UPSTREAM: mm: remove duplicated vma->vm_flags check when expanding stack

expand_upwards() and expand_downwards() will return -EFAULT if VM_GROWSUP
or VM_GROWSDOWN is not correctly set in vma->vm_flags, however in
!CONFIG_STACK_GROWSUP case, expand_stack_locked() returns -EINVAL first if
!(vma->vm_flags & VM_GROWSDOWN) before calling expand_downwards(), to keep
the consistency with CONFIG_STACK_GROWSUP case, remove this check.

The usages of this function are as below:

A:fs/exec.c
ret = expand_stack_locked(vma, stack_base);
if (ret)
	ret = -EFAULT;

or

B:mm/memory.c mm/mmap.c
if (expand_stack_locked(vma, addr))
	return NULL;

which means the return value will not propagate to other places, so I
believe there is no user-visible effects of this change, and it's
unnecessary to backport to earlier versions.

Bug: 254441685
Link: https://lkml.kernel.org/r/20230906103312.645712-1-xiujianfeng@huaweicloud.com
Fixes: f440fa1ac9 ("mm: make find_extend_vma() fail if write lock not held")
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 7fa38d0ea00ffe2cd3c95c96c85221b8ae221875)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: Ibb98909a9f9f07b64e339a55cb583b357f9d964b

mm/mmap.c

@@ -2232,8 +2232,6 @@ struct vm_area_struct *find_extend_vma_locked(struct mm_struct *mm, unsigned lon
 #else
 int expand_stack_locked(struct vm_area_struct *vma, unsigned long address)
 {
-	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
-		return -EINVAL;
 	return expand_downwards(vma, address);
 }