From: Hugh Dickins <hughd(a)google.com>
Subject: mm/thp: fix __split_huge_pmd_locked() on shmem migration entry
Patch series "mm/thp: fix THP splitting unmap BUGs and related", v10.
Here is v2 batch of long-standing THP bug fixes that I had not got around
to sending before, but prompted now by Wang Yugui's report
https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/
Wang Yugui has tested a rollup of these fixes applied to 5.10.39, and they
have done no harm, but have *not* fixed that issue: something more is
needed and I have no idea of what.
This patch (of 7):
Stressing huge tmpfs page migration racing hole punch often crashed on the
VM_BUG_ON(!pmd_present) in pmdp_huge_clear_flush(), with DEBUG_VM=y
kernel; or shortly afterwards, on a bad dereference in
__split_huge_pmd_locked() when DEBUG_VM=n. They forgot to allow for pmd
migration entries in the non-anonymous case.
Full disclosure: those particular experiments were on a kernel with more
relaxed mmap_lock and i_mmap_rwsem locking, and were not repeated on the
vanilla kernel: it is conceivable that stricter locking happens to avoid
those cases, or makes them less likely; but __split_huge_pmd_locked()
already allowed for pmd migration entries when handling anonymous THPs, so
this commit brings the shmem and file THP handling into line.
And while there: use old_pmd rather than _pmd, as in the following blocks;
and make it clearer to the eye that the !vma_is_anonymous() block is
self-contained, making an early return after accounting for unmapping.
Link: https://lkml.kernel.org/r/af88612-1473-2eaa-903-8d1a448b26@google.com
Link: https://lkml.kernel.org/r/dd221a99-efb3-cd1d-6256-7e646af29314@google.com
Fixes: e71769ae5260 ("mm: enable thp migration for shmem thp")
Signed-off-by: Hugh Dickins <hughd(a)google.com>
Cc: Kirill A. Shutemov <kirill.shutemov(a)linux.intel.com>
Cc: Yang Shi <shy828301(a)gmail.com>
Cc: Wang Yugui <wangyugui(a)e16-tech.com>
Cc: "Matthew Wilcox (Oracle)" <willy(a)infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi(a)nec.com>
Cc: Alistair Popple <apopple(a)nvidia.com>
Cc: Ralph Campbell <rcampbell(a)nvidia.com>
Cc: Zi Yan <ziy(a)nvidia.com>
Cc: Miaohe Lin <linmiaohe(a)huawei.com>
Cc: Minchan Kim <minchan(a)kernel.org>
Cc: Jue Wang <juew(a)google.com>
Cc: Peter Xu <peterx(a)redhat.com>
Cc: Jan Kara <jack(a)suse.cz>
Cc: Shakeel Butt <shakeelb(a)google.com>
Cc: Oscar Salvador <osalvador(a)suse.de>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/huge_memory.c | 27 ++++++++++++++++++---------
mm/pgtable-generic.c | 5 ++---
2 files changed, 20 insertions(+), 12 deletions(-)
--- a/mm/huge_memory.c~mm-thp-fix-__split_huge_pmd_locked-on-shmem-migration-entry
+++ a/mm/huge_memory.c
@@ -2044,7 +2044,7 @@ static void __split_huge_pmd_locked(stru
count_vm_event(THP_SPLIT_PMD);
if (!vma_is_anonymous(vma)) {
- _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
+ old_pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
/*
* We are going to unmap this huge page. So
* just go ahead and zap it
@@ -2053,16 +2053,25 @@ static void __split_huge_pmd_locked(stru
zap_deposited_table(mm, pmd);
if (vma_is_special_huge(vma))
return;
- page = pmd_page(_pmd);
- if (!PageDirty(page) && pmd_dirty(_pmd))
- set_page_dirty(page);
- if (!PageReferenced(page) && pmd_young(_pmd))
- SetPageReferenced(page);
- page_remove_rmap(page, true);
- put_page(page);
+ if (unlikely(is_pmd_migration_entry(old_pmd))) {
+ swp_entry_t entry;
+
+ entry = pmd_to_swp_entry(old_pmd);
+ page = migration_entry_to_page(entry);
+ } else {
+ page = pmd_page(old_pmd);
