4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
commit 6347e8d5bcce33fc36e651901efefbe2c93a43ef 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@xxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 19 +++++++++++++------
include/linux/mm.h | 2 +-
mm/memory.c | 11 +++--------
mm/nommu.c | 7 +++----
4 files changed, 20 insertions(+), 19 deletions(-)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -254,7 +254,7 @@ static ssize_t proc_pid_cmdline_read(str
* Inherently racy -- command line shares address space
* with code and data.
*/
- rv = access_remote_vm(mm, arg_end - 1, &c, 1, 0);
+ rv = access_remote_vm(mm, arg_end - 1, &c, 1, FOLL_FORCE);
if (rv <= 0)
goto out_free_page;
@@ -272,7 +272,8 @@ static ssize_t proc_pid_cmdline_read(str
int nr_read;
_count = min3(count, len, PAGE_SIZE);
- nr_read = access_remote_vm(mm, p, page, _count, 0);
+ nr_read = access_remote_vm(mm, p, page, _count,
+ FOLL_FORCE);
if (nr_read < 0)
rv = nr_read;
if (nr_read <= 0)
@@ -307,7 +308,8 @@ static ssize_t proc_pid_cmdline_read(str
bool final;
_count = min3(count, len, PAGE_SIZE);
- nr_read = access_remote_vm(mm, p, page, _count, 0);
+ nr_read = access_remote_vm(mm, p, page, _count,
+ FOLL_FORCE);
if (nr_read < 0)
rv = nr_read;
if (nr_read <= 0)
@@ -356,7 +358,8 @@ skip_argv:
bool final;
_count = min3(count, len, PAGE_SIZE);
- nr_read = access_remote_vm(mm, p, page, _count, 0);
+ nr_read = access_remote_vm(mm, p, page, _count,
+ FOLL_FORCE);
if (nr_read < 0)
rv = nr_read;
if (nr_read <= 0)
@@ -868,6 +871,7 @@ static ssize_t mem_rw(struct file *file,
unsigned long addr = *ppos;
ssize_t copied;
char *page;
+ unsigned int flags = FOLL_FORCE;
if (!mm)
return 0;
@@ -880,6 +884,9 @@ static ssize_t mem_rw(struct file *file,
if (!atomic_inc_not_zero(&mm->mm_users))
goto free;
+ if (write)
+ flags |= FOLL_WRITE;
+
while (count > 0) {
int this_len = min_t(int, count, PAGE_SIZE);
@@ -888,7 +895,7 @@ static ssize_t mem_rw(struct file *file,
break;
}
- this_len = access_remote_vm(mm, addr, page, this_len, write);
+ this_len = access_remote_vm(mm, addr, page, this_len, flags);
if (!this_len) {
if (!copied)
copied = -EIO;
@@ -1001,7 +1008,7 @@ static ssize_t environ_read(struct file
this_len = min(max_len, this_len);
retval = access_remote_vm(mm, (env_start + src),
- page, this_len, 0);
+ page, this_len, FOLL_FORCE);
if (retval <= 0) {
ret = retval;
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1191,7 +1191,7 @@ static inline int fixup_user_fault(struc
extern int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write);
extern int access_remote_vm(struct mm_struct *mm, unsigned long addr,
- void *buf, int len, int write);
+ void *buf, int len, unsigned int gup_flags);
long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3777,19 +3777,14 @@ static int __access_remote_vm(struct tas
* @addr: start address to access
* @buf: source or destination buffer
* @len: number of bytes to transfer
- * @write: whether the access is a write
+ * @gup_flags: flags modifying lookup behaviour
*
* The caller must hold a reference on @mm.
*/
int access_remote_vm(struct mm_struct *mm, unsigned long addr,
- void *buf, int len, int write)
+ void *buf, int len, unsigned int gup_flags)
{
- unsigned int flags = FOLL_FORCE;
-
- if (write)
- flags |= FOLL_WRITE;
-
- return __access_remote_vm(NULL, mm, addr, buf, len, flags);
+ return __access_remote_vm(NULL, mm, addr, buf, len, gup_flags);
}
/*
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1967,15 +1967,14 @@ static int __access_remote_vm(struct tas
* @addr: start address to access
* @buf: source or destination buffer
* @len: number of bytes to transfer
- * @write: whether the access is a write
+ * @gup_flags: flags modifying lookup behaviour
*
* The caller must hold a reference on @mm.
*/
int access_remote_vm(struct mm_struct *mm, unsigned long addr,
- void *buf, int len, int write)
+ void *buf, int len, unsigned int gup_flags)
{
- return __access_remote_vm(NULL, mm, addr, buf, len,
- write ? FOLL_WRITE : 0);
+ return __access_remote_vm(NULL, mm, addr, buf, len, gup_flags);
}
/*
