From: Ross Philipson <ross.philipson@gmail.com>
To: Wei Liu <wei.liu2@citrix.com>
Cc: "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: [PATCH] blktap2: Invalid logic detecting unaligned buffers in vhd_write_block
Date: Fri, 25 Mar 2016 12:34:29 -0400 [thread overview]
Message-ID: <56F56895.6040006@gmail.com> (raw)
In-Reply-To: <20160325161106.GB21910@citrix.com>
On 03/25/2016 12:11 PM, Wei Liu wrote:
> On Thu, Mar 17, 2016 at 06:10:59PM -0400, Ross Philipson wrote:
>> It seems the logic is meant to detect sector unaligned buffers for block
>> writes. The NOTing of the logic instead masks off any unaligned bits and
>> also would cause the function to always fail. It seems the function is not
>> used in any of the tools so that is probably why the problem is not seen.
>> In the vhd_read_block function it is correct.
>>
>> Signed-off-by: Ross Philipson <ross.philipson@ainfosec.com>
>
> This seems to fall under tools umbrella. I've look at blktap2 code,
> the reasoning is convincing to me so:
>
> Acked-by: Wei Liu <wei.liu2@citrix.com>
>
> But I've never used blktap2 and we don't normally test it so I would
> also wait a bit longer to see if anybody objects to this change.
>
> OOI if no code was using this, how did you discover this problem?
We have an old fork of blktap2 from way back when. I was working to extract our
changes and turn them into patches so we could rebase on upstream blktap2.
Someone long ago found that - I have no idea how but it was a valid fix so I
upstreamed it.
There are a number of other ones that were found that are still in upstream
blktap2 - I plan to send them too.
>
> Wei.
>
>> ---
>> diff --git a/tools/blktap2/vhd/lib/libvhd.c b/tools/blktap2/vhd/lib/libvhd.c
>> index 1fd5b4e..4ebe012 100644
>> --- a/tools/blktap2/vhd/lib/libvhd.c
>> +++ b/tools/blktap2/vhd/lib/libvhd.c
>> @@ -2188,7 +2188,7 @@ vhd_write_block(vhd_context_t *ctx, uint32_t block, char *data)
>> if (block >= ctx->bat.entries)
>> return -ERANGE;
>>
>> - if ((unsigned long)data & ~(VHD_SECTOR_SIZE -1))
>> + if ((unsigned long)data & (VHD_SECTOR_SIZE -1))
>> return -EINVAL;
>>
>> blk = ctx->bat.bat[block];
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xen.org
>> http://lists.xen.org/xen-devel
--
Ross Philipson
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
next prev parent reply other threads:[~2016-03-25 16:34 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-17 22:10 [PATCH] blktap2: Invalid logic detecting unaligned buffers in vhd_write_block Ross Philipson
2016-03-25 16:11 ` Wei Liu
2016-03-25 16:34 ` Ross Philipson [this message]
2016-03-25 16:38 ` Wei Liu
2016-03-29 11:26 ` George Dunlap
2016-03-30 14:47 ` Ross Philipson
2016-04-06 16:51 ` Ross Philipson
2016-07-06 13:16 ` George Dunlap
2016-04-06 14:39 ` Ian Jackson
2016-04-06 15:25 ` Ross Philipson
2016-04-06 15:37 ` Ross Philipson
2016-04-07 16:37 ` Ian Jackson
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