linux.git/mm, branch v6.2-rc7

Merge tag 'mm-hotfixes-stable-2023-02-02-19-24-2' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2023-02-03T18:01:57+00:00

Pull misc fixes from Andrew Morton:
 "25 hotfixes, mainly for MM.  13 are cc:stable"

* tag 'mm-hotfixes-stable-2023-02-02-19-24-2' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (26 commits)
  mm: memcg: fix NULL pointer in mem_cgroup_track_foreign_dirty_slowpath()
  Kconfig.debug: fix the help description in SCHED_DEBUG
  mm/swapfile: add cond_resched() in get_swap_pages()
  mm: use stack_depot_early_init for kmemleak
  Squashfs: fix handling and sanity checking of xattr_ids count
  sh: define RUNTIME_DISCARD_EXIT
  highmem: round down the address passed to kunmap_flush_on_unmap()
  migrate: hugetlb: check for hugetlb shared PMD in node migration
  mm: hugetlb: proc: check for hugetlb shared PMD in /proc/PID/smaps
  mm/MADV_COLLAPSE: catch !none !huge !bad pmd lookups
  Revert "mm: kmemleak: alloc gray object for reserved region with direct map"
  freevxfs: Kconfig: fix spelling
  maple_tree: should get pivots boundary by type
  .mailmap: update e-mail address for Eugen Hristev
  mm, mremap: fix mremap() expanding for vma's with vm_ops->close()
  squashfs: harden sanity check in squashfs_read_xattr_id_table
  ia64: fix build error due to switch case label appearing next to declaration
  mm: multi-gen LRU: fix crash during cgroup migration
  Revert "mm: add nodes= arg to memory.reclaim"
  zsmalloc: fix a race with deferred_handles storing
  ...

mm/swapfile: add cond_resched() in get_swap_pages()

2023-02-01T00:44:10+00:00

The softlockup still occurs in get_swap_pages() under memory pressure.  64
CPU cores, 64GB memory, and 28 zram devices, the disksize of each zram
device is 50MB with same priority as si.  Use the stress-ng tool to
increase memory pressure, causing the system to oom frequently.

The plist_for_each_entry_safe() loops in get_swap_pages() could reach tens
of thousands of times to find available space (extreme case:
cond_resched() is not called in scan_swap_map_slots()).  Let's add
cond_resched() into get_swap_pages() when failed to find available space
to avoid softlockup.

Link: https://lkml.kernel.org/r/20230128094757.1060525-1-xialonglong1@huawei.com
Signed-off-by: Longlong Xia 
Reviewed-by: "Huang, Ying" 
Cc: Chen Wandun 
Cc: Huang Ying 
Cc: Kefeng Wang 
Cc: Nanyong Sun 
Cc: Hugh Dickins 
Cc: 
Signed-off-by: Andrew Morton

mm: use stack_depot_early_init for kmemleak

2023-02-01T00:44:10+00:00

Mirsad report the below error which is caused by stack_depot_init()
failure in kvcalloc.  Solve this by having stackdepot use
stack_depot_early_init().

On 1/4/23 17:08, Mirsad Goran Todorovac wrote:
I hate to bring bad news again, but there seems to be a problem with the output of /sys/kernel/debug/kmemleak:

[root@pc-mtodorov ~]# cat /sys/kernel/debug/kmemleak
unreferenced object 0xffff951c118568b0 (size 16):
comm "kworker/u12:2", pid 56, jiffies 4294893952 (age 4356.548s)
hex dump (first 16 bytes):
    6d 65 6d 73 74 69 63 6b 30 00 00 00 00 00 00 00 memstick0.......
    backtrace:
[root@pc-mtodorov ~]#

Apparently, backtrace of called functions on the stack is no longer
printed with the list of memory leaks.  This appeared on Lenovo desktop
10TX000VCR, with AlmaLinux 8.7 and BIOS version M22KT49A (11/10/2022) and
6.2-rc1 and 6.2-rc2 builds.  This worked on 6.1 with the same
CONFIG_KMEMLEAK=y and MGLRU enabled on a vanilla mainstream kernel from
Mr.  Torvalds' tree.  I don't know if this is deliberate feature for some
reason or a bug.  Please find attached the config, lshw and kmemleak
output.

