X-Git-Url: https://git.kernel.dk/?a=blobdiff_plain;f=mm%2Fgup.c;h=ad28261dcafdcb4f373dd9b715047729eb7f5035;hb=c8070b78751955e59b42457b974bea4a4fe00187;hp=ff689c88a35781f1d9aeccd00458028a308cdb42;hpb=58390c8ce1bddb6c623f62e7ed36383e7fa5c02f;p=linux-block.git

diff --git a/mm/gup.c b/mm/gup.c
index ff689c88a357..ad28261dcafd 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -51,7 +51,8 @@ static inline void sanity_check_pinned_pages(struct page **pages,
 		struct page *page = *pages;
 		struct folio *folio = page_folio(page);
 
-		if (!folio_test_anon(folio))
+		if (is_zero_page(page) ||
+		    !folio_test_anon(folio))
 			continue;
 		if (!folio_test_large(folio) || folio_test_hugetlb(folio))
 			VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page), page);
@@ -131,6 +132,13 @@ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags)
 	else if (flags & FOLL_PIN) {
 		struct folio *folio;
 
+		/*
+		 * Don't take a pin on the zero page - it's not going anywhere
+		 * and it is used in a *lot* of places.
+		 */
+		if (is_zero_page(page))
+			return page_folio(page);
+
 		/*
 		 * Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a
 		 * right zone, so fail and let the caller fall back to the slow
@@ -180,6 +188,8 @@ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags)
 static void gup_put_folio(struct folio *folio, int refs, unsigned int flags)
 {
 	if (flags & FOLL_PIN) {
+		if (is_zero_folio(folio))
+			return;
 		node_stat_mod_folio(folio, NR_FOLL_PIN_RELEASED, refs);
 		if (folio_test_large(folio))
 			atomic_sub(refs, &folio->_pincount);
@@ -224,6 +234,13 @@ int __must_check try_grab_page(struct page *page, unsigned int flags)
 	if (flags & FOLL_GET)
 		folio_ref_inc(folio);
 	else if (flags & FOLL_PIN) {
+		/*
+		 * Don't take a pin on the zero page - it's not going anywhere
+		 * and it is used in a *lot* of places.
+		 */
+		if (is_zero_page(page))
+			return 0;
+
 		/*
 		 * Similar to try_grab_folio(): be sure to *also*
 		 * increment the normal page refcount field at least once,
@@ -2970,6 +2987,8 @@ static int internal_get_user_pages_fast(unsigned long start,
 	len = nr_pages << PAGE_SHIFT;
 	if (check_add_overflow(start, len, &end))
 		return 0;
+	if (end > TASK_SIZE_MAX)
+		return -EFAULT;
 	if (unlikely(!access_ok((void __user *)start, len)))
 		return -EFAULT;
 
@@ -3077,6 +3096,9 @@ EXPORT_SYMBOL_GPL(get_user_pages_fast);
  *
  * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
  * see Documentation/core-api/pin_user_pages.rst for further details.
+ *
+ * Note that if a zero_page is amongst the returned pages, it will not have
+ * pins in it and unpin_user_page() will not remove pins from it.
  */
 int pin_user_pages_fast(unsigned long start, int nr_pages,
 			unsigned int gup_flags, struct page **pages)
@@ -3108,6 +3130,9 @@ EXPORT_SYMBOL_GPL(pin_user_pages_fast);
  *
  * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
  * see Documentation/core-api/pin_user_pages.rst for details.
+ *
+ * Note that if a zero_page is amongst the returned pages, it will not have
+ * pins in it and unpin_user_page*() will not remove pins from it.
  */
 long pin_user_pages_remote(struct mm_struct *mm,
 			   unsigned long start, unsigned long nr_pages,
@@ -3141,6 +3166,9 @@ EXPORT_SYMBOL(pin_user_pages_remote);
  *
  * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
  * see Documentation/core-api/pin_user_pages.rst for details.
+ *
+ * Note that if a zero_page is amongst the returned pages, it will not have
+ * pins in it and unpin_user_page*() will not remove pins from it.
  */
 long pin_user_pages(unsigned long start, unsigned long nr_pages,
 		    unsigned int gup_flags, struct page **pages,
@@ -3159,6 +3187,9 @@ EXPORT_SYMBOL(pin_user_pages);
  * pin_user_pages_unlocked() is the FOLL_PIN variant of
  * get_user_pages_unlocked(). Behavior is the same, except that this one sets
  * FOLL_PIN and rejects FOLL_GET.
+ *
+ * Note that if a zero_page is amongst the returned pages, it will not have
+ * pins in it and unpin_user_page*() will not remove pins from it.
  */
 long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
 			     struct page **pages, unsigned int gup_flags)