From: Sascha Hauer <sha@pengutronix.de>
To: Ahmad Fatoum <ahmad@a3f.at>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH master] fs: /dev/mem: handle copy at offset 0 correctly
Date: Tue, 7 Dec 2021 10:13:05 +0100 [thread overview]
Message-ID: <20211207091305.GL28260@pengutronix.de> (raw)
In-Reply-To: <20211129071454.2014315-1-ahmad@a3f.at>
On Mon, Nov 29, 2021 at 08:14:54AM +0100, Ahmad Fatoum wrote:
> Despite that /dev/mem has a size of 0, the check preventing
> out-of-bounds access works for /dev/mem as well, because of unsigned
> wrap around. Corner case is when offset is zero. There will be no wrap
> around and
>
> count = min(count, 0 - 0) = 0
>
> Leading to unexpected behavior with e.g.
>
> memcmp -s /dev/mem 0
>
> on systems without MMU. Fix this.
>
> Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
> ---
> fs/devfs-core.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
Applied, thanks
Sascha
>
> diff --git a/fs/devfs-core.c b/fs/devfs-core.c
> index 3715e543e632..2d016e0e4861 100644
> --- a/fs/devfs-core.c
> +++ b/fs/devfs-core.c
> @@ -573,7 +573,10 @@ ssize_t mem_copy(struct device_d *dev, void *dst, const void *src,
> if (!dev || dev->num_resources < 1)
> return -1;
>
> - count = size = min(count, resource_size(&dev->resource[0]) - offset);
> + if (resource_size(&dev->resource[0]) > 0 || offset != 0)
> + count = min(count, resource_size(&dev->resource[0]) - offset);
> +
> + size = count;
>
> /* no rwsize specification given. Do whatever memcpy likes best */
> if (!rwsize) {
> --
> 2.33.0
>
>
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prev parent reply other threads:[~2021-12-07 9:16 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-29 7:14 Ahmad Fatoum
2021-12-07 9:13 ` Sascha Hauer [this message]
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