The quilt patch titled
Subject: mm/damon/stat: change last_refresh_jiffies to a global variable
has been removed from the -mm tree. Its filename was
mm-damon-stat-change-last_refresh_jiffies-to-a-global-variable.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: Quanmin Yan <yanquanmin1(a)huawei.com>
Subject: mm/damon/stat: change last_refresh_jiffies to a global variable
Date: Thu, 30 Oct 2025 10:07:45 +0800
Patch series "mm/damon: fixes for the jiffies-related issues", v2.
On 32-bit systems, the kernel initializes jiffies to "-5 minutes" to make
jiffies wrap bugs appear earlier. However, this may cause the
time_before() series of functions to return unexpected values, resulting
in DAMON not functioning as intended. Meanwhile, similar issues exist in
some specific user operation scenarios.
This patchset addresses these issues. The first patch is about the
DAMON_STAT module, and the second patch is about the core layer's sysfs.
This patch (of 2):
In DAMON_STAT's damon_stat_damon_call_fn(), time_before_eq() is used to
avoid unnecessarily frequent stat update.
On 32-bit systems, the kernel initializes jiffies to "-5 minutes" to make
jiffies wrap bugs appear earlier. However, this causes time_before_eq()
in DAMON_STAT to unexpectedly return true during the first 5 minutes after
boot on 32-bit systems (see [1] for more explanation, which fixes another
jiffies-related issue before). As a result, DAMON_STAT does not update
any monitoring results during that period, which becomes more confusing
when DAMON_STAT_ENABLED_DEFAULT is enabled.
There is also an issue unrelated to the system's word size[2]: if the user
stops DAMON_STAT just after last_refresh_jiffies is updated and restarts
it after 5 seconds or a longer delay, last_refresh_jiffies will retain an
older value, causing time_before_eq() to return false and the update to
happen earlier than expected.
Fix these issues by making last_refresh_jiffies a global variable and
initializing it each time DAMON_STAT is started.
Link: https://lkml.kernel.org/r/20251030020746.967174-2-yanquanmin1@huawei.com
Link: https://lkml.kernel.org/r/20250822025057.1740854-1-ekffu200098@gmail.com [1]
Link: https://lore.kernel.org/all/20251028143250.50144-1-sj@kernel.org/ [2]
Fixes: fabdd1e911da ("mm/damon/stat: calculate and expose estimated memory bandwidth")
Signed-off-by: Quanmin Yan <yanquanmin1(a)huawei.com>
Suggested-by: SeongJae Park <sj(a)kernel.org>
Reviewed-by: SeongJae Park <sj(a)kernel.org>
Cc: Kefeng Wang <wangkefeng.wang(a)huawei.com>
Cc: ze zuo <zuoze1(a)huawei.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/damon/stat.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
--- a/mm/damon/stat.c~mm-damon-stat-change-last_refresh_jiffies-to-a-global-variable
+++ a/mm/damon/stat.c
@@ -46,6 +46,8 @@ MODULE_PARM_DESC(aggr_interval_us,
static struct damon_ctx *damon_stat_context;
+static unsigned long damon_stat_last_refresh_jiffies;
+
static void damon_stat_set_estimated_memory_bandwidth(struct damon_ctx *c)
{
struct damon_target *t;
@@ -130,13 +132,12 @@ static void damon_stat_set_idletime_perc
static int damon_stat_damon_call_fn(void *data)
{
struct damon_ctx *c = data;
- static unsigned long last_refresh_jiffies;
/* avoid unnecessarily frequent stat update */
- if (time_before_eq(jiffies, last_refresh_jiffies +
+ if (time_before_eq(jiffies, damon_stat_last_refresh_jiffies +
msecs_to_jiffies(5 * MSEC_PER_SEC)))
return 0;
- last_refresh_jiffies = jiffies;
+ damon_stat_last_refresh_jiffies = jiffies;
aggr_interval_us = c->attrs.aggr_interval;
damon_stat_set_estimated_memory_bandwidth(c);
@@ -210,6 +211,8 @@ static int damon_stat_start(void)
err = damon_start(&damon_stat_context, 1, true);
if (err)
return err;
+
+ damon_stat_last_refresh_jiffies = jiffies;
call_control.data = damon_stat_context;
return damon_call(damon_stat_context, &call_control);
}
_
Patches currently in -mm which might be from yanquanmin1(a)huawei.com are
mm-damon-add-a-min_sz_region-parameter-to-damon_set_region_biggest_system_ram_default.patch
mm-damon-reclaim-use-min_sz_region-for-core-address-alignment-when-setting-regions.patch
The quilt patch titled
Subject: mm/mremap: honour writable bit in mremap pte batching
has been removed from the -mm tree. Its filename was
mm-mremap-honour-writable-bit-in-mremap-pte-batching.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: Dev Jain <dev.jain(a)arm.com>
Subject: mm/mremap: honour writable bit in mremap pte batching
Date: Tue, 28 Oct 2025 12:09:52 +0530
Currently mremap folio pte batch ignores the writable bit during figuring
out a set of similar ptes mapping the same folio. Suppose that the first
pte of the batch is writable while the others are not - set_ptes will end
up setting the writable bit on the other ptes, which is a violation of
mremap semantics. Therefore, use FPB_RESPECT_WRITE to check the writable
bit while determining the pte batch.
