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

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Date:   Fri, 19 Nov 2021 18:19:27 +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 2021-09-21 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?

-- Thanks