[PATCH 09/10] bus: mhi: core: Use correctly sized arguments for bit field

From: Kees Cook <redacted>

The find.h APIs are designed to be used only on unsigned long arguments.
This can technically result in a over-read, but it is harmless in this
case. Regardless, fix it to avoid the warning seen under -Warray-bounds,
which we'd like to enable globally:

In file included from ./include/linux/bitmap.h:9,
                 from ./include/linux/cpumask.h:12,
                 from ./arch/x86/include/asm/cpumask.h:5,
                 from ./arch/x86/include/asm/msr.h:11,
                 from ./arch/x86/include/asm/processor.h:22,
                 from ./arch/x86/include/asm/cpufeature.h:5,
                 from ./arch/x86/include/asm/thread_info.h:53,
                 from ./include/linux/thread_info.h:60,
                 from ./arch/x86/include/asm/preempt.h:7,
                 from ./include/linux/preempt.h:78,
                 from ./include/linux/spinlock.h:55,
                 from ./include/linux/wait.h:9,
                 from ./include/linux/wait_bit.h:8,
                 from ./include/linux/fs.h:6,
                 from ./include/linux/debugfs.h:15,
                 from drivers/bus/mhi/core/init.c:7:
drivers/bus/mhi/core/init.c: In function 'to_mhi_pm_state_str':
./include/linux/find.h:187:37: warning: array subscript 'long unsigned int[0]' is partly outside array bounds of 'enum mhi_pm_state[1]' [-Warray-bounds]
  187 |                 unsigned long val = *addr & GENMASK(size - 1, 0);
      |                                     ^~~~~
drivers/bus/mhi/core/init.c:80:51: note: while referencing 'state'
   80 | const char *to_mhi_pm_state_str(enum mhi_pm_state state)
      |                                 ~~~~~~~~~~~~~~~~~~^~~~~

Signed-off-by: Kees Cook <redacted>
Reviewed-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://lore.kernel.org/r/20211215232446.2069794-1-keescook@chromium.org (local)
[mani: changed the variable name "bits" to "pm_state"]
Signed-off-by: Manivannan Sadhasivam <redacted>
---
 drivers/bus/mhi/core/init.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index f1ec34417592..046f407dc5d6 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c

@@ -79,7 +79,8 @@ static const char * const mhi_pm_state_str[] = {
 
 const char *to_mhi_pm_state_str(enum mhi_pm_state state)
 {
-	int index = find_last_bit((unsigned long *)&state, 32);
+	unsigned long pm_state = state;
+	int index = find_last_bit(&pm_state, 32);
 
 	if (index >= ARRAY_SIZE(mhi_pm_state_str))
 		return "Invalid State";

-- 
2.25.1