Re: [PATCH 10/10] mm: replace access_process_vm() write parameter with gup_flags

[Jesper Nilsson]

On Thu, Oct 13, 2016 at 01:20:20AM +0100, Lorenzo Stoakes wrote:
> This patch removes the write parameter from access_process_vm() and replaces 
> it
> with a gup_flags parameter as use of this function previously _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 
> ---
>  arch/cris/arch-v32/kernel/ptrace.c |  4 ++--

For the CRIS part:

Acked-by: Jesper Nilsson 

/^JN - Jesper Nilsson
-- 
   Jesper Nilsson -- jesper.nils...@axis.com

[PATCH 10/10] mm: replace access_process_vm() write parameter with gup_flags

[Lorenzo Stoakes]

This patch removes the write parameter from access_process_vm() and replaces it
with a gup_flags parameter as use of this function previously _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 
---
 arch/alpha/kernel/ptrace.c |  9 ++---
 arch/blackfin/kernel/ptrace.c  |  5 +++--
 arch/cris/arch-v32/kernel/ptrace.c |  4 ++--
 arch/ia64/kernel/ptrace.c  | 14 +-
 arch/m32r/kernel/ptrace.c  | 15 ++-
 arch/mips/kernel/ptrace32.c|  5 +++--
 arch/powerpc/kernel/ptrace32.c |  5 +++--
 arch/score/kernel/ptrace.c | 10 ++
 arch/sparc/kernel/ptrace_64.c  | 24 
 arch/x86/kernel/step.c |  3 ++-
 arch/x86/um/ptrace_32.c|  3 ++-
 arch/x86/um/ptrace_64.c|  3 ++-
 include/linux/mm.h |  3 ++-
 kernel/ptrace.c| 16 ++--
 mm/memory.c|  8 ++--
 mm/nommu.c |  6 +++---
 mm/util.c  |  5 +++--
 17 files changed, 84 insertions(+), 54 deletions(-)

diff --git a/arch/alpha/kernel/ptrace.c b/arch/alpha/kernel/ptrace.c
index d9ee817..940dfb4 100644
--- a/arch/alpha/kernel/ptrace.c
+++ b/arch/alpha/kernel/ptrace.c
@@ -157,14 +157,16 @@ put_reg(struct task_struct *task, unsigned long regno, 
unsigned long data)
 static inline int
 read_int(struct task_struct *task, unsigned long addr, int * data)
 {
-   int copied = access_process_vm(task, addr, data, sizeof(int), 0);
+   int copied = access_process_vm(task, addr, data, sizeof(int),
+   FOLL_FORCE);
return (copied == sizeof(int)) ? 0 : -EIO;
 }
 
 static inline int
 write_int(struct task_struct *task, unsigned long addr, int data)
 {
-   int copied = access_process_vm(task, addr, , sizeof(int), 1);
+   int copied = access_process_vm(task, addr, , sizeof(int),
+   FOLL_FORCE | FOLL_WRITE);
return (copied == sizeof(int)) ? 0 : -EIO;
 }
 
@@ -281,7 +283,8 @@ long arch_ptrace(struct task_struct *child, long request,
/* When I and D space are separate, these will need to be fixed.  */
case PTRACE_PEEKTEXT: /* read word at location addr. */
case PTRACE_PEEKDATA:
-   copied = access_process_vm(child, addr, , sizeof(tmp), 0);
+   copied = access_process_vm(child, addr, , sizeof(tmp),
+   FOLL_FORCE);
ret = -EIO;
if (copied != sizeof(tmp))
break;
diff --git a/arch/blackfin/kernel/ptrace.c b/arch/blackfin/kernel/ptrace.c
index 8b8fe67..8d79286 100644
--- a/arch/blackfin/kernel/ptrace.c
+++ b/arch/blackfin/kernel/ptrace.c
@@ -271,7 +271,7 @@ long arch_ptrace(struct task_struct *child, long request,
case BFIN_MEM_ACCESS_CORE:
case BFIN_MEM_ACCESS_CORE_ONLY:
copied = access_process_vm(child, addr, ,
-  to_copy, 0);
+  to_copy, FOLL_FORCE);
if (copied)
break;
 
@@ -324,7 +324,8 @@ long arch_ptrace(struct task_struct *child, long request,
case BFIN_MEM_ACCESS_CORE:
case BFIN_MEM_ACCESS_CORE_ONLY:
copied = access_process_vm(child, addr, ,
-  to_copy, 1);
+  to_copy,
+  FOLL_FORCE | 
FOLL_WRITE);
break;
case BFIN_MEM_ACCESS_DMA:
if (safe_dma_memcpy(paddr, , to_copy))
diff --git a/arch/cris/arch-v32/kernel/ptrace.c 
b/arch/cris/arch-v32/kernel/ptrace.c
index f085229..f0df654 100644
--- a/arch/cris/arch-v32/kernel/ptrace.c
+++ b/arch/cris/arch-v32/kernel/ptrace.c
@@ -147,7 +147,7 @@ long arch_ptrace(struct task_struct *child, long request,
/* The trampoline page is globally mapped, no 
page table to traverse.*/
tmp = *(unsigned long*)addr;
} else {
-   copied = access_process_vm(child, addr, , 
sizeof(tmp), 0);
+   copied = access_process_vm(child, addr, , 
sizeof(tmp), FOLL_FORCE);
 
if (copied != sizeof(tmp))
break;
@@ -279,7 +279,7 @@ static int insn_size(struct task_struct *child, unsigned 
long pc)
   int opsize = 0;
 
   /* Read the