linux-kernel - Re: [PATCH v3] misc: fastrpc: fix improper packet size calculation

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Message-ID: <3c4659fff3c632373d7df4712a3c0311@codeaurora.org>
Date:   Tue, 23 Nov 2021 11:42:12 +0530
From:   jeyr@...eaurora.org
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     linux-arm-msm@...r.kernel.org, srinivas.kandagatla@...aro.org,
        linux-kernel@...r.kernel.org, fastrpc.upstream@....qualcomm.com
Subject: Re: [PATCH v3] misc: fastrpc: fix improper packet size calculation

On 2021-11-19 18:23, Greg KH wrote:
> On Fri, Nov 19, 2021 at 06:19:27PM +0530, jeyr@...eaurora.org wrote:
>> On 2021-09-21 18:43, jeyr@...eaurora.org wrote:
>> > On 2021-09-21 18:10, Greg KH wrote:
>> > > On Tue, Sep 21, 2021 at 06:03:42PM +0530, jeyr@...eaurora.org wrote:
>> > > > On 2021-09-21 17:22, Greg KH wrote:
>> > > > > On Tue, Sep 21, 2021 at 05:18:15PM +0530, Jeya R wrote:
>> > > > > > The buffer list is sorted and this is not being considered while
>> > > > > > calculating packet size. This would lead to improper copy length
>> > > > > > calculation for non-dmaheap buffers which would eventually cause
>> > > > > > sending improper buffers to DSP.
>> > > > > >
>> > > > > > Fixes: c68cfb718c8f ("misc: fastrpc: Add support for context Invoke
>> > > > > > method")
>> > > > > > Signed-off-by: Jeya R <jeyr@...eaurora.org>
>> > > > > > Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>> > > > >
>> > > > > Does this also need to go to the stable kernels?
>> > > > Yes, this needs to go to stable kernels also as this fixes a
>> > > > potential issue
>> > > > which is easily reproducible.
>> > >
>> > >
>> > >
>> > > >
>> > > > >
>> > > > > > ---
>> > > > > > Changes in v3:
>> > > > > > - relocate patch change list
>> > > > > >
>> > > > > > Changes in v2:
>> > > > > > - updated commit message to proper format
>> > > > > > - added fixes tag to commit message
>> > > > > > - removed unnecessary variable initialization
>> > > > > > - removed length check during payload calculation
>> > > > > >
>> > > > > >  drivers/misc/fastrpc.c | 10 ++++++----
>> > > > > >  1 file changed, 6 insertions(+), 4 deletions(-)
>> > > > > >
>> > > > > > diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
>> > > > > > index beda610..69d45c4 100644
>> > > > > > --- a/drivers/misc/fastrpc.c
>> > > > > > +++ b/drivers/misc/fastrpc.c
>> > > > > > @@ -719,16 +719,18 @@ static int fastrpc_get_meta_size(struct
>> > > > > > fastrpc_invoke_ctx *ctx)
>> > > > > >  static u64 fastrpc_get_payload_size(struct fastrpc_invoke_ctx *ctx,
>> > > > > > int metalen)
>> > > > > >  {
>> > > > > >  	u64 size = 0;
>> > > > > > -	int i;
>> > > > > > +	int oix;
>> > > > >
>> > > > > What does "oix" stand for?  What was wrong with i?
>> > > > It is just a general convention we use. "oix" is used to iterate
>> > > > through
>> > > > sorted overlap buffer list and use "i" to get corresponding
>> > > > unsorted list
>> > > > index. We follow the same convention at other places also, for
>> > > > example:
>> > > > fastrpc_get_args function.
>> > >
>> > > That is the only place it is used in all of the whole kernel tree.  It
>> > > is not a normal variable for a loop, so who is "we" here?
>> > The convention was followed for the same file(fastrpc.c). As part of
>> > fastrpc_get_args
>> > function, while iterating through sorted buffer list, oix is used as
>> > index and to
>> > get unsorted index "raix", it is using "i". Just following the same way
>> > here to
>> > have better understanding. Please let me know if this is a concern, it
>> > can be updated
>> > to "i", "j" etc.
>> >
>> > -- Thanks
>> > >
>> > > thanks,
>> > >
>> > > greg k-h
>> Hello Greg,
>> 
>> Is this bug-fix patch planned to be released?
> 
> Released in what way?
By release, I mean picked to your misc driver git tree.
> 
> I do not see it in any tree anywhere, perhaps it needs to be 
> resubmitted
> to be accepted?
Sure, will resubmit the patch. Thanks.
> 
> thanks,
> 
> greg k-h