Re: MMIO write access to an invalid page in i40e_clear_hw()

[Przemek Kitszel <przemyslaw.kitszel@intel.com>]

On 3/3/25 11:19, Kyungwook Boo wrote:
> Hello,
> 
> It seems that there are invalid page MMIO write access in i40e_clear_hw()

Hi,

is this something that actually occurred, or just a theoretical bug?
(depending on that we will apply it to different tree)

please send a proper patch anyway, as it looks legit to don't go bananas
when HW gives you 0

(and CC netdev instead of generic kernel ML, perhaps that's the reason
this mail was tagged as spam for me)

> due to an integer underflow from num_pf_int(also num_vf_int seems possible).
> 
> The following is a sample code in i40e_clear_hw():
> 
> val = rd32(hw, I40E_GLPCI_CNF2); // (1)
> num_pf_int = FIELD_GET(I40E_GLPCI_CNF2_MSI_X_PF_N_MASK, val); // (2)
> num_vf_int = FIELD_GET(I40E_GLPCI_CNF2_MSI_X_VF_N_MASK, val);
> ...
> for (i = 0; i < num_pf_int - 2; i++)      // (3)
> 	wr32(hw, I40E_PFINT_DYN_CTLN(i), val);  // (4)
> ...
> for (i = 0; i < num_pf_int - 2; i++)			// (5)
> 	wr32(hw, I40E_PFINT_LNKLSTN(i), val);
> ...
> for (i = 0; i < num_vf_int - 2; i++)			// (6)
> 	wr32(hw, I40E_VPINT_LNKLSTN(i), val);
> 
> An example scenario for num_pf_int:
> (1) val = 0 (if MMIO read value was 0)
> (2) num_pf_int = 0 (also zero after bit field extraction from val)
> (3) An integer underflow occurs (num_pf_int - 2 == 0xfffffffe)
> (4) Out-of-bounds MMIO write access if access address exceeds the expected
> range.
> 
>  From above example scenario, the maximum access offset value can be around
> 0x4000347f8(=172G) which seems like this underflow is not intended(also there
> are masking operations like (2) for num_pf_int), so I report this issue.
> 
> I think similar issue also could happen at (5) and (6).
> 
> The following is the patch method I propose:
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_common.c b/drivers/net/ethernet/intel/i40e/i40e_common.c
> index 370b4bddee44..97ef79be39b3 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_common.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_common.c
> @@ -848,19 +848,25 @@ void i40e_clear_hw(struct i40e_hw *hw)
>   	/* stop all the interrupts */
>   	wr32(hw, I40E_PFINT_ICR0_ENA, 0);
>   	val = 0x3 << I40E_PFINT_DYN_CTLN_ITR_INDX_SHIFT;
> -	for (i = 0; i < num_pf_int - 2; i++)
> -		wr32(hw, I40E_PFINT_DYN_CTLN(i), val);
> +	if (num_pf_int > 1) {

instead of adding if conditions, I would simply change the type
to be signed

> +		for (i = 0; i < num_pf_int - 2; i++)
> +			wr32(hw, I40E_PFINT_DYN_CTLN(i), val);
> +	}
>   
>   	/* Set the FIRSTQ_INDX field to 0x7FF in PFINT_LNKLSTx */
>   	val = eol << I40E_PFINT_LNKLST0_FIRSTQ_INDX_SHIFT;
>   	wr32(hw, I40E_PFINT_LNKLST0, val);
> -	for (i = 0; i < num_pf_int - 2; i++)
> -		wr32(hw, I40E_PFINT_LNKLSTN(i), val);
> +	if (num_pf_int > 1) {
> +		for (i = 0; i < num_pf_int - 2; i++)
> +			wr32(hw, I40E_PFINT_LNKLSTN(i), val);
> +	}
>   	val = eol << I40E_VPINT_LNKLST0_FIRSTQ_INDX_SHIFT;
>   	for (i = 0; i < num_vfs; i++)
>   		wr32(hw, I40E_VPINT_LNKLST0(i), val);
> -	for (i = 0; i < num_vf_int - 2; i++)
> -		wr32(hw, I40E_VPINT_LNKLSTN(i), val);
> +	if (num_vf_int > 1) {
> +		for (i = 0; i < num_vf_int - 2; i++)
> +			wr32(hw, I40E_VPINT_LNKLSTN(i), val);
> +	}
>   
>   	/* warn the HW of the coming Tx disables */
>   	for (i = 0; i < num_queues; i++) {
> 
> 
> Could you check this?
> 
> Best regards,
> Kyungwook Boo