Link: https://lkml.kernel.org/r/20251028063952.90313-1-dev.jain@arm.com
Signed-off-by: Dev Jain <dev.jain(a)arm.com>
Fixes: f822a9a81a31 ("mm: optimize mremap() by PTE batching")
Reported-by: David Hildenbrand <david(a)redhat.com>
Debugged-by: David Hildenbrand <david(a)redhat.com>
Acked-by: David Hildenbrand <david(a)redhat.com>
Acked-by: Pedro Falcato <pfalcato(a)suse.de>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Cc: Barry Song <baohua(a)kernel.org>
Cc: Jann Horn <jannh(a)google.com>
Cc: Liam Howlett <liam.howlett(a)oracle.com>
Cc: Vlastimil Babka <vbabka(a)suse.cz>
Cc: <stable(a)vger.kernel.org> [6.17+]
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/mremap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/mremap.c~mm-mremap-honour-writable-bit-in-mremap-pte-batching
+++ a/mm/mremap.c
@@ -187,7 +187,7 @@ static int mremap_folio_pte_batch(struct
if (!folio || !folio_test_large(folio))
return 1;
- return folio_pte_batch(folio, ptep, pte, max_nr);
+ return folio_pte_batch_flags(folio, NULL, ptep, &pte, max_nr, FPB_RESPECT_WRITE);
}
static int move_ptes(struct pagetable_move_control *pmc,
_
Patches currently in -mm which might be from dev.jain(a)arm.com are
The quilt patch titled
Subject: gcov: add support for GCC 15
has been removed from the -mm tree. Its filename was
gcov-add-support-for-gcc-15.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: Peter Oberparleiter <oberpar(a)linux.ibm.com>
Subject: gcov: add support for GCC 15
Date: Tue, 28 Oct 2025 12:51:25 +0100
Using gcov on kernels compiled with GCC 15 results in truncated 16-byte
long .gcda files with no usable data. To fix this, update GCOV_COUNTERS
to match the value defined by GCC 15.
Tested with GCC 14.3.0 and GCC 15.2.0.
