linux-kernel - Re: [PATCH 1/4] media: venus: hfi_parser: add check to avoid out of bound access

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Message-ID: <ndlf4bsijb723cctkvd7hkwmo7plbzr3q2dhqc3tpyujbfcr3z@g4rvg5p7vhfs>
Date: Thu, 7 Nov 2024 12:41:31 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Vikash Garodia <quic_vgarodia@...cinc.com>
Cc: Stanimir Varbanov <stanimir.k.varbanov@...il.com>, 
	Bryan O'Donoghue <bryan.odonoghue@...aro.org>, Mauro Carvalho Chehab <mchehab@...nel.org>, 
	linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	stable@...r.kernel.org
Subject: Re: [PATCH 1/4] media: venus: hfi_parser: add check to avoid out of
 bound access

On Thu, Nov 07, 2024 at 01:47:20PM +0530, Vikash Garodia wrote:
> 
> On 11/5/2024 7:25 PM, Dmitry Baryshkov wrote:
> > On Tue, Nov 05, 2024 at 02:24:54PM +0530, Vikash Garodia wrote:
> >> There is a possibility that init_codecs is invoked multiple times during
> >> manipulated payload from video firmware. In such case, if codecs_count
> >> can get incremented to value more than MAX_CODEC_NUM, there can be OOB
> >> access. Keep a check for max accessible memory before accessing it.
> > 
> > No. Please make sure that init_codecs() does a correct thing, so that
> > core->codecs_count isn't incremented that much (or even better that
> > init_codecs() doesn't do anything if it is executed second time).
> init_codecs() parses the payload received from firmware and . I don't think we
> can control this part when we have something like this from a malicious firmware
> payload
> HFI_PROPERTY_PARAM_CODEC_SUPPORTED
> HFI_PROPERTY_PARAM_CODEC_SUPPORTED
> HFI_PROPERTY_PARAM_CODEC_SUPPORTED
> ...
> Limiting it to second iteration would restrict the functionality when property
> HFI_PROPERTY_PARAM_CODEC_SUPPORTED is sent for supported number of codecs.

If you can have a malicious firmware (which is owned and signed by
Qualcomm / OEM), then you have to be careful and skip duplicates. So
instead of just adding new cap to core->caps, you have to go through
that array, check that you are not adding a duplicate (and report a
[Firmware Bug] for duplicates), check that there is an empty slot, etc.

Just ignoring the "extra" entries is not enough.

> 
> Regards,
> Vikash
> >>
> >> Cc: stable@...r.kernel.org
> >> Fixes: 1a73374a04e5 ("media: venus: hfi_parser: add common capability parser")
> >> Signed-off-by: Vikash Garodia <quic_vgarodia@...cinc.com>
> >> ---
> >>  drivers/media/platform/qcom/venus/hfi_parser.c | 4 ++++
> >>  1 file changed, 4 insertions(+)
> >>
> >> diff --git a/drivers/media/platform/qcom/venus/hfi_parser.c b/drivers/media/platform/qcom/venus/hfi_parser.c
> >> index 3df241dc3a118bcdeb2c28a6ffdb907b644d5653..27d0172294d5154f4839e8cef172f9a619dfa305 100644
> >> --- a/drivers/media/platform/qcom/venus/hfi_parser.c
> >> +++ b/drivers/media/platform/qcom/venus/hfi_parser.c
> >> @@ -23,6 +23,8 @@ static void init_codecs(struct venus_core *core)
> >>  		return;
> >>  
> >>  	for_each_set_bit(bit, &core->dec_codecs, MAX_CODEC_NUM) {
> >> +		if (core->codecs_count >= MAX_CODEC_NUM)
> >> +			return;
> >>  		cap = &caps[core->codecs_count++];
> >>  		cap->codec = BIT(bit);
> >>  		cap->domain = VIDC_SESSION_TYPE_DEC;
> >> @@ -30,6 +32,8 @@ static void init_codecs(struct venus_core *core)
> >>  	}
> >>  
> >>  	for_each_set_bit(bit, &core->enc_codecs, MAX_CODEC_NUM) {
> >> +		if (core->codecs_count >= MAX_CODEC_NUM)
> >> +			return;
> >>  		cap = &caps[core->codecs_count++];
> >>  		cap->codec = BIT(bit);
> >>  		cap->domain = VIDC_SESSION_TYPE_ENC;
> >>
> >> -- 
> >> 2.34.1
> >>
> > 

-- 
With best wishes
Dmitry