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From:   Daniel Mack <daniel@zonque.org>
To:     mpm@selenic.com, herbert@gondor.apana.org.au,
        gregkh@linuxfoundation.org
Cc:     linux-crypto@vger.kernel.org, Daniel Mack <daniel@zonque.org>
Subject: [PATCH] hw_random: timeriomem_rng: relax check on memory resource size
Date:   Sat, 31 Aug 2019 13:55:55 +0200
Message-Id: <20190831115555.11708-1-daniel@zonque.org>
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Sender: linux-crypto-owner@vger.kernel.org
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The timeriomem_rng driver only accesses the first 4 bytes of the given
memory area and currently, it also forces that memory resource to be
exactly 4 bytes in size.

This, however, is problematic when used with device-trees that are
generated from things like FPGA toolchains, where the minimum size
of an exposed memory block may be something like 4k.

Hence, let's only check for what's needed for the driver to operate
properly; namely that we have enough memory available to read the
random data from.

Signed-off-by: Daniel Mack <daniel@zonque.org>
---
 Documentation/devicetree/bindings/rng/timeriomem_rng.txt | 2 +-
 drivers/char/hw_random/timeriomem-rng.c                  | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/rng/timeriomem_rng.txt b/Documentation/devicetree/bindings/rng/timeriomem_rng.txt
index 214940093b55..fb4846160047 100644
--- a/Documentation/devicetree/bindings/rng/timeriomem_rng.txt
+++ b/Documentation/devicetree/bindings/rng/timeriomem_rng.txt
@@ -12,7 +12,7 @@ Optional properties:
             which disables using this rng to automatically fill the kernel's
             entropy pool.
 
-N.B. currently 'reg' must be four bytes wide and aligned
+N.B. currently 'reg' must be at least four bytes wide and 32-bit aligned
 
 Example:
 
diff --git a/drivers/char/hw_random/timeriomem-rng.c b/drivers/char/hw_random/timeriomem-rng.c
index f615684028af..dc0194d85d80 100644
--- a/drivers/char/hw_random/timeriomem-rng.c
+++ b/drivers/char/hw_random/timeriomem-rng.c
@@ -120,9 +120,9 @@ static int timeriomem_rng_probe(struct platform_device *pdev)
 	if (!res)
 		return -ENXIO;
 
-	if (res->start % 4 != 0 || resource_size(res) != 4) {
+	if (res->start % 4 != 0 || resource_size(res) < 4) {
 		dev_err(&pdev->dev,
-			"address must be four bytes wide and aligned\n");
+			"address must be at least four bytes wide and 32-bit aligned\n");
 		return -EINVAL;
 	}
 
-- 
2.21.0