Link: https://lkml.kernel.org/r/20251028115125.1319410-1-oberpar@linux.ibm.com
Signed-off-by: Peter Oberparleiter <oberpar(a)linux.ibm.com>
Reported-by: Matthieu Baerts <matttbe(a)kernel.org>
Closes: https://github.com/linux-test-project/lcov/issues/445
Tested-by: Matthieu Baerts <matttbe(a)kernel.org>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
kernel/gcov/gcc_4_7.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/kernel/gcov/gcc_4_7.c~gcov-add-support-for-gcc-15
+++ a/kernel/gcov/gcc_4_7.c
@@ -18,7 +18,9 @@
#include <linux/mm.h>
#include "gcov.h"
-#if (__GNUC__ >= 14)
+#if (__GNUC__ >= 15)
+#define GCOV_COUNTERS 10
+#elif (__GNUC__ >= 14)
#define GCOV_COUNTERS 9
#elif (__GNUC__ >= 10)
#define GCOV_COUNTERS 8
_
Patches currently in -mm which might be from oberpar(a)linux.ibm.com are
The quilt patch titled
Subject: mm/mm_init: fix hash table order logging in alloc_large_system_hash()
has been removed from the -mm tree. Its filename was
mm-mm_init-fix-hash-table-order-logging-in-alloc_large_system_hash.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: "Isaac J. Manjarres" <isaacmanjarres(a)google.com>
Subject: mm/mm_init: fix hash table order logging in alloc_large_system_hash()
Date: Tue, 28 Oct 2025 12:10:12 -0700
When emitting the order of the allocation for a hash table,
alloc_large_system_hash() unconditionally subtracts PAGE_SHIFT from log
base 2 of the allocation size. This is not correct if the allocation size
is smaller than a page, and yields a negative value for the order as seen
below:
TCP established hash table entries: 32 (order: -4, 256 bytes, linear) TCP
bind hash table entries: 32 (order: -2, 1024 bytes, linear)
Use get_order() to compute the order when emitting the hash table
information to correctly handle cases where the allocation size is smaller
than a page:
TCP established hash table entries: 32 (order: 0, 256 bytes, linear) TCP
bind hash table entries: 32 (order: 0, 1024 bytes, linear)
Link: https://lkml.kernel.org/r/20251028191020.413002-1-isaacmanjarres@google.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Isaac J. Manjarres <isaacmanjarres(a)google.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt(a)kernel.org>
Reviewed-by: David Hildenbrand <david(a)redhat.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/mm_init.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/mm_init.c~mm-mm_init-fix-hash-table-order-logging-in-alloc_large_system_hash
+++ a/mm/mm_init.c
@@ -2469,7 +2469,7 @@ void *__init alloc_large_system_hash(con
panic("Failed to allocate %s hash table\n", tablename);
pr_info("%s hash table entries: %ld (order: %d, %lu bytes, %s)\n",
- tablename, 1UL << log2qty, ilog2(size) - PAGE_SHIFT, size,
+ tablename, 1UL << log2qty, get_order(size), size,
virt ? (huge ? "vmalloc hugepage" : "vmalloc") : "linear");
if (_hash_shift)
_
Patches currently in -mm which might be from isaacmanjarres(a)google.com are
The quilt patch titled
Subject: mm/truncate: unmap large folio on split failure
has been removed from the -mm tree. Its filename was
mm-truncate-unmap-large-folio-on-split-failure.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: Kiryl Shutsemau <kas(a)kernel.org>
Subject: mm/truncate: unmap large folio on split failure
Date: Mon, 27 Oct 2025 11:56:36 +0000
Accesses within VMA, but beyond i_size rounded up to PAGE_SIZE are
supposed to generate SIGBUS.
This behavior might not be respected on truncation.
During truncation, the kernel splits a large folio in order to reclaim
memory. As a side effect, it unmaps the folio and destroys PMD mappings
of the folio. The folio will be refaulted as PTEs and SIGBUS semantics
are preserved.
However, if the split fails, PMD mappings are preserved and the user will
not receive SIGBUS on any accesses within the PMD.
Unmap the folio on split failure. It will lead to refault as PTEs and
preserve SIGBUS semantics.
Make an exception for shmem/tmpfs that for long time intentionally mapped
with PMDs across i_size.
