[PATCH v2 3/7] mm/gup: remove vmas parameter from get_user_pages_remote()

From: Lorenzo Stoakes
Date: Sat Apr 15 2023 - 05:08:50 EST

The only instances of get_user_pages_remote() invocations which used the
vmas parameter were for a single page which can instead simply look up the
VMA directly. In particular:-

- __update_ref_ctr() looked up the VMA but did nothing with it so we simply
remove it.

- __access_remote_vm() was already using vma_lookup() when the original
lookup failed so by doing the lookup directly this also de-duplicates the
code.

This forms part of a broader set of patches intended to eliminate the vmas
parameter altogether.

Signed-off-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
---
arch/arm64/kernel/mte.c | 7 ++++---
arch/s390/kvm/interrupt.c | 2 +-
fs/exec.c | 2 +-
include/linux/mm.h | 2 +-
kernel/events/uprobes.c | 12 +++++++-----
mm/gup.c | 12 ++++--------
mm/memory.c | 9 +++++----
mm/rmap.c | 2 +-
security/tomoyo/domain.c | 2 +-
virt/kvm/async_pf.c | 3 +--
10 files changed, 26 insertions(+), 27 deletions(-)

diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index f5bcb0dc6267..d43a744d7919 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -419,7 +419,6 @@ long get_mte_ctrl(struct task_struct *task)
static int __access_remote_tags(struct mm_struct *mm, unsigned long addr,
struct iovec *kiov, unsigned int gup_flags)
{
- struct vm_area_struct *vma;
void __user *buf = kiov->iov_base;
size_t len = kiov->iov_len;
int ret;
@@ -432,12 +431,13 @@ static int __access_remote_tags(struct mm_struct *mm, unsigned long addr,
return -EIO;

while (len) {
+ struct vm_area_struct *vma;
unsigned long tags, offset;
void *maddr;
struct page *page = NULL;

ret = get_user_pages_remote(mm, addr, 1, gup_flags, &page,
- &vma, NULL);
+ NULL);
if (ret <= 0)
break;

@@ -448,7 +448,8 @@ static int __access_remote_tags(struct mm_struct *mm, unsigned long addr,
* would cause the existing tags to be cleared if the page
* was never mapped with PROT_MTE.
*/
- if (!(vma->vm_flags & VM_MTE)) {
+ vma = vma_lookup(mm, addr);
+ if (!vma || !(vma->vm_flags & VM_MTE)) {
ret = -EOPNOTSUPP;
put_page(page);
break;
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 9250fde1f97d..c19d0cb7d2f2 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -2777,7 +2777,7 @@ static struct page *get_map_page(struct kvm *kvm, u64 uaddr)

mmap_read_lock(kvm->mm);
get_user_pages_remote(kvm->mm, uaddr, 1, FOLL_WRITE,
- &page, NULL, NULL);
+ &page, NULL);
mmap_read_unlock(kvm->mm);
return page;
}
diff --git a/fs/exec.c b/fs/exec.c
index 87cf3a2f0e9a..d8d48ee15aac 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -219,7 +219,7 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
*/
mmap_read_lock(bprm->mm);
ret = get_user_pages_remote(bprm->mm, pos, 1, gup_flags,
- &page, NULL, NULL);
+ &page, NULL);
mmap_read_unlock(bprm->mm);
if (ret <= 0)
return NULL;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index ec9875c59f6d..1bfe73a2b6d3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2374,7 +2374,7 @@ extern int __access_remote_vm(struct mm_struct *mm, unsigned long addr,
long get_user_pages_remote(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
- struct vm_area_struct **vmas, int *locked);
+ int *locked);
long pin_user_pages_remote(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 59887c69d54c..b21993cd2dcc 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -365,7 +365,6 @@ __update_ref_ctr(struct mm_struct *mm, unsigned long vaddr, short d)
{
void *kaddr;
struct page *page;
- struct vm_area_struct *vma;
int ret;
short *ptr;

@@ -373,7 +372,7 @@ __update_ref_ctr(struct mm_struct *mm, unsigned long vaddr, short d)
return -EINVAL;

ret = get_user_pages_remote(mm, vaddr, 1,
- FOLL_WRITE, &page, &vma, NULL);
+ FOLL_WRITE, &page, NULL);
if (unlikely(ret <= 0)) {
/*
* We are asking for 1 page. If get_user_pages_remote() fails,
@@ -475,10 +474,14 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
gup_flags |= FOLL_SPLIT_PMD;
/* Read the page with vaddr into memory */
ret = get_user_pages_remote(mm, vaddr, 1, gup_flags,
- &old_page, &vma, NULL);
+ &old_page, NULL);
if (ret <= 0)
return ret;

