On Tue, May 16, 2023 at 11:49:19AM +0200, Anders Roxell wrote:
> On 2023-05-14 22:26, Lorenzo Stoakes wrote:
> > 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.
> >
> > We are able to perform these VMA operations as we already hold the
> > mmap_lock in order to be able to call get_user_pages_remote().
> >
> > As part of this work we add get_user_page_vma_remote() which abstracts the
> > VMA lookup, error handling and decrementing the page reference count should
> > the VMA lookup fail.
> >
> > This forms part of a broader set of patches intended to eliminate the vmas
> > parameter altogether.
> >
> > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> (for arm64)
> > Acked-by: David Hildenbrand <david@redhat.com>
> > Reviewed-by: Janosch Frank <frankja@linux.ibm.com> (for s390)
> > Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
> > ---
> > arch/arm64/kernel/mte.c | 17 +++++++++--------
> > arch/s390/kvm/interrupt.c | 2 +-
> > fs/exec.c | 2 +-
> > include/linux/mm.h | 34 +++++++++++++++++++++++++++++++---
> > kernel/events/uprobes.c | 13 +++++--------
> > mm/gup.c | 12 ++++--------
> > mm/memory.c | 14 +++++++-------
> > mm/rmap.c | 2 +-
> > security/tomoyo/domain.c | 2 +-
> > virt/kvm/async_pf.c | 3 +--
> > 10 files changed, 61 insertions(+), 40 deletions(-)
> >
>
> [...]
>
> > diff --git a/mm/memory.c b/mm/memory.c
> > index 146bb94764f8..63632a5eafc1 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -5590,7 +5590,6 @@ EXPORT_SYMBOL_GPL(generic_access_phys);
> > int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
> > int len, unsigned int gup_flags)
> > {
> > - struct vm_area_struct *vma;
> > void *old_buf = buf;
> > int write = gup_flags & FOLL_WRITE;
> >
> > @@ -5599,13 +5598,15 @@ int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
> >
> > /* ignore errors, just check how much was successfully transferred */
> > while (len) {
> > - int bytes, ret, offset;
> > + int bytes, offset;
> > void *maddr;
> > - struct page *page = NULL;
> > + struct vm_area_struct *vma;
> > + struct page *page = get_user_page_vma_remote(mm, addr,
> > + gup_flags, &vma);
> > +
> > + if (IS_ERR_OR_NULL(page)) {
> > + int ret = 0;
>
> I see the warning below when building without CONFIG_HAVE_IOREMAP_PROT set.
>
> make --silent --keep-going --jobs=32 \
> O=/home/anders/.cache/tuxmake/builds/1244/build ARCH=arm \
> CROSS_COMPILE=arm-linux-gnueabihf- /home/anders/src/kernel/next/mm/memory.c: In function '__access_remote_vm':
> /home/anders/src/kernel/next/mm/memory.c:5608:29: warning: unused variable 'ret' [-Wunused-variable]
> 5608 | int ret = 0;
> | ^~~
>
Ah damn, nice spot thanks!
>
> >
> > - ret = get_user_pages_remote(mm, addr, 1,
> > - gup_flags, &page, &vma, NULL);
> > - if (ret <= 0) {
> > #ifndef CONFIG_HAVE_IOREMAP_PROT
> > break;
> > #else
> > @@ -5613,7 +5614,6 @@ 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)
>
> Cheers,
> Anders
I enclose a -fix patch for this below:-
----8<----
From 6a4bb033a1ec60920e4945e7e063443f91489d06 Mon Sep 17 00:00:00 2001
From: Lorenzo Stoakes <lstoakes@gmail.com>
Date: Tue, 16 May 2023 19:16:22 +0100
Subject: [PATCH] mm/gup: remove vmas parameter from get_user_pages_remote()
Fix unused variable warning as reported by Anders Roxell.
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
---
mm/memory.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 63632a5eafc1..b1b25e61294a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5605,11 +5605,11 @@ int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
gup_flags, &vma);
if (IS_ERR_OR_NULL(page)) {
- int ret = 0;
-
#ifndef CONFIG_HAVE_IOREMAP_PROT
break;
#else
+ int ret = 0;
+
/*
* Check if this is a VM_IO | VM_PFNMAP VMA, which
* we can access using slightly different code.