Link: https://lkml.kernel.org/r/20251027115636.82382-3-kirill@shutemov.name
Fixes: b9a8a4195c7d ("truncate,shmem: Handle truncates that split large folios")
Signed-off-by: Kiryl Shutsemau <kas(a)kernel.org>
Cc: Al Viro <viro(a)zeniv.linux.org.uk>
Cc: Baolin Wang <baolin.wang(a)linux.alibaba.com>
Cc: Christian Brauner <brauner(a)kernel.org>
Cc: "Darrick J. Wong" <djwong(a)kernel.org>
Cc: Dave Chinner <david(a)fromorbit.com>
Cc: David Hildenbrand <david(a)redhat.com>
Cc: Hugh Dickins <hughd(a)google.com>
Cc: Johannes Weiner <hannes(a)cmpxchg.org>
Cc: Liam Howlett <liam.howlett(a)oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Cc: Michal Hocko <mhocko(a)suse.com>
Cc: Mike Rapoport <rppt(a)kernel.org>
Cc: Rik van Riel <riel(a)surriel.com>
Cc: Shakeel Butt <shakeel.butt(a)linux.dev>
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>
---
mm/truncate.c | 35 +++++++++++++++++++++++++++++------
1 file changed, 29 insertions(+), 6 deletions(-)
--- a/mm/truncate.c~mm-truncate-unmap-large-folio-on-split-failure
+++ a/mm/truncate.c
@@ -177,6 +177,32 @@ int truncate_inode_folio(struct address_
return 0;
}
+static int try_folio_split_or_unmap(struct folio *folio, struct page *split_at,
+ unsigned long min_order)
+{
+ enum ttu_flags ttu_flags =
+ TTU_SYNC |
+ TTU_SPLIT_HUGE_PMD |
+ TTU_IGNORE_MLOCK;
+ int ret;
+
+ ret = try_folio_split_to_order(folio, split_at, min_order);
+
+ /*
+ * If the split fails, unmap the folio, so it will be refaulted
+ * with PTEs to respect SIGBUS semantics.
+ *
+ * Make an exception for shmem/tmpfs that for long time
+ * intentionally mapped with PMDs across i_size.
+ */
+ if (ret && !shmem_mapping(folio->mapping)) {
+ try_to_unmap(folio, ttu_flags);
+ WARN_ON(folio_mapped(folio));
+ }
+
+ return ret;
+}
+
/*
* Handle partial folios. The folio may be entirely within the
* range if a split has raced with us. If not, we zero the part of the
@@ -226,7 +252,7 @@ bool truncate_inode_partial_folio(struct
min_order = mapping_min_folio_order(folio->mapping);
split_at = folio_page(folio, PAGE_ALIGN_DOWN(offset) / PAGE_SIZE);
- if (!try_folio_split_to_order(folio, split_at, min_order)) {
+ if (!try_folio_split_or_unmap(folio, split_at, min_order)) {
/*
* try to split at offset + length to make sure folios within
* the range can be dropped, especially to avoid memory waste
@@ -250,13 +276,10 @@ bool truncate_inode_partial_folio(struct
if (!folio_trylock(folio2))
goto out;
- /*
- * make sure folio2 is large and does not change its mapping.
- * Its split result does not matter here.
- */
+ /* make sure folio2 is large and does not change its mapping */
if (folio_test_large(folio2) &&
folio2->mapping == folio->mapping)
- try_folio_split_to_order(folio2, split_at2, min_order);
+ try_folio_split_or_unmap(folio2, split_at2, min_order);
folio_unlock(folio2);
out:
_
Patches currently in -mm which might be from kas(a)kernel.org are
The quilt patch titled
Subject: mm/memory: do not populate page table entries beyond i_size
has been removed from the -mm tree. Its filename was
mm-memory-do-not-populate-page-table-entries-beyond-i_size.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: Kiryl Shutsemau <kas(a)kernel.org>
Subject: mm/memory: do not populate page table entries beyond i_size
Date: Mon, 27 Oct 2025 11:56:35 +0000
Patch series "Fix SIGBUS semantics with large folios", v3.
Accessing memory within a VMA, but beyond i_size rounded up to the next
page size, is supposed to generate SIGBUS.
Darrick reported[1] an xfstests regression in v6.18-rc1. generic/749
failed due to missing SIGBUS. This was caused by my recent changes that
try to fault in the whole folio where possible:
19773df031bc ("mm/fault: try to map the entire file folio in finish_fault()")
357b92761d94 ("mm/filemap: map entire large folio faultaround")
These changes did not consider i_size when setting up PTEs, leading to
xfstest breakage.
However, the problem has been present in the kernel for a long time -
since huge tmpfs was introduced in 2016. The kernel happily maps
PMD-sized folios as PMD without checking i_size. And huge=always tmpfs
allocates PMD-size folios on any writes.
I considered this corner case when I implemented a large tmpfs, and my
conclusion was that no one in their right mind should rely on receiving a
SIGBUS signal when accessing beyond i_size. I cannot imagine how it could
be useful for the workload.
But apparently filesystem folks care a lot about preserving strict SIGBUS
semantics.
