2019-08-31 12:05:02

by Daniel Mack

Subject: [PATCH] hw_random: timeriomem_rng: relax check on memory resource size

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 <[email protected]>
---
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

2019-09-05 05:04:48

by Herbert Xu

Subject: Re: [PATCH] hw_random: timeriomem_rng: relax check on memory resource size

On Sat, Aug 31, 2019 at 01:55:55PM +0200, Daniel Mack wrote:
> 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 <[email protected]>
> ---
> Documentation/devicetree/bindings/rng/timeriomem_rng.txt | 2 +-
> drivers/char/hw_random/timeriomem-rng.c | 4 ++--
> 2 files changed, 3 insertions(+), 3 deletions(-)

Patch applied. Thanks.
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt