linux-kernel - [PATCH 5/5] crypto: stm32/crc: protect from concurrent accesses

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Date:   Tue, 12 May 2020 16:11:13 +0200
From:   Nicolas Toromanoff <nicolas.toromanoff@...com>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S . Miller" <davem@...emloft.net>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>
CC:     Nicolas Toromanoff <nicolas.toromanoff@...com>,
        <linux-crypto@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH 5/5] crypto: stm32/crc: protect from concurrent accesses

Protect STM32 CRC device from concurrent accesses.

As we create a spinlocked section that increase with buffer size,
we provide a module parameter to release the pressure by splitting
critical section in chunks.

Size of each chunk is defined in burst_size module parameter.
By default burst_size=0, i.e. don't split incoming buffer.

Signed-off-by: Nicolas Toromanoff <nicolas.toromanoff@...com>
---
 drivers/crypto/stm32/stm32-crc32.c | 47 ++++++++++++++++++++++++++++--
 1 file changed, 45 insertions(+), 2 deletions(-)

diff --git a/drivers/crypto/stm32/stm32-crc32.c b/drivers/crypto/stm32/stm32-crc32.c
index 413415c216ef..3ba41148c2a4 100644
--- a/drivers/crypto/stm32/stm32-crc32.c
+++ b/drivers/crypto/stm32/stm32-crc32.c
@@ -35,11 +35,16 @@
 
 #define CRC_AUTOSUSPEND_DELAY	50
 
+static unsigned int burst_size;
+module_param(burst_size, uint, 0644);
+MODULE_PARM_DESC(burst_size, "Select burst byte size (0 unlimited)");
+
 struct stm32_crc {
 	struct list_head list;
 	struct device    *dev;
 	void __iomem     *regs;
 	struct clk       *clk;
+	spinlock_t       lock;
 };
 
 struct stm32_crc_list {
@@ -109,6 +114,7 @@ static int stm32_crc_init(struct shash_desc *desc)
 	struct stm32_crc_desc_ctx *ctx = shash_desc_ctx(desc);
 	struct stm32_crc_ctx *mctx = crypto_shash_ctx(desc->tfm);
 	struct stm32_crc *crc;
+	unsigned long flags;
 
 	crc = stm32_crc_get_next_crc();
 	if (!crc)
@@ -116,6 +122,8 @@ static int stm32_crc_init(struct shash_desc *desc)
 
 	pm_runtime_get_sync(crc->dev);
 
+	spin_lock_irqsave(&crc->lock, flags);
+
 	/* Reset, set key, poly and configure in bit reverse mode */
 	writel_relaxed(bitrev32(mctx->key), crc->regs + CRC_INIT);
 	writel_relaxed(bitrev32(mctx->poly), crc->regs + CRC_POL);
@@ -125,18 +133,21 @@ static int stm32_crc_init(struct shash_desc *desc)
 	/* Store partial result */
 	ctx->partial = readl_relaxed(crc->regs + CRC_DR);
 
+	spin_unlock_irqrestore(&crc->lock, flags);
+
 	pm_runtime_mark_last_busy(crc->dev);
 	pm_runtime_put_autosuspend(crc->dev);
 
 	return 0;
 }
 
-static int stm32_crc_update(struct shash_desc *desc, const u8 *d8,
-			    unsigned int length)
+static int burst_update(struct shash_desc *desc, const u8 *d8,
+			size_t length)
 {
 	struct stm32_crc_desc_ctx *ctx = shash_desc_ctx(desc);
 	struct stm32_crc_ctx *mctx = crypto_shash_ctx(desc->tfm);
 	struct stm32_crc *crc;
+	unsigned long flags;
 
 	crc = stm32_crc_get_next_crc();
 	if (!crc)
@@ -144,6 +155,8 @@ static int stm32_crc_update(struct shash_desc *desc, const u8 *d8,
 
 	pm_runtime_get_sync(crc->dev);
 
+	spin_lock_irqsave(&crc->lock, flags);
+
 	/*
 	 * Restore previously calculated CRC for this context as init value
 	 * Restore polynomial configuration
@@ -182,12 +195,40 @@ static int stm32_crc_update(struct shash_desc *desc, const u8 *d8,
 	/* Store partial result */
 	ctx->partial = readl_relaxed(crc->regs + CRC_DR);
 
+	spin_unlock_irqrestore(&crc->lock, flags);
+
 	pm_runtime_mark_last_busy(crc->dev);
 	pm_runtime_put_autosuspend(crc->dev);
 
 	return 0;
 }
 
+static int stm32_crc_update(struct shash_desc *desc, const u8 *d8,
+			    unsigned int length)
+{
+	const unsigned int burst_sz = burst_size;
+	unsigned int rem_sz;
+	const u8 *cur;
+	size_t size;
+	int ret;
+
+	if (!burst_sz)
+		return burst_update(desc, d8, length);
+
+	/* Digest first bytes not 32bit aligned at first pass in the loop */
+	size = min(length,
+		   burst_sz + (unsigned int)d8 - ALIGN_DOWN((unsigned int)d8,
+							    sizeof(u32)));
+	for (rem_sz = length, cur = d8; rem_sz;
+	     rem_sz -= size, cur += size, size = min(rem_sz, burst_sz)) {
+		ret = burst_update(desc, cur, size);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 static int stm32_crc_final(struct shash_desc *desc, u8 *out)
 {
 	struct stm32_crc_desc_ctx *ctx = shash_desc_ctx(desc);
@@ -300,6 +341,8 @@ static int stm32_crc_probe(struct platform_device *pdev)
 	pm_runtime_irq_safe(dev);
 	pm_runtime_enable(dev);
 
+	spin_lock_init(&crc->lock);
+
 	platform_set_drvdata(pdev, crc);
 
 	spin_lock(&crc_list.lock);
-- 
2.17.1