Generic/749 was introduced last year with reference to POSIX, but no real
workloads were mentioned. It also acknowledged the tmpfs deviation from
the test case.
POSIX indeed says[3]:
References within the address range starting at pa and
continuing for len bytes to whole pages following the end of an
object shall result in delivery of a SIGBUS signal.
The patchset fixes the regression introduced by recent changes as well as
more subtle SIGBUS breakage due to split failure on truncation.
This patch (of 2):
Accesses within VMA, but beyond i_size rounded up to PAGE_SIZE are
supposed to generate SIGBUS.
Recent changes attempted to fault in full folio where possible. They did
not respect i_size, which led to populating PTEs beyond i_size and
breaking SIGBUS semantics.
Darrick reported generic/749 breakage because of this.
However, the problem existed before the recent changes. With huge=always
tmpfs, any write to a file leads to PMD-size allocation. Following the
fault-in of the folio will install PMD mapping regardless of i_size.
Fix filemap_map_pages() and finish_fault() to not install:
- PTEs beyond i_size;
- PMD mappings across i_size;
Make an exception for shmem/tmpfs that for long time intentionally
mapped with PMDs across i_size.
Link: https://lkml.kernel.org/r/20251027115636.82382-1-kirill@shutemov.name
Link: https://lkml.kernel.org/r/20251027115636.82382-2-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau <kas(a)kernel.org>
Fixes: 6795801366da ("xfs: Support large folios")
Reported-by: "Darrick J. Wong" <djwong(a)kernel.org>
Cc: Al Viro <viro(a)zeniv.linux.org.uk>
Cc: Baolin Wang <baolin.wang(a)linux.alibaba.com>
Cc: Christian Brauner <brauner(a)kernel.org>
Cc: Dave Chinner <david(a)fromorbit.com>
Cc: David Hildenbrand <david(a)redhat.com>
Cc: Hugh Dickins <hughd(a)google.com>
Cc: Johannes Weiner <hannes(a)cmpxchg.org>
Cc: Liam Howlett <liam.howlett(a)oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Cc: Michal Hocko <mhocko(a)suse.com>
Cc: Mike Rapoport <rppt(a)kernel.org>
Cc: Rik van Riel <riel(a)surriel.com>
Cc: Shakeel Butt <shakeel.butt(a)linux.dev>
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>
---
mm/filemap.c | 28 ++++++++++++++++++++--------
mm/memory.c | 20 +++++++++++++++++++-
2 files changed, 39 insertions(+), 9 deletions(-)
--- a/mm/filemap.c~mm-memory-do-not-populate-page-table-entries-beyond-i_size
+++ a/mm/filemap.c
@@ -3681,7 +3681,8 @@ skip:
static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
struct folio *folio, unsigned long start,
unsigned long addr, unsigned int nr_pages,
- unsigned long *rss, unsigned short *mmap_miss)
+ unsigned long *rss, unsigned short *mmap_miss,
+ bool can_map_large)
{
unsigned int ref_from_caller = 1;
vm_fault_t ret = 0;
@@ -3696,7 +3697,7 @@ static vm_fault_t filemap_map_folio_rang
* The folio must not cross VMA or page table boundary.
*/
addr0 = addr - start * PAGE_SIZE;
- if (folio_within_vma(folio, vmf->vma) &&
+ if (can_map_large && folio_within_vma(folio, vmf->vma) &&
(addr0 & PMD_MASK) == ((addr0 + folio_size(folio) - 1) & PMD_MASK)) {
vmf->pte -= start;
page -= start;
@@ -3811,13 +3812,27 @@ vm_fault_t filemap_map_pages(struct vm_f
unsigned long rss = 0;
unsigned int nr_pages = 0, folio_type;
unsigned short mmap_miss = 0, mmap_miss_saved;
+ bool can_map_large;
rcu_read_lock();
folio = next_uptodate_folio(&xas, mapping, end_pgoff);
if (!folio)
goto out;
- if (filemap_map_pmd(vmf, folio, start_pgoff)) {
+ file_end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE) - 1;
+ end_pgoff = min(end_pgoff, file_end);
+
+ /*
+ * Do not allow to map with PTEs beyond i_size and with PMD
+ * across i_size to preserve SIGBUS semantics.