+ vma = vma_lookup(mm, vaddr);
+ if (!vma)
+ goto put_old;
+
ret = verify_opcode(old_page, vaddr, &opcode);
if (ret <= 0)
goto put_old;
@@ -2027,8 +2030,7 @@ static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)
* but we treat this as a 'remote' access since it is
* essentially a kernel access to the memory.
*/
- result = get_user_pages_remote(mm, vaddr, 1, FOLL_FORCE, &page,
- NULL, NULL);
+ result = get_user_pages_remote(mm, vaddr, 1, FOLL_FORCE, &page, NULL);
if (result < 0)
return result;

diff --git a/mm/gup.c b/mm/gup.c
index 931c805bc32b..9440aa54c741 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2165,8 +2165,6 @@ static bool is_valid_gup_args(struct page **pages, struct vm_area_struct **vmas,
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long. Or NULL, if caller
* only intends to ensure the pages are faulted in.
- * @vmas: array of pointers to vmas corresponding to each page.
- * Or NULL if the caller does not require them.
* @locked: pointer to lock flag indicating whether lock is held and
* subsequently whether VM_FAULT_RETRY functionality can be
* utilised. Lock must initially be held.
@@ -2181,8 +2179,6 @@ static bool is_valid_gup_args(struct page **pages, struct vm_area_struct **vmas,
*
* The caller is responsible for releasing returned @pages, via put_page().
*
- * @vmas are valid only as long as mmap_lock is held.
- *
* Must be called with mmap_lock held for read or write.
*
* get_user_pages_remote walks a process's page tables and takes a reference
@@ -2219,15 +2215,15 @@ static bool is_valid_gup_args(struct page **pages, struct vm_area_struct **vmas,
long get_user_pages_remote(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
- struct vm_area_struct **vmas, int *locked)
+ int *locked)
{
int local_locked = 1;

- if (!is_valid_gup_args(pages, vmas, locked, &gup_flags,
+ if (!is_valid_gup_args(pages, NULL, locked, &gup_flags,
FOLL_TOUCH | FOLL_REMOTE))
return -EINVAL;

- return __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
+ return __get_user_pages_locked(mm, start, nr_pages, pages, NULL,
locked ? locked : &local_locked,
gup_flags);
}
@@ -2237,7 +2233,7 @@ EXPORT_SYMBOL(get_user_pages_remote);
long get_user_pages_remote(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
- struct vm_area_struct **vmas, int *locked)
+ int *locked)
{
return 0;
}
diff --git a/mm/memory.c b/mm/memory.c
index 8ddb10199e8d..913e693322f2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5591,7 +5591,9 @@ int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
struct page *page = NULL;

ret = get_user_pages_remote(mm, addr, 1,
- gup_flags, &page, &vma, NULL);
+ gup_flags, &page, NULL);
+ vma = vma_lookup(mm, addr);
+
if (ret <= 0) {
#ifndef CONFIG_HAVE_IOREMAP_PROT
break;
@@ -5600,7 +5602,6 @@ int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
* Check if this is a VM_IO | VM_PFNMAP VMA, which
* we can access using slightly different code.
*/
- vma = vma_lookup(mm, addr);
if (!vma)
break;
if (vma->vm_ops && vma->vm_ops->access)
@@ -5617,11 +5618,11 @@ int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
bytes = PAGE_SIZE-offset;

maddr = kmap(page);
- if (write) {
+ if (write && vma) {
copy_to_user_page(vma, page, addr,
maddr + offset, buf, bytes);
set_page_dirty_lock(page);
- } else {
+ } else if (vma) {
copy_from_user_page(vma, page, addr,
buf, maddr + offset, bytes);
}
diff --git a/mm/rmap.c b/mm/rmap.c
index ba901c416785..756ea8a9bb90 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -2324,7 +2324,7 @@ int make_device_exclusive_range(struct mm_struct *mm, unsigned long start,

npages = get_user_pages_remote(mm, start, npages,
FOLL_GET | FOLL_WRITE | FOLL_SPLIT_PMD,
- pages, NULL, NULL);
+ pages, NULL);
if (npages < 0)
return npages;

diff --git a/security/tomoyo/domain.c b/security/tomoyo/domain.c
index 31af29f669d2..ac20c0bdff9d 100644
--- a/security/tomoyo/domain.c
+++ b/security/tomoyo/domain.c
@@ -916,7 +916,7 @@ bool tomoyo_dump_page(struct linux_binprm *bprm, unsigned long pos,
*/
mmap_read_lock(bprm->mm);
ret = get_user_pages_remote(bprm->mm, pos, 1,
- FOLL_FORCE, &page, NULL, NULL);
+ FOLL_FORCE, &page, NULL);
mmap_read_unlock(bprm->mm);
if (ret <= 0)
return false;
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index 9bfe1d6f6529..e033c79d528e 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -61,8 +61,7 @@ static void async_pf_execute(struct work_struct *work)
* access remotely.
*/
mmap_read_lock(mm);
- get_user_pages_remote(mm, addr, 1, FOLL_WRITE, NULL, NULL,
- &locked);
+ get_user_pages_remote(mm, addr, 1, FOLL_WRITE, NULL, &locked);
if (locked)
mmap_read_unlock(mm);

--
2.40.0