Merge tag 'mm-hotfixes-stable-2026-05-25-16-22' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mmHEADmaster

Pull misc fixes from Andrew Morton:
 "13 hotfixes. 9 are for MM. 9 are cc:stable and the remaining 4 address
  post-7.1 issues or aren't considered suitable for backporting.

  All patches are singletons - please see the individual changelogs for
  details"

* tag 'mm-hotfixes-stable-2026-05-25-16-22' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
  Revert "mm: introduce a new page type for page pool in page type"
  mm/vmalloc: do not trigger BUG() on BH disabled context
  MAINTAINERS, mailmap: change email for Eugen Hristev
  mm/migrate_device: fix pgtable leak in migrate_vma_insert_huge_pmd_page
  kernel/fork: validate exit_signal in kernel_clone()
  mm: memcontrol: propagate NMI slab stats to memcg vmstats
  mm/damon/sysfs-schemes: delete tried region in regions_rmdirs()
  mm/rmap: initialize nr_pages to 1 at loop start in try_to_unmap_one
  zram: fix use-after-free in zram_writeback_endio
  memfd: deny writeable mappings when implying SEAL_WRITE
  ipc: limit next_id allocation to the valid ID range
  Revert "mm/hugetlbfs: update hugetlbfs to use mmap_prepare"
  MAINTAINERS: .mailmap: update after GEHC spin-off

1 files changed, 24 insertions, 3 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index af23453e9dbd..06bbe9eba636 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -5174,9 +5174,10 @@ int arch_lock_shadow_stack_status(struct task_struct *t, unsigned long status);
  * DMA mapping IDs for page_pool
  *
  * When DMA-mapping a page, page_pool allocates an ID (from an xarray) and
- * stashes it in the upper bits of page->pp_magic. Non-PP pages can have
- * arbitrary kernel pointers stored in the same field as pp_magic (since
- * it overlaps with page->lru.next), so we must ensure that we cannot
+ * stashes it in the upper bits of page->pp_magic. We always want to be able to
+ * unambiguously identify page pool pages (using page_pool_page_is_pp()). Non-PP
+ * pages can have arbitrary kernel pointers stored in the same field as pp_magic
+ * (since it overlaps with page->lru.next), so we must ensure that we cannot
  * mistake a valid kernel pointer with any of the values we write into this
  * field.
  *
@@ -5211,6 +5212,26 @@ int arch_lock_shadow_stack_status(struct task_struct *t, unsigned long status);
 #define PP_DMA_INDEX_MASK GENMASK(PP_DMA_INDEX_BITS + PP_DMA_INDEX_SHIFT - 1, \
 				  PP_DMA_INDEX_SHIFT)
 
+/* Mask used for checking in page_pool_page_is_pp() below. page->pp_magic is
+ * OR'ed with PP_SIGNATURE after the allocation in order to preserve bit 0 for
+ * the head page of compound page and bit 1 for pfmemalloc page, as well as the
+ * bits used for the DMA index. page_is_pfmemalloc() is checked in
+ * __page_pool_put_page() to avoid recycling the pfmemalloc page.
+ */
+#define PP_MAGIC_MASK ~(PP_DMA_INDEX_MASK | 0x3UL)
+
+#ifdef CONFIG_PAGE_POOL
+static inline bool page_pool_page_is_pp(const struct page *page)
+{
+	return (page->pp_magic & PP_MAGIC_MASK) == PP_SIGNATURE;
+}
+#else
+static inline bool page_pool_page_is_pp(const struct page *page)
+{
+	return false;
+}
+#endif
+
 #define PAGE_SNAPSHOT_FAITHFUL (1 << 0)
 #define PAGE_SNAPSHOT_PG_BUDDY (1 << 1)
 #define PAGE_SNAPSHOT_PG_IDLE  (1 << 2)