+ *
+ * Make an exception for shmem/tmpfs that for long time
+ * intentionally mapped with PMDs across i_size.
+ */
+ can_map_large = shmem_mapping(mapping) ||
+ file_end >= folio_next_index(folio);
+
+ if (can_map_large && filemap_map_pmd(vmf, folio, start_pgoff)) {
ret = VM_FAULT_NOPAGE;
goto out;
}
@@ -3830,10 +3845,6 @@ vm_fault_t filemap_map_pages(struct vm_f
goto out;
}
- file_end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE) - 1;
- if (end_pgoff > file_end)
- end_pgoff = file_end;
-
folio_type = mm_counter_file(folio);
do {
unsigned long end;
@@ -3850,7 +3861,8 @@ vm_fault_t filemap_map_pages(struct vm_f
else
ret |= filemap_map_folio_range(vmf, folio,
xas.xa_index - folio->index, addr,
- nr_pages, &rss, &mmap_miss);
+ nr_pages, &rss, &mmap_miss,
+ can_map_large);
folio_unlock(folio);
} while ((folio = next_uptodate_folio(&xas, mapping, end_pgoff)) != NULL);
--- a/mm/memory.c~mm-memory-do-not-populate-page-table-entries-beyond-i_size
+++ a/mm/memory.c
@@ -65,6 +65,7 @@
#include <linux/gfp.h>
#include <linux/migrate.h>
#include <linux/string.h>
+#include <linux/shmem_fs.h>
#include <linux/memory-tiers.h>
#include <linux/debugfs.h>
#include <linux/userfaultfd_k.h>
@@ -5501,8 +5502,25 @@ fallback:
return ret;
}
+ if (!needs_fallback && vma->vm_file) {
+ struct address_space *mapping = vma->vm_file->f_mapping;
+ pgoff_t file_end;
+
+ file_end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
+
+ /*
+ * Do not allow to map with PTEs beyond i_size and with PMD
+ * across i_size to preserve SIGBUS semantics.
+ *
+ * Make an exception for shmem/tmpfs that for long time
+ * intentionally mapped with PMDs across i_size.
+ */
+ needs_fallback = !shmem_mapping(mapping) &&
+ file_end < folio_next_index(folio);
+ }
+
if (pmd_none(*vmf->pmd)) {
- if (folio_test_pmd_mappable(folio)) {
+ if (!needs_fallback && folio_test_pmd_mappable(folio)) {
ret = do_set_pmd(vmf, folio, page);
if (ret != VM_FAULT_FALLBACK)
return ret;
_
Patches currently in -mm which might be from kas(a)kernel.org are
The quilt patch titled
Subject: fs/proc: fix uaf in proc_readdir_de()
has been removed from the -mm tree. Its filename was
fs-proc-fix-uaf-in-proc_readdir_de.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 <albinwyang(a)tencent.com>
Subject: fs/proc: fix uaf in proc_readdir_de()
Date: Sat, 25 Oct 2025 10:42:33 +0800
Pde is erased from subdir rbtree through rb_erase(), but not set the node
to EMPTY, which may result in uaf access. We should use RB_CLEAR_NODE()
set the erased node to EMPTY, then pde_subdir_next() will return NULL to
avoid uaf access.
We found an uaf issue while using stress-ng testing, need to run testcase
getdent and tun in the same time. The steps of the issue is as follows:
1) use getdent to traverse dir /proc/pid/net/dev_snmp6/, and current
pde is tun3;
2) in the [time windows] unregister netdevice tun3 and tun2, and erase
them from rbtree. erase tun3 first, and then erase tun2. the
pde(tun2) will be released to slab;
3) continue to getdent process, then pde_subdir_next() will return
pde(tun2) which is released, it will case uaf access.
