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, 9 insertions, 5 deletions

diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c
index 6f54d511cc50..31aa8c0f68e1 100644
--- a/arch/ia64/kernel/ptrace.c
+++ b/arch/ia64/kernel/ptrace.c
@@ -453,7 +453,7 @@ ia64_peek (struct task_struct *child, struct switch_stack *child_stack,
                         return 0;
                 }
         }
-        copied = access_process_vm(child, addr, &ret, sizeof(ret), 0);
+        copied = access_process_vm(child, addr, &ret, sizeof(ret), FOLL_FORCE);
         if (copied != sizeof(ret))
                 return -EIO;
         *val = ret;
@@ -489,7 +489,8 @@ ia64_poke (struct task_struct *child, struct switch_stack *child_stack,
                                 *ia64_rse_skip_regs(krbs, regnum) = val;
                         }
                 }
-        } else if (access_process_vm(child, addr, &val, sizeof(val), 1)
+        } else if (access_process_vm(child, addr, &val, sizeof(val),
+                                FOLL_FORCE | FOLL_WRITE)
                    != sizeof(val))
                 return -EIO;
         return 0;
@@ -543,7 +544,8 @@ ia64_sync_user_rbs (struct task_struct *child, struct switch_stack *sw,
                 ret = ia64_peek(child, sw, user_rbs_end, addr, &val);
                 if (ret < 0)
                         return ret;
-                if (access_process_vm(child, addr, &val, sizeof(val), 1)
+                if (access_process_vm(child, addr, &val, sizeof(val),
+                                FOLL_FORCE | FOLL_WRITE)
                     != sizeof(val))
                         return -EIO;
         }
@@ -559,7 +561,8 @@ ia64_sync_kernel_rbs (struct task_struct *child, struct switch_stack *sw,
 
         /* now copy word for word from user rbs to kernel rbs: */
         for (addr = user_rbs_start; addr < user_rbs_end; addr += 8) {
-                if (access_process_vm(child, addr, &val, sizeof(val), 0)
+                if (access_process_vm(child, addr, &val, sizeof(val),
+                                FOLL_FORCE)
                                 != sizeof(val))
                         return -EIO;
 
@@ -1156,7 +1159,8 @@ arch_ptrace (struct task_struct *child, long request,
         case PTRACE_PEEKTEXT:
         case PTRACE_PEEKDATA:
                 /* read word at location addr */
-                if (access_process_vm(child, addr, &data, sizeof(data), 0)
+                if (access_process_vm(child, addr, &data, sizeof(data),
+                                FOLL_FORCE)
                     != sizeof(data))
                         return -EIO;
                 /* ensure return value is not mistaken for error code */