ARM: mm: Kill task_struct argument for __do_page_fault()

hulk inclusion
category: bugfix
bugzilla: 167379
CVE: NA

Reference: https://lore.kernel.org/linux-arm-kernel/20210610123556.171328-1-wangkefeng.wang@huawei.com/

-------------------------------------------------

The __do_page_fault() won't use task_struct argument, kill it
and also use current->mm directly in do_page_fault().

No functional change.
Reviewed-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/arm/mm/fault.c

@@ -215,8 +215,7 @@ static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
 
 static vm_fault_t __kprobes
 __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
-		unsigned int flags, struct task_struct *tsk,
-		struct pt_regs *regs)
+		unsigned int flags, struct pt_regs *regs)
 {
 	struct vm_area_struct *vma = find_vma(mm, addr);
 	if (unlikely(!vma))
@@ -244,8 +243,7 @@ __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 static int __kprobes
 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 {
-	struct task_struct *tsk;
-	struct mm_struct *mm;
+	struct mm_struct *mm = current->mm;
 	int sig, code;
 	vm_fault_t fault;
 	unsigned int flags = FAULT_FLAG_DEFAULT;
@@ -253,8 +251,6 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 	if (kprobe_page_fault(regs, fsr))
 		return 0;
 
-	tsk = current;
-	mm  = tsk->mm;
 
 	/* Enable interrupts if they were enabled in the parent context. */
 	if (interrupts_enabled(regs))
@@ -298,7 +294,7 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 #endif
 	}
 
-	fault = __do_page_fault(mm, addr, fsr, flags, tsk, regs);
+	fault = __do_page_fault(mm, addr, fsr, flags, regs);
 
 	/* If we need to retry but a fatal signal is pending, handle the
 	 * signal first. We do not need to release the mmap_lock because