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

[Arnd Bergmann]

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];
      |            ^~~~~~~~~~~~~~~~~~

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];
 
-- 
2.27.0