+ if (!PageDirty(page) && pmd_dirty(old_pmd))
+ set_page_dirty(page);
+ if (!PageReferenced(page) && pmd_young(old_pmd))
+ SetPageReferenced(page);
+ page_remove_rmap(page, true);
+ put_page(page);
+ }
add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
return;
- } else if (pmd_trans_huge(*pmd) && is_huge_zero_pmd(*pmd)) {
+ }
+
+ if (pmd_trans_huge(*pmd) && is_huge_zero_pmd(*pmd)) {
/*
* FIXME: Do we want to invalidate secondary mmu by calling
* mmu_notifier_invalidate_range() see comments below inside
--- a/mm/pgtable-generic.c~mm-thp-fix-__split_huge_pmd_locked-on-shmem-migration-entry
+++ a/mm/pgtable-generic.c
@@ -135,9 +135,8 @@ pmd_t pmdp_huge_clear_flush(struct vm_ar
{
pmd_t pmd;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
- VM_BUG_ON(!pmd_present(*pmdp));
- /* Below assumes pmd_present() is true */
- VM_BUG_ON(!pmd_trans_huge(*pmdp) && !pmd_devmap(*pmdp));
+ VM_BUG_ON(pmd_present(*pmdp) && !pmd_trans_huge(*pmdp) &&
+ !pmd_devmap(*pmdp));
pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp);
flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
return pmd;
_
From: Xu Yu <xuyu(a)linux.alibaba.com>
Subject: mm, thp: use head page in __migration_entry_wait()
We notice that hung task happens in a corner but practical scenario when
CONFIG_PREEMPT_NONE is enabled, as follows.
Process 0 Process 1 Process 2..Inf
split_huge_page_to_list
unmap_page
split_huge_pmd_address
__migration_entry_wait(head)
__migration_entry_wait(tail)
remap_page (roll back)
remove_migration_ptes
rmap_walk_anon
cond_resched
Where __migration_entry_wait(tail) is occurred in kernel space, e.g.,
copy_to_user in fstat, which will immediately fault again without
rescheduling, and thus occupy the cpu fully.
When there are too many processes performing __migration_entry_wait on
tail page, remap_page will never be done after cond_resched.
This makes __migration_entry_wait operate on the compound head page, thus
waits for remap_page to complete, whether the THP is split successfully or
roll back.
Note that put_and_wait_on_page_locked helps to drop the page reference
acquired with get_page_unless_zero, as soon as the page is on the wait
queue, before actually waiting. So splitting the THP is only prevented
for a brief interval.
Link: https://lkml.kernel.org/r/b9836c1dd522e903891760af9f0c86a2cce987eb.16231440…
Fixes: ba98828088ad ("thp: add option to setup migration entries during PMD split")
Suggested-by: Hugh Dickins <hughd(a)google.com>
Signed-off-by: Gang Deng <gavin.dg(a)linux.alibaba.com>
Signed-off-by: Xu Yu <xuyu(a)linux.alibaba.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov(a)linux.intel.com>
Acked-by: Hugh Dickins <hughd(a)google.com>
Cc: Matthew Wilcox <willy(a)infradead.org>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/migrate.c | 1 +
1 file changed, 1 insertion(+)
--- a/mm/migrate.c~mm-thp-use-head-page-in-__migration_entry_wait
+++ a/mm/migrate.c
@@ -295,6 +295,7 @@ void __migration_entry_wait(struct mm_st
goto out;
page = migration_entry_to_page(entry);
+ page = compound_head(page);
/*
* Once page cache replacement of page migration started, page_count
_
From: Pingfan Liu <kernelfans(a)gmail.com>
Subject: crash_core, vmcoreinfo: append 'SECTION_SIZE_BITS' to vmcoreinfo
As mentioned in kernel commit 1d50e5d0c505 ("crash_core, vmcoreinfo:
Append 'MAX_PHYSMEM_BITS' to vmcoreinfo"), SECTION_SIZE_BITS in the
formula:
#define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS)
Besides SECTIONS_SHIFT, SECTION_SIZE_BITS is also used to calculate
PAGES_PER_SECTION in makedumpfile just like kernel.
