Merge tag 'mm-hotfixes-stable-2025-08-12-20-50' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull misc fixes from Andrew Morton:
 "12 hotfixes. 5 are cc:stable and the remainder address post-6.16
  issues or aren't considered necessary for -stable kernels.

  10 of these fixes are for MM"

* tag 'mm-hotfixes-stable-2025-08-12-20-50' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
  proc: proc_maps_open allow proc_mem_open to return NULL
  mm/mremap: avoid expensive folio lookup on mremap folio pte batch
  userfaultfd: fix a crash in UFFDIO_MOVE when PMD is a migration entry
  mm: pass page directly instead of using folio_page
  selftests/proc: fix string literal warning in proc-maps-race.c
  fs/proc/task_mmu: hold PTL in pagemap_hugetlb_range and gather_hugetlb_stats
  mm/smaps: fix race between smaps_hugetlb_range and migration
  mm: fix the race between collapse and PT_RECLAIM under per-vma lock
  mm/kmemleak: avoid soft lockup in __kmemleak_do_cleanup()
  MAINTAINERS: add Masami as a reviewer of hung task detector
  mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock
  kasan/test: fix protection against compiler elision

Author: torvalds

MAINTAINERS

@@ -11438,6 +11438,7 @@ F:	drivers/tty/hvc/
 HUNG TASK DETECTOR
 M:	Andrew Morton <[email protected]>
 R:	Lance Yang <[email protected]>
+R:	Masami Hiramatsu <[email protected]>
 L:	[email protected]
 S:	Maintained
 F:	include/linux/hung_task.h

fs/proc/task_mmu.c

@@ -340,8 +340,8 @@ static int proc_maps_open(struct inode *inode, struct file *file,
 
 	priv->inode = inode;
 	priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
-	if (IS_ERR_OR_NULL(priv->mm)) {
-		int err = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
+	if (IS_ERR(priv->mm)) {
+		int err = PTR_ERR(priv->mm);
 
 		seq_release_private(inode, file);
 		return err;
@@ -1148,10 +1148,13 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
 {
 	struct mem_size_stats *mss = walk->private;
 	struct vm_area_struct *vma = walk->vma;
-	pte_t ptent = huge_ptep_get(walk->mm, addr, pte);
 	struct folio *folio = NULL;
 	bool present = false;
+	spinlock_t *ptl;
+	pte_t ptent;
 
+	ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
+	ptent = huge_ptep_get(walk->mm, addr, pte);
 	if (pte_present(ptent)) {
 		folio = page_folio(pte_page(ptent));
 		present = true;
@@ -1170,6 +1173,7 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
 		else
 			mss->private_hugetlb += huge_page_size(hstate_vma(vma));
 	}
+	spin_unlock(ptl);
 	return 0;
 }
 #else
@@ -2017,12 +2021,14 @@ static int pagemap_hugetlb_range(pte_t *ptep, unsigned long hmask,
 	struct pagemapread *pm = walk->private;
 	struct vm_area_struct *vma = walk->vma;
 	u64 flags = 0, frame = 0;
+	spinlock_t *ptl;
 	int err = 0;
 	pte_t pte;
 
 	if (vma->vm_flags & VM_SOFTDIRTY)
 		flags |= PM_SOFT_DIRTY;
 
+	ptl = huge_pte_lock(hstate_vma(vma), walk->mm, ptep);
 	pte = huge_ptep_get(walk->mm, addr, ptep);
 	if (pte_present(pte)) {
 		struct folio *folio = page_folio(pte_page(pte));
@@ -2050,11 +2056,12 @@ static int pagemap_hugetlb_range(pte_t *ptep, unsigned long hmask,
 
 		err = add_to_pagemap(&pme, pm);
 		if (err)
-			return err;
+			break;
 		if (pm->show_pfn && (flags & PM_PRESENT))
 			frame++;
 	}
 
+	spin_unlock(ptl);
 	cond_resched();
 
 	return err;
@@ -3128,17 +3135,22 @@ static int gather_pte_stats(pmd_t *pmd, unsigned long addr,
 static int gather_hugetlb_stats(pte_t *pte, unsigned long hmask,
 		unsigned long addr, unsigned long end, struct mm_walk *walk)
 {
-	pte_t huge_pte = huge_ptep_get(walk->mm, addr, pte);
+	pte_t huge_pte;
 	struct numa_maps *md;
 	struct page *page;
+	spinlock_t *ptl;
 
