linux-kernel - Re: [PATCH v2] media: venus: prevent potential integer overflow in decide

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Message-ID: <41899b79-7b12-4f94-a55a-7d365336a147@linaro.org>
Date: Tue, 7 Oct 2025 12:38:08 +0100
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Pavel Zhigulin <Pavel.Zhigulin@...persky.com>,
 Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>
Cc: Vikash Garodia <vikash.garodia@....qualcomm.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Stanimir Varbanov <stanimir.varbanov@...aro.org>,
 linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH v2] media: venus: prevent potential integer overflow in
 decide_core()

On 07/10/2025 11:30, Pavel Zhigulin wrote:
> The function 'decide_core()' contains the following code:
> 
> 	cur_inst_load = load_per_instance(inst);
> 	cur_inst_load *= inst->clk_data.vpp_freq;
> 	...
> 	cur_inst_lp_load = load_per_instance(inst);
> 	cur_inst_lp_load *= inst->clk_data.low_power_freq;
> 
> This can lead to an integer overflow because the variables
> 'cur_inst_load' and 'cur_inst_lp_load' are of type u32.
> 
> The overflow can occur in the following scenario:
> 
>    1. The current FPS is 240 (VENUS_MAX_FPS constant).
>       The processed image frame has a resolution of 4096x4096 pixels.
>    2. According to 'codec_freq_data':
>         - 'inst->clk_data.low_power_freq' can be up to 320
>         - 'inst->clk_data.vpp_freq' can be up to 675
>       (see drivers/media/platform/qcom/venus/hfi_platform_v4.c
>        and drivers/media/platform/qcom/venus/hfi_platform_v6.c)
>    3. 'load_per_instance()' returns 15728640 under these conditions.
>    4. As a result:
>         cur_inst_load *= inst->clk_data.vpp_freq → 10616832000
>         cur_inst_lp_load *= inst->clk_data.low_power_freq → 5033164800
> 
> The proposed fix changes the type of these variables from u32 to u64
> to prevent overflow.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: 3cfe5815ce0e ("media: venus: Enable low power setting for encoder")
> Signed-off-by: Pavel Zhigulin <Pavel.Zhigulin@...persky.com>
> ---
> v2: Revert min_coreid and min_lp_coreid to u32 as
>      Dikshita Agarwal <dikshita.agarwal@....qualcomm.com> suggested
> 	during review
> v1: https://lore.kernel.org/all/20251006154041.1804800-1-Pavel.Zhigulin@kaspersky.com/
>   drivers/media/platform/qcom/venus/pm_helpers.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/platform/qcom/venus/pm_helpers.c b/drivers/media/platform/qcom/venus/pm_helpers.c
> index f0269524ac70..eec49590e806 100644
> --- a/drivers/media/platform/qcom/venus/pm_helpers.c
> +++ b/drivers/media/platform/qcom/venus/pm_helpers.c
> @@ -582,9 +582,9 @@ static int move_core_to_power_save_mode(struct venus_core *core,
>   }
> 
>   static void
> -min_loaded_core(struct venus_inst *inst, u32 *min_coreid, u32 *min_load, bool low_power)
> +min_loaded_core(struct venus_inst *inst, u32 *min_coreid, u64 *min_load, bool low_power)
>   {
> -	u32 mbs_per_sec, load, core1_load = 0, core2_load = 0;
> +	u64 mbs_per_sec, load, core1_load = 0, core2_load = 0;
>   	u32 cores_max = core_num_max(inst);
>   	struct venus_core *core = inst->core;
>   	struct venus_inst *inst_pos;
> @@ -639,8 +639,9 @@ static int decide_core(struct venus_inst *inst)
>   {
>   	const u32 ptype = HFI_PROPERTY_CONFIG_VIDEOCORES_USAGE;
>   	struct venus_core *core = inst->core;
> -	u32 min_coreid, min_load, cur_inst_load;
> -	u32 min_lp_coreid, min_lp_load, cur_inst_lp_load;
> +	u32 min_coreid, min_lp_coreid;
> +	u64 min_load, cur_inst_load;
> +	u64 min_lp_load, cur_inst_lp_load;
>   	struct hfi_videocores_usage_type cu;
>   	unsigned long max_freq = ULONG_MAX;
>   	struct device *dev = core->dev;
> --
> 2.43.0
> 

Contingent on passing tests.

Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>