linux-kernel - Re: [PATCH] misc: fastrpc: fix potential fastrpc_invoke

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Message-ID: <da155fca-98b9-f65e-1683-314a132a8255@linaro.org>
Date:   Tue, 12 May 2020 11:42:20 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     gregkh@...uxfoundation.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, arnd@...db.de,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH] misc: fastrpc: fix potential fastrpc_invoke_ctx leak



On 12/05/2020 02:18, Bjorn Andersson wrote:
> On Mon 11 May 09:29 PDT 2020, Srinivas Kandagatla wrote:
> 
>> fastrpc_invoke_ctx can have refcount of 2 in error path where
>> rpmsg_send() fails to send invoke message. decrement the refcount
>> properly in the error path to fix this leak.
>>
>> This also fixes below static checker warning:
>>
>> drivers/misc/fastrpc.c:990 fastrpc_internal_invoke()
>> warn: 'ctx->refcount.refcount.ref.counter' not decremented on lines: 990.
>>
>> Fixes: c68cfb718c8f ("misc: fastrpc: Add support for context")
>> Reported-by: Dan Carpenter<dan.carpenter@...cle.com>
>> Signed-off-by: Srinivas Kandagatla<srinivas.kandagatla@...aro.org>
>> ---
>>   drivers/misc/fastrpc.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
>> index 9065d3e71ff7..07065728e39f 100644
>> --- a/drivers/misc/fastrpc.c
>> +++ b/drivers/misc/fastrpc.c
>> @@ -949,8 +949,10 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
>>   	dma_wmb();
>>   	/* Send invoke buffer to remote dsp */
>>   	err = fastrpc_invoke_send(fl->sctx, ctx, kernel, handle);
>> -	if (err)
>> +	if (err) {
>> +		fastrpc_context_put(ctx);
> So we refcount ctx once for the invoke function and once between send
> and callback. And this fastrpc_context_put() would counter the fact that
> rpmsg_send() failed, so we will not get the "remote's" put().
> 
> I think that if you moved this call inside fastrpc_invoke_send() it's
> relationship to the failing rpmsg_send() would be obvious.

That works as well, and sounds much cleaner!


thanks,
srini

> 
> Regards,