Unfortunately, this arch-dependent macro SECTION_SIZE_BITS changes, e.g.
recently in kernel commit f0b13ee23241 ("arm64/sparsemem: reduce
SECTION_SIZE_BITS"). But user space wants a stable interface to get this
info. Such info is impossible to be deduced from a crashdump vmcore.
Hence append SECTION_SIZE_BITS to vmcoreinfo.
Link: https://lkml.kernel.org/r/20210608103359.84907-1-kernelfans@gmail.com
Link: http://lists.infradead.org/pipermail/kexec/2021-June/022676.html
Signed-off-by: Pingfan Liu <kernelfans(a)gmail.com>
Acked-by: Baoquan He <bhe(a)redhat.com>
Cc: Bhupesh Sharma <bhupesh.sharma(a)linaro.org>
Cc: Kazuhito Hagio <k-hagio(a)ab.jp.nec.com>
Cc: Dave Young <dyoung(a)redhat.com>
Cc: Boris Petkov <bp(a)alien8.de>
Cc: Ingo Molnar <mingo(a)kernel.org>
Cc: Thomas Gleixner <tglx(a)linutronix.de>
Cc: James Morse <james.morse(a)arm.com>
Cc: Mark Rutland <mark.rutland(a)arm.com>
Cc: Will Deacon <will(a)kernel.org>
Cc: Catalin Marinas <catalin.marinas(a)arm.com>
Cc: Michael Ellerman <mpe(a)ellerman.id.au>
Cc: Paul Mackerras <paulus(a)samba.org>
Cc: Benjamin Herrenschmidt <benh(a)kernel.crashing.org>
Cc: Dave Anderson <anderson(a)redhat.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
kernel/crash_core.c | 1 +
1 file changed, 1 insertion(+)
--- a/kernel/crash_core.c~crash_core-vmcoreinfo-append-section_size_bits-to-vmcoreinfo
+++ a/kernel/crash_core.c
@@ -464,6 +464,7 @@ static int __init crash_save_vmcoreinfo_
VMCOREINFO_LENGTH(mem_section, NR_SECTION_ROOTS);
VMCOREINFO_STRUCT_SIZE(mem_section);
VMCOREINFO_OFFSET(mem_section, section_mem_map);
+ VMCOREINFO_NUMBER(SECTION_SIZE_BITS);
VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
#endif
VMCOREINFO_STRUCT_SIZE(page);
_
From: Mike Kravetz <mike.kravetz(a)oracle.com>
Subject: mm/hugetlb: expand restore_reserve_on_error functionality
The routine restore_reserve_on_error is called to restore reservation
information when an error occurs after page allocation. The routine
alloc_huge_page modifies the mapping reserve map and potentially the
reserve count during allocation. If code calling alloc_huge_page
encounters an error after allocation and needs to free the page, the
reservation information needs to be adjusted.
Currently, restore_reserve_on_error only takes action on pages for which
the reserve count was adjusted(HPageRestoreReserve flag). There is
nothing wrong with these adjustments. However, alloc_huge_page ALWAYS
modifies the reserve map during allocation even if the reserve count is
not adjusted. This can cause issues as observed during development of
this patch [1].
One specific series of operations causing an issue is:
- Create a shared hugetlb mapping
Reservations for all pages created by default
- Fault in a page in the mapping
Reservation exists so reservation count is decremented
- Punch a hole in the file/mapping at index previously faulted
Reservation and any associated pages will be removed
- Allocate a page to fill the hole
No reservation entry, so reserve count unmodified
Reservation entry added to map by alloc_huge_page
- Error after allocation and before instantiating the page
Reservation entry remains in map
- Allocate a page to fill the hole
Reservation entry exists, so decrement reservation count
This will cause a reservation count underflow as the reservation count was
decremented twice for the same index.
A user would observe a very large number for HugePages_Rsvd in
/proc/meminfo. This would also likely cause subsequent allocations of
hugetlb pages to fail as it would 'appear' that all pages are reserved.
This sequence of operations is unlikely to happen, however they were
easily reproduced and observed using hacked up code as described in [1].
Address the issue by having the routine restore_reserve_on_error take
action on pages where HPageRestoreReserve is not set. In this case, we
need to remove any reserve map entry created by alloc_huge_page. A new
helper routine vma_del_reservation assists with this operation.
