The quilt patch titled
Subject: mm/huge_memory: fix NULL pointer deference when splitting folio
has been removed from the -mm tree. Its filename was
mm-huge_memory-fix-null-pointer-deference-when-splitting-folio.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Wei Yang <richard.weiyang(a)gmail.com>
Subject: mm/huge_memory: fix NULL pointer deference when splitting folio
Date: Wed, 19 Nov 2025 23:53:02 +0000
Commit c010d47f107f ("mm: thp: split huge page to any lower order pages")
introduced an early check on the folio's order via mapping->flags before
proceeding with the split work.
This check introduced a bug: for shmem folios in the swap cache and
truncated folios, the mapping pointer can be NULL. Accessing
mapping->flags in this state leads directly to a NULL pointer dereference.
This commit fixes the issue by moving the check for mapping != NULL before
any attempt to access mapping->flags.
Link: https://lkml.kernel.org/r/20251119235302.24773-1-richard.weiyang@gmail.com
Fixes: c010d47f107f ("mm: thp: split huge page to any lower order pages")
Signed-off-by: Wei Yang <richard.weiyang(a)gmail.com>
Reviewed-by: Zi Yan <ziy(a)nvidia.com>
Acked-by: David Hildenbrand (Red Hat) <david(a)kernel.org>
Reviewed-by: Baolin Wang <baolin.wang(a)linux.alibaba.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/huge_memory.c | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)
--- a/mm/huge_memory.c~mm-huge_memory-fix-null-pointer-deference-when-splitting-folio
+++ a/mm/huge_memory.c
@@ -3619,6 +3619,16 @@ static int __folio_split(struct folio *f
if (folio != page_folio(split_at) || folio != page_folio(lock_at))
return -EINVAL;
+ /*
+ * Folios that just got truncated cannot get split. Signal to the
+ * caller that there was a race.
+ *
+ * TODO: this will also currently refuse shmem folios that are in the
+ * swapcache.
+ */
+ if (!is_anon && !folio->mapping)
+ return -EBUSY;
+
if (new_order >= folio_order(folio))
return -EINVAL;
@@ -3659,18 +3669,6 @@ static int __folio_split(struct folio *f
gfp_t gfp;
mapping = folio->mapping;
-
- /* Truncated ? */
- /*
- * TODO: add support for large shmem folio in swap cache.
- * When shmem is in swap cache, mapping is NULL and
- * folio_test_swapcache() is true.
- */
- if (!mapping) {
- ret = -EBUSY;
- goto out;
- }
-
min_order = mapping_min_folio_order(folio->mapping);
if (new_order < min_order) {
ret = -EINVAL;
_
Patches currently in -mm which might be from richard.weiyang(a)gmail.com are
mm-huge_memory-add-pmd-folio-to-ds_queue-in-do_huge_zero_wp_pmd.patch
mm-khugepaged-unify-pmd-folio-installation-with-map_anon_folio_pmd.patch
mm-huge_memory-only-get-folio_order-once-during-__folio_split.patch
mm-huge_memory-introduce-enum-split_type-for-clarity.patch
mm-huge_memory-merge-uniform_split_supported-and-non_uniform_split_supported.patch
mm-khugepaged-remove-redundant-clearing-of-struct-collapse_control.patch
mm-khugepaged-continue-to-collapse-on-scan_pmd_none.patch
mm-khugepaged-unify-scan_pmd_none-and-scan_pmd_null-into-scan_no_pte_table.patch
The quilt patch titled
Subject: selftests/mm: fix division-by-zero in uffd-unit-tests
has been removed from the -mm tree. Its filename was
selftests-mm-fix-division-by-zero-in-uffd-unit-tests.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Carlos Llamas <cmllamas(a)google.com>
Subject: selftests/mm: fix division-by-zero in uffd-unit-tests
Date: Thu, 13 Nov 2025 03:46:22 +0000
Commit 4dfd4bba8578 ("selftests/mm/uffd: refactor non-composite global
vars into struct") moved some of the operations previously implemented in
uffd_setup_environment() earlier in the main test loop.
The calculation of nr_pages, which involves a division by page_size, now
occurs before checking that default_huge_page_size() returns a non-zero
This leads to a division-by-zero error on systems with !CONFIG_HUGETLB.
Fix this by relocating the non-zero page_size check before the nr_pages
calculation, as it was originally implemented.