[vbabka@suse.cz: remove stack_depot_init() call]
Link: https://lore.kernel.org/all/5272a819-ef74-65ff-be61-4d2d567337de@alu.unizg.hr/
Link: https://lkml.kernel.org/r/1674091345-14799-2-git-send-email-zhaoyang.huang@unisoc.com
Fixes: 56a61617dd22 ("mm: use stack_depot for recording kmemleak's backtrace")
Reported-by: Mirsad Todorovac 
Suggested-by: Vlastimil Babka 
Signed-off-by: Zhaoyang Huang 
Acked-by: Mike Rapoport (IBM) 
Acked-by: Catalin Marinas 
Acked-by: Vlastimil Babka 
Tested-by: Borislav Petkov (AMD) 
Cc: ke.wang 
Cc: Nathan Chancellor 
Cc: Peter Zijlstra (Intel) 
Signed-off-by: Andrew Morton

migrate: hugetlb: check for hugetlb shared PMD in node migration

2023-02-01T00:44:09+00:00

migrate_pages/mempolicy semantics state that CAP_SYS_NICE is required to
move pages shared with another process to a different node.  page_mapcount
> 1 is being used to determine if a hugetlb page is shared.  However, a
hugetlb page will have a mapcount of 1 if mapped by multiple processes via
a shared PMD.  As a result, hugetlb pages shared by multiple processes and
mapped with a shared PMD can be moved by a process without CAP_SYS_NICE.

To fix, check for a shared PMD if mapcount is 1.  If a shared PMD is found
consider the page shared.

Link: https://lkml.kernel.org/r/20230126222721.222195-3-mike.kravetz@oracle.com
Fixes: e2d8cf405525 ("migrate: add hugepage migration code to migrate_pages()")
Signed-off-by: Mike Kravetz 
Acked-by: Peter Xu 
Acked-by: David Hildenbrand 
Cc: James Houghton 
Cc: Matthew Wilcox 
Cc: Michal Hocko 
Cc: Muchun Song 
Cc: Naoya Horiguchi 
Cc: Vishal Moola (Oracle) 
Cc: Yang Shi 
Cc: 
Signed-off-by: Andrew Morton

mm/MADV_COLLAPSE: catch !none !huge !bad pmd lookups

2023-02-01T00:44:09+00:00

In commit 34488399fa08 ("mm/madvise: add file and shmem support to
MADV_COLLAPSE") we make the following change to find_pmd_or_thp_or_none():

	-       if (!pmd_present(pmde))
	-               return SCAN_PMD_NULL;
	+       if (pmd_none(pmde))
	+               return SCAN_PMD_NONE;

This was for-use by MADV_COLLAPSE file/shmem codepaths, where
MADV_COLLAPSE might identify a pte-mapped hugepage, only to have
khugepaged race-in, free the pte table, and clear the pmd.  Such codepaths
include:

A) If we find a suitably-aligned compound page of order HPAGE_PMD_ORDER
   already in the pagecache.
B) In retract_page_tables(), if we fail to grab mmap_lock for the target
   mm/address.

In these cases, collapse_pte_mapped_thp() really does expect a none (not
just !present) pmd, and we want to suitably identify that case separate
from the case where no pmd is found, or it's a bad-pmd (of course, many
things could happen once we drop mmap_lock, and the pmd could plausibly
undergo multiple transitions due to intervening fault, split, etc). 
Regardless, the code is prepared install a huge-pmd only when the existing
pmd entry is either a genuine pte-table-mapping-pmd, or the none-pmd.

However, the commit introduces a logical hole; namely, that we've allowed
!none- && !huge- && !bad-pmds to be classified as genuine
pte-table-mapping-pmds.  One such example that could leak through are swap
entries.  The pmd values aren't checked again before use in
pte_offset_map_lock(), which is expecting nothing less than a genuine
pte-table-mapping-pmd.

We want to put back the !pmd_present() check (below the pmd_none() check),
but need to be careful to deal with subtleties in pmd transitions and
treatments by various arch.

The issue is that __split_huge_pmd_locked() temporarily clears the present
bit (or otherwise marks the entry as invalid), but pmd_present() and
pmd_trans_huge() still need to return true while the pmd is in this
transitory state.  For example, x86's pmd_present() also checks the
_PAGE_PSE , riscv's version also checks the _PAGE_LEAF bit, and arm64 also
checks a PMD_PRESENT_INVALID bit.

Covering all 4 cases for x86 (all checks done on the same pmd value):

1) pmd_present() && pmd_trans_huge()
   All we actually know here is that the PSE bit is set. Either:
   a) We aren't racing with __split_huge_page(), and PRESENT or PROTNONE
      is set.
      => huge-pmd
   b) We are currently racing with __split_huge_page().  The danger here
      is that we proceed as-if we have a huge-pmd, but really we are
      looking at a pte-mapping-pmd.  So, what is the risk of this
      danger?

      The only relevant path is:

	madvise_collapse() -> collapse_pte_mapped_thp()

      Where we might just incorrectly report back "success", when really
      the memory isn't pmd-backed.  This is fine, since split could
      happen immediately after (actually) successful madvise_collapse().
      So, it should be safe to just assume huge-pmd here.

