On Tue, Jun 11, 2019 at 10:18 PM Khalid Aziz [off-list ref] wrote:

On 6/3/19 10:55 AM, Andrey Konovalov wrote:

quoted

This patch is a part of a series that extends arm64 kernel ABI to allow to
pass tagged user pointers (with the top byte set to something else other
than 0x00) as syscall arguments.

do_pages_move() is used in the implementation of the move_pages syscall.

Untag user pointers in this function.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrey Konovalov <redacted>
---
 mm/migrate.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/migrate.c b/mm/migrate.c
index f2ecc2855a12..3930bb6fa656 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c

@@ -1617,6 +1617,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
              if (get_user(node, nodes + i))
                      goto out_flush;
              addr = (unsigned long)p;
+             addr = untagged_addr(addr);

Why not just "addr = (unsigned long)untagged_addr(p);"

Will do in the next version. I think I'll also merge this commit into
the "untag user pointers passed to memory syscalls" one.

--
Khalid

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