Link: https://lkml.kernel.org/r/20251113034623.3127012-1-cmllamas@google.com
Fixes: 4dfd4bba8578 ("selftests/mm/uffd: refactor non-composite global vars into struct")
Signed-off-by: Carlos Llamas <cmllamas(a)google.com>
Acked-by: David Hildenbrand (Red Hat) <david(a)kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt(a)kernel.org>
Reviewed-by: Ujwal Kundur <ujwal.kundur(a)gmail.com>
Cc: Brendan Jackman <jackmanb(a)google.com>
Cc: Liam Howlett <liam.howlett(a)oracle.com>
Cc: Michal Hocko <mhocko(a)suse.com>
Cc: Peter Xu <peterx(a)redhat.com>
Cc: Shuah Khan <shuah(a)kernel.org>
Cc: Suren Baghdasaryan <surenb(a)google.com>
Cc: Vlastimil Babka <vbabka(a)suse.cz>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
tools/testing/selftests/mm/uffd-unit-tests.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
--- a/tools/testing/selftests/mm/uffd-unit-tests.c~selftests-mm-fix-division-by-zero-in-uffd-unit-tests
+++ a/tools/testing/selftests/mm/uffd-unit-tests.c
@@ -1758,10 +1758,15 @@ int main(int argc, char *argv[])
uffd_test_ops = mem_type->mem_ops;
uffd_test_case_ops = test->test_case_ops;
- if (mem_type->mem_flag & (MEM_HUGETLB_PRIVATE | MEM_HUGETLB))
+ if (mem_type->mem_flag & (MEM_HUGETLB_PRIVATE | MEM_HUGETLB)) {
gopts.page_size = default_huge_page_size();
- else
+ if (gopts.page_size == 0) {
+ uffd_test_skip("huge page size is 0, feature missing?");
+ continue;
+ }
+ } else {
gopts.page_size = psize();
+ }
/* Ensure we have at least 2 pages */
gopts.nr_pages = MAX(UFFD_TEST_MEM_SIZE, gopts.page_size * 2)
@@ -1776,12 +1781,6 @@ int main(int argc, char *argv[])
continue;
uffd_test_start("%s on %s", test->name, mem_type->name);
- if ((mem_type->mem_flag == MEM_HUGETLB ||
- mem_type->mem_flag == MEM_HUGETLB_PRIVATE) &&
- (default_huge_page_size() == 0)) {
- uffd_test_skip("huge page size is 0, feature missing?");
- continue;
- }
if (!uffd_feature_supported(test)) {
uffd_test_skip("feature missing");
continue;
_
Patches currently in -mm which might be from cmllamas(a)google.com are
The quilt patch titled
Subject: mm/memfd: fix information leak in hugetlb folios
has been removed from the -mm tree. Its filename was
mm-memfd-fix-information-leak-in-hugetlb-folios.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Deepanshu Kartikey <kartikey406(a)gmail.com>
Subject: mm/memfd: fix information leak in hugetlb folios
Date: Wed, 12 Nov 2025 20:20:34 +0530
When allocating hugetlb folios for memfd, three initialization steps are
missing:
1. Folios are not zeroed, leading to kernel memory disclosure to userspace
2. Folios are not marked uptodate before adding to page cache
3. hugetlb_fault_mutex is not taken before hugetlb_add_to_page_cache()
The memfd allocation path bypasses the normal page fault handler
(hugetlb_no_page) which would handle all of these initialization steps.
This is problematic especially for udmabuf use cases where folios are
pinned and directly accessed by userspace via DMA.
Fix by matching the initialization pattern used in hugetlb_no_page():
- Zero the folio using folio_zero_user() which is optimized for huge pages
- Mark it uptodate with folio_mark_uptodate()
- Take hugetlb_fault_mutex before adding to page cache to prevent races
The folio_zero_user() change also fixes a potential security issue where
uninitialized kernel memory could be disclosed to userspace through read()
or mmap() operations on the memfd.
Link: https://lkml.kernel.org/r/20251112145034.2320452-1-kartikey406@gmail.com
Fixes: 89c1905d9c14 ("mm/gup: introduce memfd_pin_folios() for pinning memfd folios")
Signed-off-by: Deepanshu Kartikey <kartikey406(a)gmail.com>
Reported-by: syzbot+f64019ba229e3a5c411b(a)syzkaller.appspotmail.com
Link: https://lore.kernel.org/all/20251112031631.2315651-1-kartikey406@gmail.com/ [v1]
Closes: https://syzkaller.appspot.com/bug?extid=f64019ba229e3a5c411b
Suggested-by: Oscar Salvador <osalvador(a)suse.de>
Suggested-by: David Hildenbrand <david(a)redhat.com>
Tested-by: syzbot+f64019ba229e3a5c411b(a)syzkaller.appspotmail.com
Acked-by: Oscar Salvador <osalvador(a)suse.de>
Acked-by: David Hildenbrand (Red Hat) <david(a)kernel.org>
Acked-by: Hugh Dickins <hughd(a)google.com>
Cc: Vivek Kasireddy <vivek.kasireddy(a)intel.com>
Cc: Jason Gunthorpe <jgg(a)nvidia.com>
Cc: Jason Gunthorpe <jgg(a)nvidia.com> (v2)
Cc: Christoph Hellwig <hch(a)lst.de> (v6)
Cc: Dave Airlie <airlied(a)redhat.com>
Cc: Gerd Hoffmann <kraxel(a)redhat.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/memfd.c | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)
--- a/mm/memfd.c~mm-memfd-fix-information-leak-in-hugetlb-folios
+++ a/mm/memfd.c
@@ -96,9 +96,36 @@ struct folio *memfd_alloc_folio(struct f
NULL,
gfp_mask);
if (folio) {
+ u32 hash;
+
+ /*
+ * Zero the folio to prevent information leaks to userspace.
