RE: [PATCH] firmware: xilinx: fix out-of-bounds access

[Rajan Vaja]

Hi Michal,


> -----Original Message-----
> From: Michal Simek <michal.simek@xxxxxxxxxx>
> Sent: 27 October 2020 05:27
> To: Rajan Vaja <RAJANV@xxxxxxxxxx>; Arnd Bergmann <arnd@xxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>; Greg Kroah-Hartman
> <gregkh@xxxxxxxxxxxxxxxxxxx>; Tejas Patel <TEJASP@xxxxxxxxxx>; linux-arm-
> kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; git <git@xxxxxxxxxx>
> Subject: Re: [PATCH] firmware: xilinx: fix out-of-bounds access
> 
> 
> 
> On 27. 10. 20 13:23, Rajan Vaja wrote:
> > Hi Michal,
> >
> >> -----Original Message-----
> >> From: Michal Simek <michal.simek@xxxxxxxxxx>
> >> Sent: 27 October 2020 02:53
> >> To: Arnd Bergmann <arnd@xxxxxxxxxx>; Michal Simek <michals@xxxxxxxxxx>;
> >> Rajan Vaja <RAJANV@xxxxxxxxxx>
> >> Cc: Arnd Bergmann <arnd@xxxxxxxx>; Rajan Vaja <RAJANV@xxxxxxxxxx>;
> Greg
> >> Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; Tejas Patel
> >> <TEJASP@xxxxxxxxxx>; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> >> kernel@xxxxxxxxxxxxxxx; git <git@xxxxxxxxxx>
> >> Subject: Re: [PATCH] firmware: xilinx: fix out-of-bounds access
> >>
> >>
> >>
> >> On 26. 10. 20 16:54, Arnd Bergmann wrote:
> >>> From: Arnd Bergmann <arnd@xxxxxxxx>
> >>>
> >>> The zynqmp_pm_set_suspend_mode() and
> >> zynqmp_pm_get_trustzone_version()
> >>> functions pass values as api_id into zynqmp_pm_invoke_fn
> >>> that are beyond PM_API_MAX, resulting in an out-of-bounds access:
> >>>
> >>> drivers/firmware/xilinx/zynqmp.c: In function
> >> 'zynqmp_pm_set_suspend_mode':
> >>> drivers/firmware/xilinx/zynqmp.c:150:24: warning: array subscript 2562 is
> above
> >> array bounds of 'u32[64]' {aka 'unsigned int[64]'} [-Warray-bounds]
> >>>   150 |  if (zynqmp_pm_features[api_id] != PM_FEATURE_UNCHECKED)
> >>>       |      ~~~~~~~~~~~~~~~~~~^~~~~~~~
> >>> drivers/firmware/xilinx/zynqmp.c:28:12: note: while referencing
> >> 'zynqmp_pm_features'
> >>>    28 | static u32 zynqmp_pm_features[PM_API_MAX];
> >>>       |            ^~~~~~~~~~~~~~~~~~
> >>
> >> Which CONFIG option/tool is reporting this issue?
> >>
> >>>
> >>> Replace the resulting undefined behavior with an error return.
> >>> This may break some things that happen to work at the moment
> >>> but seems better than randomly overwriting kernel data.
> >>>
> >>> I assume we need additional fixes for the two functions that now
> >>> return an error.
> >>>
> >>> Fixes: 76582671eb5d ("firmware: xilinx: Add Zynqmp firmware driver")
> >>> Fixes: e178df31cf41 ("firmware: xilinx: Implement ZynqMP power
> management
> >> APIs")
> >>> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> >>> ---
> >>>  drivers/firmware/xilinx/zynqmp.c | 3 +++
> >>>  1 file changed, 3 insertions(+)
> >>>
> >>> diff --git a/drivers/firmware/xilinx/zynqmp.c
> >> b/drivers/firmware/xilinx/zynqmp.c
> >>> index 8d1ff2454e2e..efb8a66efc68 100644
> >>> --- a/drivers/firmware/xilinx/zynqmp.c
> >>> +++ b/drivers/firmware/xilinx/zynqmp.c
> >>> @@ -147,6 +147,9 @@ static int zynqmp_pm_feature(u32 api_id)
> >>>  		return 0;
> >>>
> >>>  	/* Return value if feature is already checked */
> >>> +	if (api_id > ARRAY_SIZE(zynqmp_pm_features))
> >>> +		return PM_FEATURE_INVALID;
> >>> +
> >>>  	if (zynqmp_pm_features[api_id] != PM_FEATURE_UNCHECKED)
> >>>  		return zynqmp_pm_features[api_id];
> >>>
> >>>
> >>
> >> Definitely good catch but not quite sure what should be correct reaction.
> >> Rajan: Can you please take a look at it with priority?
> > [Rajan] Change looks fine to me.
> 
> as is mentioned above that two functions now returns and error
> PM_FEATURE_INVALID. Which means that zynqmp_pm_set_suspend_mode()
> and
> zynqmp_pm_get_trustzone_version() fail all the time which doesn't look
> correct.
[Rajan] Right Michal, I completely missed API which are not in pmufw ,  API IDs from ATF are different and it doesn't fit in PM_API_MAX range, so I think instead of just single array with PM_API_MAX size, implementation can be updated having, hash table kind of implementation and not directly in array index which is same as API ID.

Thanks,
Rajan 
> 
> M