CPU 0 | CPU 1
-------------------------------------------------------------------------
traverse dir /proc/pid/net/dev_snmp6/ | unregister_netdevice(tun->dev) //tun3 tun2
sys_getdents64() |
iterate_dir() |
proc_readdir() |
proc_readdir_de() | snmp6_unregister_dev()
pde_get(de); | proc_remove()
read_unlock(&proc_subdir_lock); | remove_proc_subtree()
| write_lock(&proc_subdir_lock);
[time window] | rb_erase(&root->subdir_node, &parent->subdir);
| write_unlock(&proc_subdir_lock);
read_lock(&proc_subdir_lock); |
next = pde_subdir_next(de); |
pde_put(de); |
de = next; //UAF |
rbtree of dev_snmp6
|
pde(tun3)
/ \
NULL pde(tun2)
Link: https://lkml.kernel.org/r/20251025024233.158363-1-albin_yang@163.com
Signed-off-by: Wei Yang <albinwyang(a)tencent.com>
Cc: Al Viro <viro(a)zeniv.linux.org.uk>
Cc: Christian Brauner <brauner(a)kernel.org>
Cc: wangzijie <wangzijie1(a)honor.com>
Cc: Alexey Dobriyan <adobriyan(a)gmail.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
fs/proc/generic.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
--- a/fs/proc/generic.c~fs-proc-fix-uaf-in-proc_readdir_de
+++ a/fs/proc/generic.c
@@ -698,6 +698,12 @@ void pde_put(struct proc_dir_entry *pde)
}
}
+static void pde_erase(struct proc_dir_entry *pde, struct proc_dir_entry *parent)
+{
+ rb_erase(&pde->subdir_node, &parent->subdir);
+ RB_CLEAR_NODE(&pde->subdir_node);
+}
+
/*
* Remove a /proc entry and free it if it's not currently in use.
*/
@@ -720,7 +726,7 @@ void remove_proc_entry(const char *name,
WARN(1, "removing permanent /proc entry '%s'", de->name);
de = NULL;
} else {
- rb_erase(&de->subdir_node, &parent->subdir);
+ pde_erase(de, parent);
if (S_ISDIR(de->mode))
parent->nlink--;
}
@@ -764,7 +770,7 @@ int remove_proc_subtree(const char *name
root->parent->name, root->name);
return -EINVAL;
}
- rb_erase(&root->subdir_node, &parent->subdir);
+ pde_erase(root, parent);
de = root;
while (1) {
@@ -776,7 +782,7 @@ int remove_proc_subtree(const char *name
next->parent->name, next->name);
return -EINVAL;
}
- rb_erase(&next->subdir_node, &de->subdir);
+ pde_erase(next, de);
de = next;
continue;
}
_
Patches currently in -mm which might be from albinwyang(a)tencent.com are
The quilt patch titled
Subject: mm/huge_memory: preserve PG_has_hwpoisoned if a folio is split to >0 order
has been removed from the -mm tree. Its filename was
mm-huge_memory-preserve-pg_has_hwpoisoned-if-a-folio-is-split-to-0-order.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: Zi Yan <ziy(a)nvidia.com>
Subject: mm/huge_memory: preserve PG_has_hwpoisoned if a folio is split to >0 order
Date: Wed, 22 Oct 2025 23:05:21 -0400
folio split clears PG_has_hwpoisoned, but the flag should be preserved in
after-split folios containing pages with PG_hwpoisoned flag if the folio
is split to >0 order folios. Scan all pages in a to-be-split folio to
determine which after-split folios need the flag.
An alternatives is to change PG_has_hwpoisoned to PG_maybe_hwpoisoned to
avoid the scan and set it on all after-split folios, but resulting false
positive has undesirable negative impact. To remove false positive,
caller of folio_test_has_hwpoisoned() and folio_contain_hwpoisoned_page()
needs to do the scan. That might be causing a hassle for current and
future callers and more costly than doing the scan in the split code.
More details are discussed in [1].
This issue can be exposed via:
1. splitting a has_hwpoisoned folio to >0 order from debugfs interface;
2. truncating part of a has_hwpoisoned folio in
truncate_inode_partial_folio().
And later accesses to a hwpoisoned page could be possible due to the
missing has_hwpoisoned folio flag. This will lead to MCE errors.