+	ptl = huge_pte_lock(hstate_vma(walk->vma), walk->mm, pte);
+	huge_pte = huge_ptep_get(walk->mm, addr, pte);
 	if (!pte_present(huge_pte))
-		return 0;
+		goto out;
 
 	page = pte_page(huge_pte);
 
 	md = walk->private;
 	gather_stats(page, md, pte_dirty(huge_pte), 1);
+out:
+	spin_unlock(ptl);
 	return 0;
 }
 

mm/kasan/kasan_test_c.c

@@ -47,7 +47,7 @@ static struct {
  * Some tests use these global variables to store return values from function
  * calls that could otherwise be eliminated by the compiler as dead code.
  */
-static volatile void *kasan_ptr_result;
+static void *volatile kasan_ptr_result;
 static volatile int kasan_int_result;
 
 /* Probe for console output: obtains test_status lines of interest. */

mm/khugepaged.c

@@ -1172,11 +1172,11 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
 	if (result != SCAN_SUCCEED)
 		goto out_up_write;
 	/* check if the pmd is still valid */
+	vma_start_write(vma);
 	result = check_pmd_still_valid(mm, address, pmd);
 	if (result != SCAN_SUCCEED)
 		goto out_up_write;
 
-	vma_start_write(vma);
 	anon_vma_lock_write(vma->anon_vma);
 
 	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, address,

mm/kmemleak.c

@@ -470,6 +470,7 @@ static struct kmemleak_object *mem_pool_alloc(gfp_t gfp)
 {
 	unsigned long flags;
 	struct kmemleak_object *object;
+	bool warn = false;
 
 	/* try the slab allocator first */
 	if (object_cache) {
@@ -488,8 +489,10 @@ static struct kmemleak_object *mem_pool_alloc(gfp_t gfp)
 	else if (mem_pool_free_count)
 		object = &mem_pool[--mem_pool_free_count];
 	else
-		pr_warn_once("Memory pool empty, consider increasing CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE\n");
+		warn = true;
 	raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
+	if (warn)
+		pr_warn_once("Memory pool empty, consider increasing CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE\n");
 
 	return object;
 }
@@ -2181,6 +2184,7 @@ static const struct file_operations kmemleak_fops = {
 static void __kmemleak_do_cleanup(void)
 {
 	struct kmemleak_object *object, *tmp;
+	unsigned int cnt = 0;
 
 	/*
 	 * Kmemleak has already been disabled, no need for RCU list traversal
@@ -2189,6 +2193,10 @@ static void __kmemleak_do_cleanup(void)
 	list_for_each_entry_safe(object, tmp, &object_list, object_list) {
 		__remove_object(object);
 		__delete_object(object);
+
+		/* Call cond_resched() once per 64 iterations to avoid soft lockup */
+		if (!(++cnt & 0x3f))
+			cond_resched();
 	}
 }
 

mm/mprotect.c

@@ -120,9 +120,8 @@ static int mprotect_folio_pte_batch(struct folio *folio, pte_t *ptep,
 
 static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long addr,
 			   pte_t oldpte, pte_t *pte, int target_node,
-			   struct folio **foliop)
+			   struct folio *folio)
 {
-	struct folio *folio = NULL;
 	bool ret = true;
 	bool toptier;
 	int nid;
@@ -131,7 +130,6 @@ static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long addr,
 	if (pte_protnone(oldpte))
 		goto skip;
 
-	folio = vm_normal_folio(vma, addr, oldpte);
 	if (!folio)
 		goto skip;
 
@@ -173,7 +171,6 @@ static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long addr,
 		folio_xchg_access_time(folio, jiffies_to_msecs(jiffies));
 
 skip:
-	*foliop = folio;
 	return ret;
 }
 
@@ -231,10 +228,9 @@ static int page_anon_exclusive_sub_batch(int start_idx, int max_len,
  * retrieve sub-batches.
  */
 static void commit_anon_folio_batch(struct vm_area_struct *vma,
-		struct folio *folio, unsigned long addr, pte_t *ptep,
+		struct folio *folio, struct page *first_page, unsigned long addr, pte_t *ptep,
 		pte_t oldpte, pte_t ptent, int nr_ptes, struct mmu_gather *tlb)
 {
-	struct page *first_page = folio_page(folio, 0);
 	bool expected_anon_exclusive;
 	int sub_batch_idx = 0;
 	int len;
@@ -251,7 +247,7 @@ static void commit_anon_folio_batch(struct vm_area_struct *vma,
 }
 
