[RESEND PATCHv1] proc: use untagged_addr() for pagemap_read addresses

[Miles Chen]

When we try to visit the pagemap of a tagged userspace pointer, we find
that the start_vaddr is not correct because of the tag.
To fix it, we should untag the usespace pointers in pagemap_read().

Signed-off-by: Miles Chen <miles.chen at mediatek.com>
---
 fs/proc/task_mmu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 5066b0251ed8..ee0ac09e79fc 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1541,11 +1541,11 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
 
 	src = *ppos;
 	svpfn = src / PM_ENTRY_BYTES;
-	start_vaddr = svpfn << PAGE_SHIFT;
+	start_vaddr = untagged_addr(svpfn << PAGE_SHIFT);
 	end_vaddr = mm->task_size;
 
 	/* watch out for wraparound */
-	if (svpfn > mm->task_size >> PAGE_SHIFT)
+	if (start_vaddr > mm->task_size)
 		start_vaddr = end_vaddr;
 
 	/*
-- 
2.18.0