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

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Date:	Sat, 11 Jun 2016 09:29:05 -0600
From:	Logan Gunthorpe <logang@...tatee.com>
To:	Allen Hubbe <allenbh@...il.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

Ok, I'll add a comment.

Logan

On 10/06/16 08:35 PM, Allen Hubbe wrote:
> 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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