There are three callers of alloc_huge_page which do not currently call
restore_reserve_on error before freeing a page on error paths. Add those
missing calls.
[1] https://lore.kernel.org/linux-mm/20210528005029.88088-1-almasrymina@google.…
Link: https://lkml.kernel.org/r/20210607204510.22617-1-mike.kravetz@oracle.com
Fixes: 96b96a96ddee ("mm/hugetlb: fix huge page reservation leak in private mapping error paths"
Signed-off-by: Mike Kravetz <mike.kravetz(a)oracle.com>
Reviewed-by: Mina Almasry <almasrymina(a)google.com>
Cc: Axel Rasmussen <axelrasmussen(a)google.com>
Cc: Peter Xu <peterx(a)redhat.com>
Cc: Muchun Song <songmuchun(a)bytedance.com>
Cc: Michal Hocko <mhocko(a)suse.com>
Cc: Naoya Horiguchi <naoya.horiguchi(a)nec.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
fs/hugetlbfs/inode.c | 1
include/linux/hugetlb.h | 2
mm/hugetlb.c | 122 ++++++++++++++++++++++++++++++--------
3 files changed, 101 insertions(+), 24 deletions(-)
--- a/fs/hugetlbfs/inode.c~mm-hugetlb-expand-restore_reserve_on_error-functionality
+++ a/fs/hugetlbfs/inode.c
@@ -735,6 +735,7 @@ static long hugetlbfs_fallocate(struct f
__SetPageUptodate(page);
error = huge_add_to_page_cache(page, mapping, index);
if (unlikely(error)) {
+ restore_reserve_on_error(h, &pseudo_vma, addr, page);
put_page(page);
mutex_unlock(&hugetlb_fault_mutex_table[hash]);
goto out;
--- a/include/linux/hugetlb.h~mm-hugetlb-expand-restore_reserve_on_error-functionality
+++ a/include/linux/hugetlb.h
@@ -610,6 +610,8 @@ struct page *alloc_huge_page_vma(struct
unsigned long address);
int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
pgoff_t idx);
+void restore_reserve_on_error(struct hstate *h, struct vm_area_struct *vma,
+ unsigned long address, struct page *page);
/* arch callback */
int __init __alloc_bootmem_huge_page(struct hstate *h);
--- a/mm/hugetlb.c~mm-hugetlb-expand-restore_reserve_on_error-functionality
+++ a/mm/hugetlb.c
@@ -2121,12 +2121,18 @@ out:
* be restored when a newly allocated huge page must be freed. It is
* to be called after calling vma_needs_reservation to determine if a
* reservation exists.
+ *
+ * vma_del_reservation is used in error paths where an entry in the reserve
+ * map was created during huge page allocation and must be removed. It is to
+ * be called after calling vma_needs_reservation to determine if a reservation
+ * exists.
*/
enum vma_resv_mode {
VMA_NEEDS_RESV,
VMA_COMMIT_RESV,
VMA_END_RESV,
VMA_ADD_RESV,
+ VMA_DEL_RESV,
};
static long __vma_reservation_common(struct hstate *h,
struct vm_area_struct *vma, unsigned long addr,
@@ -2170,11 +2176,21 @@ static long __vma_reservation_common(str
ret = region_del(resv, idx, idx + 1);
}
break;
+ case VMA_DEL_RESV:
+ if (vma->vm_flags & VM_MAYSHARE) {
+ region_abort(resv, idx, idx + 1, 1);
+ ret = region_del(resv, idx, idx + 1);
+ } else {
+ ret = region_add(resv, idx, idx + 1, 1, NULL, NULL);
+ /* region_add calls of range 1 should never fail. */
+ VM_BUG_ON(ret < 0);
+ }
+ break;
default:
BUG();
}
- if (vma->vm_flags & VM_MAYSHARE)
+ if (vma->vm_flags & VM_MAYSHARE || mode == VMA_DEL_RESV)
return ret;
/*
* We know private mapping must have HPAGE_RESV_OWNER set.