+ * Use folio_zero_user() which is optimized for huge/gigantic
+ * pages. Pass 0 as addr_hint since this is not a faulting path
+ * and we don't have a user virtual address yet.
+ */
+ folio_zero_user(folio, 0);
+
+ /*
+ * Mark the folio uptodate before adding to page cache,
+ * as required by filemap.c and other hugetlb paths.
+ */
+ __folio_mark_uptodate(folio);
+
+ /*
+ * Serialize hugepage allocation and instantiation to prevent
+ * races with concurrent allocations, as required by all other
+ * callers of hugetlb_add_to_page_cache().
+ */
+ hash = hugetlb_fault_mutex_hash(memfd->f_mapping, idx);
+ mutex_lock(&hugetlb_fault_mutex_table[hash]);
+
err = hugetlb_add_to_page_cache(folio,
memfd->f_mapping,
idx);
+
+ mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+
if (err) {
folio_put(folio);
goto err_unresv;
_
Patches currently in -mm which might be from kartikey406(a)gmail.com are
The quilt patch titled
Subject: mm: swap: remove duplicate nr_swap_pages decrement in get_swap_page_of_type()
has been removed from the -mm tree. Its filename was
mm-swap-remove-duplicate-nr_swap_pages-decrement-in-get_swap_page_of_type.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Youngjun Park <youngjun.park(a)lge.com>
Subject: mm: swap: remove duplicate nr_swap_pages decrement in get_swap_page_of_type()
Date: Sun, 2 Nov 2025 17:24:56 +0900
After commit 4f78252da887, nr_swap_pages is decremented in
swap_range_alloc(). Since cluster_alloc_swap_entry() calls
swap_range_alloc() internally, the decrement in get_swap_page_of_type()
causes double-decrementing.
As a representative userspace-visible runtime example of the impact,
/proc/meminfo reports increasingly inaccurate SwapFree values. The
discrepancy grows with each swap allocation, and during hibernation
when large amounts of memory are written to swap, the reported value
can deviate significantly from actual available swap space, misleading
users and monitoring tools.
Remove the duplicate decrement.
Link: https://lkml.kernel.org/r/20251102082456.79807-1-youngjun.park@lge.com
Fixes: 4f78252da887 ("mm: swap: move nr_swap_pages counter decrement from folio_alloc_swap() to swap_range_alloc()")
Signed-off-by: Youngjun Park <youngjun.park(a)lge.com>
Acked-by: Chris Li <chrisl(a)kernel.org>
Reviewed-by: Barry Song <baohua(a)kernel.org>
Reviewed-by: Kairui Song <kasong(a)tencent.com>
Acked-by: Nhat Pham <nphamcs(a)gmail.com>
Cc: Baoquan He <bhe(a)redhat.com>
Cc: Kemeng Shi <shikemeng(a)huaweicloud.com>
Cc: <stable(a)vger.kernel.org> [6.17+]
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/swapfile.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
--- a/mm/swapfile.c~mm-swap-remove-duplicate-nr_swap_pages-decrement-in-get_swap_page_of_type
+++ a/mm/swapfile.c
@@ -2005,10 +2005,8 @@ swp_entry_t get_swap_page_of_type(int ty
local_lock(&percpu_swap_cluster.lock);
offset = cluster_alloc_swap_entry(si, 0, 1);
local_unlock(&percpu_swap_cluster.lock);
- if (offset) {
+ if (offset)
entry = swp_entry(si->type, offset);
- atomic_long_dec(&nr_swap_pages);
- }
}
put_swap_device(si);
}
_
Patches currently in -mm which might be from youngjun.park(a)lge.com are
mm-swap-fix-wrong-plist-empty-check-in-swap_alloc_slow.patch
mm-swap-fix-memory-leak-in-setup_clusters-error-path.patch
mm-swap-use-swp_solidstate-to-determine-if-swap-is-rotational.patch
mm-swap-remove-redundant-comment-for-read_swap_cache_async.patch
mm-swap-change-swap_alloc_slow-to-void.patch
mm-swap-remove-scan_swap_map_slots-references-from-comments.patch