get_user_pages_remote() will never return 0 except in the case of
FOLL_NOWAIT being specified, which we explicitly disallow.
This simplifies error handling for the caller and avoids the awkwardness of
dealing with both errors and failing to pin. Failing to pin here is an
error.
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
---
arch/arm64/kernel/mte.c | 4 ++--
include/linux/mm.h | 12 +++++++++---
kernel/events/uprobes.c | 4 ++--
mm/memory.c | 3 +--
4 files changed, 14 insertions(+), 9 deletions(-)
@@ -411,8 +411,8 @@ static int __access_remote_tags(struct mm_struct *mm, unsigned long addr,
struct page *page = get_user_page_vma_remote(mm, addr,
gup_flags, &vma);
- if (IS_ERR_OR_NULL(page)) {
- err = page == NULL ? -EIO : PTR_ERR(page);
+ if (IS_ERR(page)) {
+ err = PTR_ERR(page);
break;
}
@@ -2425,6 +2425,9 @@ long pin_user_pages_remote(struct mm_struct *mm,
unsigned int gup_flags, struct page **pages,
int *locked);
+/*
+ * Retrieves a single page alongside its VMA. Does not support FOLL_NOWAIT.
+ */
static inline struct page *get_user_page_vma_remote(struct mm_struct *mm,
unsigned long addr,
int gup_flags,
@@ -2432,12 +2435,15 @@ static inline struct page *get_user_page_vma_remote(struct mm_struct *mm,
{
struct page *page;
struct vm_area_struct *vma;
- int got = get_user_pages_remote(mm, addr, 1, gup_flags, &page, NULL);
+ int got;
+
+ if (WARN_ON_ONCE(unlikely(gup_flags & FOLL_NOWAIT)))
+ return ERR_PTR(-EINVAL);
+
+ 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)) {
@@ -474,8 +474,8 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
gup_flags |= FOLL_SPLIT_PMD;
/* Read the page with vaddr into memory */
old_page = get_user_page_vma_remote(mm, vaddr, gup_flags, &vma);
- if (IS_ERR_OR_NULL(old_page))
- return old_page ? PTR_ERR(old_page) : 0;
+ if (IS_ERR(old_page))
+ return PTR_ERR(old_page);
ret = verify_opcode(old_page, vaddr, &opcode);
if (ret <= 0)
@@ -5905,7 +5905,7 @@ static int __access_remote_vm(struct mm_struct *mm, unsigned long addr,
struct page *page = get_user_page_vma_remote(mm, addr,
gup_flags, &vma);
- if (IS_ERR_OR_NULL(page)) {
+ if (IS_ERR(page)) {
/* We might need to expand the stack to access it */
vma = vma_lookup(mm, addr);
if (!vma) {
@@ -5919,7 +5919,6 @@ static int __access_remote_vm(struct mm_struct *mm, unsigned long addr,
continue;
}
-
/*
* Check if this is a VM_IO | VM_PFNMAP VMA, which
* we can access using slightly different code.