reg);
-- 
2.9.0

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#1733925

Hi Arnd,

I've already push this fix for review last month, waiting the ack.

"
From: Lionel Debieve <lionel.debieve@st.com>
To: Herbert Xu <herbert@gondor.apana.org.au>, "David S . Miller"
	<davem@davemloft.net>, Maxime Coquelin <mcoquelin.stm32@gmail.com>, Alexandre
  Torgue <alexandre.torgue@st.com>, <linux-crypto@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>, <linux-kernel@vger.kernel.org>
CC: Benjamin Gaignard <benjamin.gaignard@st.com>, Fabien Dessenne
	<fabien.dessenne@st.com>, Ludovic Barre <ludovic.barre@st.com>
Subject: [PATCH 1/1] crypto: stm32/hash - Remove uninitialized symbol
Date: Fri, 18 Aug 2017 15:54:01 +0200
"

Sorry if you receive this mail twice, I didn't see any mail in the mailing list, maybe server issue.

I'm reviewing your second part patch.

BR,

Lionel

> On 09/12/2017 11:35 AM, Arnd Bergmann wrote:
>> The error handling in stm32_hash_irq_thread passes
>> uninitialized data into stm32_hash_finish_req, as gcc
>> points out:
>> drivers/crypto/stm32/stm32-hash.c: In function 'stm32_hash_irq_thread':
>> drivers/crypto/stm32/stm32-hash.c:1088:2: error: 'err' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>> I could not tell what data should be passed there instead,
>> so this changes the code to always pass zero, making it
>> well-defined, though possibly still wrong. Please check.
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>> ---
>>    drivers/crypto/stm32/stm32-hash.c | 3 +--
>>    1 file changed, 1 insertion(+), 2 deletions(-)
>> diff --git a/drivers/crypto/stm32/stm32-hash.c b/drivers/crypto/stm32/stm32-hash.c
>> index b585ce54a802..3c23a23e9ee5 100644
>> --- a/drivers/crypto/stm32/stm32-hash.c
>> +++ b/drivers/crypto/stm32/stm32-hash.c
>> @@ -1067,7 +1067,6 @@ static int stm32_hash_cra_sha256_init(struct crypto_tfm *tfm)
>>    static irqreturn_t stm32_hash_irq_thread(int irq, void *dev_id)
>>    {
>>        struct stm32_hash_dev *hdev = dev_id;
>> -    int err;
>>    
>>        if (HASH_FLAGS_CPU & hdev->flags) {
>>            if (HASH_FLAGS_OUTPUT_READY & hdev->flags) {
>> @@ -1085,7 +1084,7 @@ static irqreturn_t stm32_hash_irq_thread(int irq, void *dev_id)
>>    
>>    finish:
>>        /*Finish current request */
>> -    stm32_hash_finish_req(hdev->req, err);
>> +    stm32_hash_finish_req(hdev->req, 0);
>>    
>>        return IRQ_HANDLED;
>>    }
>

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