powerpc/audit: Fix syscall_get_arch()

Commit 770cec1 ("powerpc/audit: Simplify syscall_get_arch()")
and commit 898a1ef ("powerpc/audit: Avoid unneccessary #ifdef
in syscall_get_arguments()")
replaced test_tsk_thread_flag(task, TIF_32BIT)) by is_32bit_task().

But is_32bit_task() applies on current task while be want the test
done on task 'task'

So add a new macro is_tsk_32bit_task() to check any task.

Fixes: 770cec1 ("powerpc/audit: Simplify syscall_get_arch()")
Fixes: 898a1ef ("powerpc/audit: Avoid unneccessary #ifdef in syscall_get_arguments()")
Cc: stable@vger.kernel.org
Reported-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/c55cddb8f65713bf5859ed675d75a50cb37d5995.1642159570.git.christophe.leroy@csgroup.eu

Author: chleroy

arch/powerpc/include/asm/syscall.h

@@ -90,7 +90,7 @@ static inline void syscall_get_arguments(struct task_struct *task,
 	unsigned long val, mask = -1UL;
 	unsigned int n = 6;
 
-	if (is_32bit_task())
+	if (is_tsk_32bit_task(task))
 		mask = 0xffffffff;
 
 	while (n--) {
@@ -105,7 +105,7 @@ static inline void syscall_get_arguments(struct task_struct *task,
 
 static inline int syscall_get_arch(struct task_struct *task)
 {
-	if (is_32bit_task())
+	if (is_tsk_32bit_task(task))
 		return AUDIT_ARCH_PPC;
 	else if (IS_ENABLED(CONFIG_CPU_LITTLE_ENDIAN))
 		return AUDIT_ARCH_PPC64LE;

arch/powerpc/include/asm/thread_info.h

@@ -168,8 +168,10 @@ static inline bool test_thread_local_flags(unsigned int flags)
 
 #ifdef CONFIG_COMPAT
 #define is_32bit_task()	(test_thread_flag(TIF_32BIT))
+#define is_tsk_32bit_task(tsk)	(test_tsk_thread_flag(tsk, TIF_32BIT))
 #else
 #define is_32bit_task()	(IS_ENABLED(CONFIG_PPC32))
+#define is_tsk_32bit_task(tsk)	(IS_ENABLED(CONFIG_PPC32))
 #endif
 
 #if defined(CONFIG_PPC64)