2) pmd_present() && !pmd_trans_huge()
   Either:
   a) PSE not set and either PRESENT or PROTNONE is.
      => pte-table-mapping pmd (or PROT_NONE)
   b) devmap.  This routine can be called immediately after
      unlocking/locking mmap_lock -- or called with no locks held (see
      khugepaged_scan_mm_slot()), so previous VMA checks have since been
      invalidated.

3) !pmd_present() && pmd_trans_huge()
  Not possible.

4) !pmd_present() && !pmd_trans_huge()
  Neither PRESENT nor PROTNONE set
  => not present

I've checked all archs that implement pmd_trans_huge() (arm64, riscv,
powerpc, longarch, x86, mips, s390) and this logic roughly translates
(though devmap treatment is unique to x86 and powerpc, and (3) doesn't
necessarily hold in general -- but that doesn't matter since
!pmd_present() always takes failure path).

Also, add a comment above find_pmd_or_thp_or_none() to help future
travelers reason about the validity of the code; namely, the possible
mutations that might happen out from under us, depending on how mmap_lock
is held (if at all).

Link: https://lkml.kernel.org/r/20230125225358.2576151-1-zokeefe@google.com
Fixes: 34488399fa08 ("mm/madvise: add file and shmem support to MADV_COLLAPSE")
Signed-off-by: Zach O'Keefe 
Reported-by: Hugh Dickins 
Reviewed-by: Yang Shi 
Cc: 
Signed-off-by: Andrew Morton

mm, mremap: fix mremap() expanding for vma's with vm_ops->close()

2023-02-01T00:44:08+00:00

Fabian has reported another regression in 6.1 due to ca3d76b0aa80 ("mm:
add merging after mremap resize").  The problem is that vma_merge() can
fail when vma has a vm_ops->close() method, causing is_mergeable_vma()
test to be negative.  This was happening for vma mapping a file from
fuse-overlayfs, which does have the method.  But when we are simply
expanding the vma, we never remove it due to the "merge" with the added
area, so the test should not prevent the expansion.

As a quick fix, check for such vmas and expand them using vma_adjust()
directly as was done before commit ca3d76b0aa80.  For a more robust long
term solution we should try to limit the check for vma_ops->close only to
cases that actually result in vma removal, so that no merge would be
prevented unnecessarily.

[akpm@linux-foundation.org: fix indenting whitespace, reflow comment]
Link: https://lkml.kernel.org/r/20230117101939.9753-1-vbabka@suse.cz
Fixes: ca3d76b0aa80 ("mm: add merging after mremap resize")
Signed-off-by: Vlastimil Babka 
Reported-by: Fabian Vogt 
  Link: https://bugzilla.suse.com/show_bug.cgi?id=1206359#c35
Tested-by: Fabian Vogt 
Cc: Jakub Matěna 
Cc: 
Signed-off-by: Andrew Morton

mm: multi-gen LRU: fix crash during cgroup migration

2023-02-01T00:44:08+00:00

lru_gen_migrate_mm() assumes lru_gen_add_mm() runs prior to itself.  This
isn't true for the following scenario:

    CPU 1                         CPU 2

  clone()
    cgroup_can_fork()
                                cgroup_procs_write()
    cgroup_post_fork()
                                  task_lock()
                                  lru_gen_migrate_mm()
                                  task_unlock()
    task_lock()
    lru_gen_add_mm()
    task_unlock()

And when the above happens, kernel crashes because of linked list
corruption (mm_struct->lru_gen.list).

Link: https://lore.kernel.org/r/20230115134651.30028-1-msizanoen@qtmlabs.xyz/
Link: https://lkml.kernel.org/r/20230116034405.2960276-1-yuzhao@google.com
Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks")
Signed-off-by: Yu Zhao 
Reported-by: msizanoen 
Tested-by: msizanoen 
Cc: 	[6.1+]
Signed-off-by: Andrew Morton

Revert "mm: add nodes= arg to memory.reclaim"

2023-02-01T00:44:07+00:00

This reverts commit 12a5d3955227b0d7e04fb793ccceeb2a1dd275c5.

Although it is recognized that a finer grained pro-active reclaim is
something we need and want the semantic of this implementation is really
ambiguous.

In a follow up discussion it became clear that there are two essential
usecases here.  One is to use memory.reclaim to pro-actively reclaim
memory and expectation is that the requested and reported amount of memory
is uncharged from the memcg.  Another usecase focuses on pro-active
demotion when the memory is merely shuffled around to demotion targets
while the overall charged memory stays unchanged.