--
2.40.1
@@ -419,10 +419,9 @@ 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;
+ int err = 0;
int write = gup_flags & FOLL_WRITE;
if (!access_ok(buf, len))
@@ -432,14 +431,16 @@ 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;
+ struct page *page = get_user_page_vma_remote(mm, addr,
+ gup_flags, &vma);
- ret = get_user_pages_remote(mm, addr, 1, gup_flags, &page,
- &vma, NULL);
- if (ret <= 0)
+ if (IS_ERR_OR_NULL(page)) {
+ err = page == NULL ? -EIO : PTR_ERR(page);
break;
+ }
/*
* Only copy tags if the page has been mapped as PROT_MTE
@@ -449,7 +450,7 @@ static int __access_remote_tags(struct mm_struct *mm, unsigned long addr,
* was never mapped with PROT_MTE.
*/
if (!(vma->vm_flags & VM_MTE)) {
- ret = -EOPNOTSUPP;
+ err = -EOPNOTSUPP;
put_page(page);
break;
}
@@ -482,7 +483,7 @@ static int __access_remote_tags(struct mm_struct *mm, unsigned long addr,
kiov->iov_len = buf - kiov->iov_base;
if (!kiov->iov_len) {
/* check for error accessing the tracee's address space */
- if (ret <= 0)
+ if (err)
return -EIO;
else
return -EFAULT;
@@ -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;
}
@@ -220,7 +220,7 @@ 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;
@@ -2366,6 +2366,9 @@ static inline void unmap_shared_mapping_range(struct address_space *mapping,
unmap_mapping_range(mapping, holebegin, holelen, 0);
}
+static inline struct vm_area_struct *vma_lookup(struct mm_struct *mm,
+ unsigned long addr);
+
extern int access_process_vm(struct task_struct *tsk, unsigned long addr,
void *buf, int len, unsigned int gup_flags);
extern int access_remote_vm(struct mm_struct *mm, unsigned long addr,
@@ -2374,13 +2377,38 @@ extern int __access_remote_vm(struct mm_struct *mm, unsigned long addr,
void *buf, int len, unsigned int gup_flags);
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);
+ unsigned long start, unsigned long nr_pages,
+ unsigned int gup_flags, struct page **pages,
+ 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,
int *locked);
+
+static inline struct page *get_user_page_vma_remote(struct mm_struct *mm,
+ unsigned long addr,
+ int gup_flags,
+ struct vm_area_struct **vmap)
+{
+ struct page *page;
+ struct vm_area_struct *vma;
+ int got = get_user_pages_remote(mm, addr, 1, gup_flags, &page, NULL);
+
+ if (got < 0)
+ return ERR_PTR(got);
+ if (got == 0)
+ return NULL;
+
+ vma = vma_lookup(mm, addr);
+ if (WARN_ON_ONCE(!vma)) {
+ put_page(page);
+ return ERR_PTR(-EINVAL);
+ }
+
+ *vmap = vma;
+ return page;
+}
+
long get_user_pages(unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages);
long pin_user_pages(unsigned long start, unsigned long nr_pages,
@@ -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,
@@ -474,10 +473,9 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
if (is_register)
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);
- if (ret <= 0)
- return ret;
+ old_page = get_user_page_vma_remote(mm, vaddr, gup_flags, &vma);
+ if (IS_ERR_OR_NULL(old_page))
+ return PTR_ERR(old_page);
ret = verify_opcode(old_page, vaddr, &opcode);
if (ret <= 0)
@@ -2027,8 +2025,7 @@ 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;
@@ -2208,8 +2208,6 @@ 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.
@@ -2224,8 +2222,6 @@ 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
@@ -2262,15 +2258,15 @@ 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);
}
@@ -2280,7 +2276,7 @@ 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;
}
@@ -5590,7 +5590,6 @@ EXPORT_SYMBOL_GPL(generic_access_phys);
int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
int len, unsigned int gup_flags)
{
- struct vm_area_struct *vma;
void *old_buf = buf;
int write = gup_flags & FOLL_WRITE;
@@ -5599,13 +5598,15 @@ int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
/* ignore errors, just check how much was successfully transferred */
while (len) {
- int bytes, ret, offset;
+ int bytes, offset;
void *maddr;
- struct page *page = NULL;
+ struct vm_area_struct *vma;
+ struct page *page = get_user_page_vma_remote(mm, addr,
+ gup_flags, &vma);
+
+ if (IS_ERR_OR_NULL(page)) {
+ int ret = 0;
- ret = get_user_pages_remote(mm, addr, 1,
- gup_flags, &page, &vma, NULL);
- if (ret <= 0) {
#ifndef CONFIG_HAVE_IOREMAP_PROT
break;
#else
@@ -5613,7 +5614,6 @@ 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)
@@ -2328,7 +2328,7 @@ 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;
@@ -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;
@@ -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);