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mm: replace __access_remote_vm() write parameter with gup_flags

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commit 442486ec10 upstream.

This removes the 'write' argument from __access_remote_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: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 4.4: adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Lorenzo Stoakes 2016-10-13 01:20:18 +01:00 committed by Greg Kroah-Hartman
parent 8e50b8b07f
commit 2b8143d687
2 changed files with 21 additions and 11 deletions
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23
mm/memory.c
View File

@ -3711,14 +3711,11 @@ EXPORT_SYMBOL_GPL(generic_access_phys);
* given task for page fault accounting.
*/
static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
unsigned long addr, void *buf, int len, int write)
unsigned long addr, void *buf, int len, unsigned int gup_flags)
{
struct vm_area_struct *vma;
void *old_buf = buf;
unsigned int flags = FOLL_FORCE;
if (write)
flags |= FOLL_WRITE;
int write = gup_flags & FOLL_WRITE;
down_read(&mm->mmap_sem);
/* ignore errors, just check how much was successfully transferred */
@ -3728,7 +3725,7 @@ static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
struct page *page = NULL;
ret = get_user_pages(tsk, mm, addr, 1,
flags, &page, &vma);
gup_flags, &page, &vma);
if (ret <= 0) {
#ifndef CONFIG_HAVE_IOREMAP_PROT
break;
@ -3787,7 +3784,12 @@ static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
int access_remote_vm(struct mm_struct *mm, unsigned long addr,
void *buf, int len, int write)
{
return __access_remote_vm(NULL, mm, addr, buf, len, write);
unsigned int flags = FOLL_FORCE;
if (write)
flags |= FOLL_WRITE;
return __access_remote_vm(NULL, mm, addr, buf, len, flags);
}
/*
@ -3800,12 +3802,17 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr,
{
struct mm_struct *mm;
int ret;
unsigned int flags = FOLL_FORCE;
mm = get_task_mm(tsk);
if (!mm)
return 0;
ret = __access_remote_vm(tsk, mm, addr, buf, len, write);
if (write)
flags |= FOLL_WRITE;
ret = __access_remote_vm(tsk, mm, addr, buf, len, flags);
mmput(mm);
return ret;

9
mm/nommu.c
View File

@ -1929,9 +1929,10 @@ void filemap_map_pages(struct vm_area_struct *vma, struct vm_fault *vmf)
EXPORT_SYMBOL(filemap_map_pages);
static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
unsigned long addr, void *buf, int len, int write)
unsigned long addr, void *buf, int len, unsigned int gup_flags)
{
struct vm_area_struct *vma;
int write = gup_flags & FOLL_WRITE;
down_read(&mm->mmap_sem);
@ -1973,7 +1974,8 @@ static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
int access_remote_vm(struct mm_struct *mm, unsigned long addr,
void *buf, int len, int write)
{
return __access_remote_vm(NULL, mm, addr, buf, len, write);
return __access_remote_vm(NULL, mm, addr, buf, len,
write ? FOLL_WRITE : 0);
}
/*
@ -1991,7 +1993,8 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, in
if (!mm)
return 0;
len = __access_remote_vm(tsk, mm, addr, buf, len, write);
len = __access_remote_vm(tsk, mm, addr, buf, len,
write ? FOLL_WRITE : 0);
mmput(mm);
return len;