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, 10 insertions, 5 deletions

diff --git a/arch/m32r/kernel/ptrace.c b/arch/m32r/kernel/ptrace.c
index 51f5e9aa4901..c145605a981f 100644
--- a/arch/m32r/kernel/ptrace.c
+++ b/arch/m32r/kernel/ptrace.c
@@ -493,7 +493,8 @@ unregister_all_debug_traps(struct task_struct *child)
         int i;
 
         for (i = 0; i < p->nr_trap; i++)
-                access_process_vm(child, p->addr[i], &p->insn[i], sizeof(p->insn[i]), 1);
+                access_process_vm(child, p->addr[i], &p->insn[i], sizeof(p->insn[i]),
+                                FOLL_FORCE | FOLL_WRITE);
         p->nr_trap = 0;
 }
 
@@ -537,7 +538,8 @@ embed_debug_trap(struct task_struct *child, unsigned long next_pc)
         unsigned long next_insn, code;
         unsigned long addr = next_pc & ~3;
 
-        if (access_process_vm(child, addr, &next_insn, sizeof(next_insn), 0)
+        if (access_process_vm(child, addr, &next_insn, sizeof(next_insn),
+                        FOLL_FORCE)
             != sizeof(next_insn)) {
                 return -1; /* error */
         }
@@ -546,7 +548,8 @@ embed_debug_trap(struct task_struct *child, unsigned long next_pc)
         if (register_debug_trap(child, next_pc, next_insn, &code)) {
                 return -1; /* error */
         }
-        if (access_process_vm(child, addr, &code, sizeof(code), 1)
+        if (access_process_vm(child, addr, &code, sizeof(code),
+                        FOLL_FORCE | FOLL_WRITE)
             != sizeof(code)) {
                 return -1; /* error */
         }
@@ -562,7 +565,8 @@ withdraw_debug_trap(struct pt_regs *regs)
         addr = (regs->bpc - 2) & ~3;
         regs->bpc -= 2;
         if (unregister_debug_trap(current, addr, &code)) {
-            access_process_vm(current, addr, &code, sizeof(code), 1);
+            access_process_vm(current, addr, &code, sizeof(code),
+                    FOLL_FORCE | FOLL_WRITE);
             invalidate_cache();
         }
 }
@@ -589,7 +593,8 @@ void user_enable_single_step(struct task_struct *child)
         /* Compute next pc.  */
         pc = get_stack_long(child, PT_BPC);
 
-        if (access_process_vm(child, pc&~3, &insn, sizeof(insn), 0)
+        if (access_process_vm(child, pc&~3, &insn, sizeof(insn),
+                        FOLL_FORCE)
             != sizeof(insn))
                 return;