mm: replace access_process_vm() write parameter with gup_flags

This removes the 'write' argument from access_process_vm() and replaces
it with 'gup_flags' as use of this function previously silently implied
FOLL_FORCE, whereas after this patch callers explicitly pass this flag.

We make this explicit as use of FOLL_FORCE can result in surprising
behaviour (and hence bugs) within the mm subsystem.

Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/mm/util.c b/mm/util.c
index 4c685bde5ebc..952cbe7ad7b7 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -624,7 +624,7 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
         if (len > buflen)
                 len = buflen;
 
-        res = access_process_vm(task, arg_start, buffer, len, 0);
+        res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);
 
         /*
          * If the nul at the end of args has been overwritten, then
@@ -639,7 +639,8 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
                         if (len > buflen - res)
                                 len = buflen - res;
                         res += access_process_vm(task, env_start,
-                                                 buffer+res, len, 0);
+                                                 buffer+res, len,
+                                                 FOLL_FORCE);
                         res = strnlen(buffer, res);
                 }
         }