The current implementation considers demoted pages as reclaimed and that
break both usecases.  [1] has tried to address the reporting part but
there are more issues with that summarized in [2] and follow up emails.

Let's revert the nodemask based extension of the memcg pro-active
reclaim for now until we settle with a more robust semantic.

[1] http://lkml.kernel.org/r/http://lkml.kernel.org/r/20221206023406.3182800-1-almasrymina@google.com
[2] http://lkml.kernel.org/r/Y5bsmpCyeryu3Zz1@dhcp22.suse.cz

Link: https://lkml.kernel.org/r/Y5xASNe1x8cusiTx@dhcp22.suse.cz
Fixes: 12a5d3955227b0d ("mm: add nodes= arg to memory.reclaim")
Signed-off-by: Michal Hocko 
Cc: Bagas Sanjaya 
Cc: Huang Ying 
Cc: Johannes Weiner 
Cc: Jonathan Corbet 
Cc: Mina Almasry 
Cc: Muchun Song 
Cc: Roman Gushchin 
Cc: Shakeel Butt 
Cc: Tejun Heo 
Cc: Wei Xu 
Cc: Yang Shi 
Cc: Yosry Ahmed 
Cc: zefan li 
Signed-off-by: Andrew Morton

zsmalloc: fix a race with deferred_handles storing

2023-02-01T00:44:07+00:00

Currently, there is a race between zs_free() and zs_reclaim_page():
zs_reclaim_page() finds a handle to an allocated object, but before the
eviction happens, an independent zs_free() call to the same handle could
come in and overwrite the object value stored at the handle with the last
deferred handle.  When zs_reclaim_page() finally gets to call the eviction
handler, it will see an invalid object value (i.e the previous deferred
handle instead of the original object value).

This race happens quite infrequently.  We only managed to produce it with
out-of-tree developmental code that triggers zsmalloc writeback with a
much higher frequency than usual.

This patch fixes this race by storing the deferred handle in the object
header instead.  We differentiate the deferred handle from the other two
cases (handle for allocated object, and linkage for free object) with a
new tag.  If zspage reclamation succeeds, we will free these deferred
handles by walking through the zspage objects.  On the other hand, if
zspage reclamation fails, we reconstruct the zspage freelist (with the
deferred handle tag and allocated tag) before trying again with the
reclamation.

[arnd@arndb.de: avoid unused-function warning]
  Link: https://lkml.kernel.org/r/20230117170507.2651972-1-arnd@kernel.org
Link: https://lkml.kernel.org/r/20230110231701.326724-1-nphamcs@gmail.com
Fixes: 9997bc017549 ("zsmalloc: implement writeback mechanism for zsmalloc")
Signed-off-by: Nhat Pham 
Signed-off-by: Arnd Bergmann 
Suggested-by: Johannes Weiner 
Cc: Dan Streetman 
Cc: Minchan Kim 
Cc: Nitin Gupta 
Cc: Sergey Senozhatsky 
Cc: Seth Jennings 
Cc: Vitaly Wool 
Signed-off-by: Andrew Morton

mm/khugepaged: fix ->anon_vma race

2023-02-01T00:44:07+00:00

If an ->anon_vma is attached to the VMA, collapse_and_free_pmd() requires
it to be locked.

Page table traversal is allowed under any one of the mmap lock, the
anon_vma lock (if the VMA is associated with an anon_vma), and the
mapping lock (if the VMA is associated with a mapping); and so to be
able to remove page tables, we must hold all three of them. 
retract_page_tables() bails out if an ->anon_vma is attached, but does
this check before holding the mmap lock (as the comment above the check
explains).

If we racily merged an existing ->anon_vma (shared with a child
process) from a neighboring VMA, subsequent rmap traversals on pages
belonging to the child will be able to see the page tables that we are
concurrently removing while assuming that nothing else can access them.

Repeat the ->anon_vma check once we hold the mmap lock to ensure that
there really is no concurrent page table access.

Hitting this bug causes a lockdep warning in collapse_and_free_pmd(),
in the line "lockdep_assert_held_write(&vma->anon_vma->root->rwsem)". 
It can also lead to use-after-free access.

Link: https://lore.kernel.org/linux-mm/CAG48ez3434wZBKFFbdx4M9j6eUwSUVPd4dxhzW_k_POneSDF+A@mail.gmail.com/
Link: https://lkml.kernel.org/r/20230111133351.807024-1-jannh@google.com
Fixes: f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages")
Signed-off-by: Jann Horn 
Reported-by: Zach O'Keefe 
Acked-by: Kirill A. Shutemov 
Reviewed-by: Yang Shi 
Cc: David Hildenbrand 
Cc: 
Signed-off-by: Andrew Morton