 static void set_write_prot_commit_flush_ptes(struct vm_area_struct *vma,
-		struct folio *folio, unsigned long addr, pte_t *ptep,
+		struct folio *folio, struct page *page, unsigned long addr, pte_t *ptep,
 		pte_t oldpte, pte_t ptent, int nr_ptes, struct mmu_gather *tlb)
 {
 	bool set_write;
@@ -270,7 +266,7 @@ static void set_write_prot_commit_flush_ptes(struct vm_area_struct *vma,
 				       /* idx = */ 0, set_write, tlb);
 		return;
 	}
-	commit_anon_folio_batch(vma, folio, addr, ptep, oldpte, ptent, nr_ptes, tlb);
+	commit_anon_folio_batch(vma, folio, page, addr, ptep, oldpte, ptent, nr_ptes, tlb);
 }
 
 static long change_pte_range(struct mmu_gather *tlb,
@@ -305,15 +301,19 @@ static long change_pte_range(struct mmu_gather *tlb,
 			const fpb_t flags = FPB_RESPECT_SOFT_DIRTY | FPB_RESPECT_WRITE;
 			int max_nr_ptes = (end - addr) >> PAGE_SHIFT;
 			struct folio *folio = NULL;
+			struct page *page;
 			pte_t ptent;
 
+			page = vm_normal_page(vma, addr, oldpte);
+			if (page)
+				folio = page_folio(page);
 			/*
 			 * Avoid trapping faults against the zero or KSM
 			 * pages. See similar comment in change_huge_pmd.
 			 */
 			if (prot_numa) {
 				int ret = prot_numa_skip(vma, addr, oldpte, pte,
-							 target_node, &folio);
+							 target_node, folio);
 				if (ret) {
 
 					/* determine batch to skip */
@@ -323,9 +323,6 @@ static long change_pte_range(struct mmu_gather *tlb,
 				}
 			}
 
-			if (!folio)
-				folio = vm_normal_folio(vma, addr, oldpte);
-
 			nr_ptes = mprotect_folio_pte_batch(folio, pte, oldpte, max_nr_ptes, flags);
 
 			oldpte = modify_prot_start_ptes(vma, addr, pte, nr_ptes);
@@ -351,7 +348,7 @@ static long change_pte_range(struct mmu_gather *tlb,
 			 */
 			if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) &&
 			     !pte_write(ptent))
-				set_write_prot_commit_flush_ptes(vma, folio,
+				set_write_prot_commit_flush_ptes(vma, folio, page,
 				addr, pte, oldpte, ptent, nr_ptes, tlb);
 			else
 				prot_commit_flush_ptes(vma, addr, pte, oldpte, ptent,

mm/mremap.c

@@ -179,6 +179,10 @@ static int mremap_folio_pte_batch(struct vm_area_struct *vma, unsigned long addr
 	if (max_nr == 1)
 		return 1;
 
+	/* Avoid expensive folio lookup if we stand no chance of benefit. */
+	if (pte_batch_hint(ptep, pte) == 1)
+		return 1;
+
 	folio = vm_normal_folio(vma, addr, pte);
 	if (!folio || !folio_test_large(folio))
 		return 1;

mm/userfaultfd.c

@@ -1821,13 +1821,16 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start,
 			/* Check if we can move the pmd without splitting it. */
 			if (move_splits_huge_pmd(dst_addr, src_addr, src_start + len) ||
 			    !pmd_none(dst_pmdval)) {
-				struct folio *folio = pmd_folio(*src_pmd);
-
-				if (!folio || (!is_huge_zero_folio(folio) &&
-					       !PageAnonExclusive(&folio->page))) {
-					spin_unlock(ptl);
-					err = -EBUSY;
-					break;
+				/* Can be a migration entry */
+				if (pmd_present(*src_pmd)) {
+					struct folio *folio = pmd_folio(*src_pmd);
+
+					if (!is_huge_zero_folio(folio) &&
+					    !PageAnonExclusive(&folio->page)) {
+						spin_unlock(ptl);
+						err = -EBUSY;
+						break;
+					}
 				}
 
 				spin_unlock(ptl);

tools/testing/selftests/proc/proc-maps-race.c

@@ -202,11 +202,11 @@ static void print_first_lines(char *text, int nr)
 		int offs = end - text;
 
 		text[offs] = '\0';
-		printf(text);
+		printf("%s", text);
 		text[offs] = '\n';
 		printf("\n");
 	} else {
-		printf(text);
+		printf("%s", text);
 	}
 }
 
@@ -221,7 +221,7 @@ static void print_last_lines(char *text, int nr)
 		nr--;
 		start--;
 	}
-	printf(start);
+	printf("%s", start);
 }
 
 static void print_boundaries(const char *title, FIXTURE_DATA(proc_maps_race) *self)