linux-kernel - Re: [PATCH 5/8] ntb_tool: BUG: Ensure the buffer size is large enough to return all spads

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Message-ID: <CAJ80savw=Lpzpf5VT2X=Uge0XO13nrwmw6SypvhiPgLsK6CLOw@mail.gmail.com>
Date:	Fri, 10 Jun 2016 22:35:51 -0400
From:	Allen Hubbe <allenbh@...il.com>
To:	Logan Gunthorpe <logang@...tatee.com>
Cc:	Jon Mason <jdmason@...zu.us>, Dave Jiang <dave.jiang@...el.com>,
	Shuah Khan <shuahkh@....samsung.com>,
	Sudip Mukherjee <sudipm.mukherjee@...il.com>,
	Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
	linux-ntb@...glegroups.com, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 5/8] ntb_tool: BUG: Ensure the buffer size is large enough
 to return all spads

On Fri, Jun 10, 2016 at 6:54 PM, Logan Gunthorpe <logang@...tatee.com> wrote:
> On hardware with 32 scratchpad registers the spad field in ntb tool
> could chop off the end. The maximum buffer size is increased from
> 256 to 15 times the number or scratchpads.
>
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>

It could be marginally better if there was an explanation to accompany
the magic number 15, but it's not a big deal.  One might guess it has
something to do with the expected length of the formatted string.

Acked-by: Allen Hubbe <Allen.Hubbe@....com>

> ---
>  drivers/ntb/test/ntb_tool.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/ntb/test/ntb_tool.c b/drivers/ntb/test/ntb_tool.c
> index 4c01057..954e1d5 100644
> --- a/drivers/ntb/test/ntb_tool.c
> +++ b/drivers/ntb/test/ntb_tool.c
> @@ -368,7 +368,9 @@ static ssize_t tool_spadfn_read(struct tool_ctx *tc, char __user *ubuf,
>         if (!spad_read_fn)
>                 return -EINVAL;
>
> -       buf_size = min_t(size_t, size, 0x100);
> +       spad_count = ntb_spad_count(tc->ntb);
> +
> +       buf_size = min_t(size_t, size, spad_count * 15);
>
>         buf = kmalloc(buf_size, GFP_KERNEL);
>         if (!buf)
> @@ -376,7 +378,6 @@ static ssize_t tool_spadfn_read(struct tool_ctx *tc, char __user *ubuf,
>
>         pos = 0;
>
> -       spad_count = ntb_spad_count(tc->ntb);
>         for (i = 0; i < spad_count; ++i) {
>                 pos += scnprintf(buf + pos, buf_size - pos, "%d\t%#x\n",
>                                  i, spad_read_fn(tc->ntb, i));
> --
> 2.1.4
>
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