Link: https://lore.kernel.org/all/CAHbLzkoOZm0PXxE9qwtF4gKR=cpRXrSrJ9V9Pm2DJexs98… [1]
Link: https://lkml.kernel.org/r/20251023030521.473097-1-ziy@nvidia.com
Fixes: c010d47f107f ("mm: thp: split huge page to any lower order pages")
Signed-off-by: Zi Yan <ziy(a)nvidia.com>
Acked-by: David Hildenbrand <david(a)redhat.com>
Reviewed-by: Yang Shi <yang(a)os.amperecomputing.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Reviewed-by: Lance Yang <lance.yang(a)linux.dev>
Reviewed-by: Miaohe Lin <linmiaohe(a)huawei.com>
Reviewed-by: Baolin Wang <baolin.wang(a)linux.alibaba.com>
Reviewed-by: Wei Yang <richard.weiyang(a)gmail.com>
Cc: Pankaj Raghav <kernel(a)pankajraghav.com>
Cc: Barry Song <baohua(a)kernel.org>
Cc: Dev Jain <dev.jain(a)arm.com>
Cc: Jane Chu <jane.chu(a)oracle.com>
Cc: Liam Howlett <liam.howlett(a)oracle.com>
Cc: Luis Chamberalin <mcgrof(a)kernel.org>
Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Cc: Naoya Horiguchi <nao.horiguchi(a)gmail.com>
Cc: Nico Pache <npache(a)redhat.com>
Cc: Ryan Roberts <ryan.roberts(a)arm.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/huge_memory.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)
--- a/mm/huge_memory.c~mm-huge_memory-preserve-pg_has_hwpoisoned-if-a-folio-is-split-to-0-order
+++ a/mm/huge_memory.c
@@ -3263,6 +3263,14 @@ bool can_split_folio(struct folio *folio
caller_pins;
}
+static bool page_range_has_hwpoisoned(struct page *page, long nr_pages)
+{
+ for (; nr_pages; page++, nr_pages--)
+ if (PageHWPoison(page))
+ return true;
+ return false;
+}
+
/*
* It splits @folio into @new_order folios and copies the @folio metadata to
* all the resulting folios.
@@ -3270,17 +3278,24 @@ bool can_split_folio(struct folio *folio
static void __split_folio_to_order(struct folio *folio, int old_order,
int new_order)
{
+ /* Scan poisoned pages when split a poisoned folio to large folios */
+ const bool handle_hwpoison = folio_test_has_hwpoisoned(folio) && new_order;
long new_nr_pages = 1 << new_order;
long nr_pages = 1 << old_order;
long i;
+ folio_clear_has_hwpoisoned(folio);
+
+ /* Check first new_nr_pages since the loop below skips them */
+ if (handle_hwpoison &&
+ page_range_has_hwpoisoned(folio_page(folio, 0), new_nr_pages))
+ folio_set_has_hwpoisoned(folio);
/*
* Skip the first new_nr_pages, since the new folio from them have all
* the flags from the original folio.
*/
for (i = new_nr_pages; i < nr_pages; i += new_nr_pages) {
struct page *new_head = &folio->page + i;
-
/*
* Careful: new_folio is not a "real" folio before we cleared PageTail.
* Don't pass it around before clear_compound_head().
@@ -3322,6 +3337,10 @@ static void __split_folio_to_order(struc
(1L << PG_dirty) |
LRU_GEN_MASK | LRU_REFS_MASK));
+ if (handle_hwpoison &&
+ page_range_has_hwpoisoned(new_head, new_nr_pages))
+ folio_set_has_hwpoisoned(new_folio);
+
new_folio->mapping = folio->mapping;
new_folio->index = folio->index + i;
@@ -3422,8 +3441,6 @@ static int __split_unmapped_folio(struct
if (folio_test_anon(folio))
mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1);
- folio_clear_has_hwpoisoned(folio);
-
/*
* split to new_order one order at a time. For uniform split,
* folio is split to new_order directly.
_
Patches currently in -mm which might be from ziy(a)nvidia.com are
mm-huge_memory-fix-folio-split-check-for-anon-folios-in-swapcache.patch
mm-huge_memory-add-split_huge_page_to_order.patch
mm-memory-failure-improve-large-block-size-folio-handling.patch
mm-huge_memory-fix-kernel-doc-comments-for-folio_split-and-related.patch
mm-huge_memory-fix-kernel-doc-comments-for-folio_split-and-related-fix.patch
mm-huge_memory-fix-kernel-doc-comments-for-folio_split-and-related-fix-2.patch
migrate-optimise-alloc_migration_target-fix.patch