@@ -2222,25 +2238,39 @@ static long vma_add_reservation(struct h
return __vma_reservation_common(h, vma, addr, VMA_ADD_RESV);
}
+static long vma_del_reservation(struct hstate *h,
+ struct vm_area_struct *vma, unsigned long addr)
+{
+ return __vma_reservation_common(h, vma, addr, VMA_DEL_RESV);
+}
+
/*
- * This routine is called to restore a reservation on error paths. In the
- * specific error paths, a huge page was allocated (via alloc_huge_page)
- * and is about to be freed. If a reservation for the page existed,
- * alloc_huge_page would have consumed the reservation and set
- * HPageRestoreReserve in the newly allocated page. When the page is freed
- * via free_huge_page, the global reservation count will be incremented if
- * HPageRestoreReserve is set. However, free_huge_page can not adjust the
- * reserve map. Adjust the reserve map here to be consistent with global
- * reserve count adjustments to be made by free_huge_page.
- */
-static void restore_reserve_on_error(struct hstate *h,
- struct vm_area_struct *vma, unsigned long address,
- struct page *page)
+ * This routine is called to restore reservation information on error paths.
+ * It should ONLY be called for pages allocated via alloc_huge_page(), and
+ * the hugetlb mutex should remain held when calling this routine.
+ *
+ * It handles two specific cases:
+ * 1) A reservation was in place and the page consumed the reservation.
+ * HPageRestoreReserve is set in the page.
+ * 2) No reservation was in place for the page, so HPageRestoreReserve is
+ * not set. However, alloc_huge_page always updates the reserve map.
+ *
+ * In case 1, free_huge_page later in the error path will increment the
+ * global reserve count. But, free_huge_page does not have enough context
+ * to adjust the reservation map. This case deals primarily with private
+ * mappings. Adjust the reserve map here to be consistent with global
+ * reserve count adjustments to be made by free_huge_page. Make sure the
+ * reserve map indicates there is a reservation present.
+ *
+ * In case 2, simply undo reserve map modifications done by alloc_huge_page.
+ */
+void restore_reserve_on_error(struct hstate *h, struct vm_area_struct *vma,
+ unsigned long address, struct page *page)
{
- if (unlikely(HPageRestoreReserve(page))) {
- long rc = vma_needs_reservation(h, vma, address);
+ long rc = vma_needs_reservation(h, vma, address);
- if (unlikely(rc < 0)) {
+ if (HPageRestoreReserve(page)) {
+ if (unlikely(rc < 0))
/*
* Rare out of memory condition in reserve map
* manipulation. Clear HPageRestoreReserve so that
@@ -2253,16 +2283,57 @@ static void restore_reserve_on_error(str
* accounting of reserve counts.
*/
ClearHPageRestoreReserve(page);
- } else if (rc) {
- rc = vma_add_reservation(h, vma, address);
- if (unlikely(rc < 0))
+ else if (rc)
+ (void)vma_add_reservation(h, vma, address);
+ else
+ vma_end_reservation(h, vma, address);
+ } else {
+ if (!rc) {
+ /*
+ * This indicates there is an entry in the reserve map
+ * added by alloc_huge_page. We know it was added
+ * before the alloc_huge_page call, otherwise
+ * HPageRestoreReserve would be set on the page.
+ * Remove the entry so that a subsequent allocation
+ * does not consume a reservation.
+ */
+ rc = vma_del_reservation(h, vma, address);
+ if (rc < 0)
/*
- * See above comment about rare out of
- * memory condition.
+ * VERY rare out of memory condition. Since
+ * we can not delete the entry, set
+ * HPageRestoreReserve so that the reserve
+ * count will be incremented when the page
+ * is freed. This reserve will be consumed
+ * on a subsequent allocation.
*/
- ClearHPageRestoreReserve(page);
+ SetHPageRestoreReserve(page);
+ } else if (rc < 0) {
+ /*
+ * Rare out of memory condition from
+ * vma_needs_reservation call. Memory allocation is
+ * only attempted if a new entry is needed. Therefore,
+ * this implies there is not an entry in the
+ * reserve map.
+ *
+ * For shared mappings, no entry in the map indicates
+ * no reservation. We are done.
+ */
+ if (!(vma->vm_flags & VM_MAYSHARE))
+ /*
+ * For private mappings, no entry indicates
+ * a reservation is present. Since we can
+ * not add an entry, set SetHPageRestoreReserve
+ * on the page so reserve count will be
+ * incremented when freed. This reserve will
+ * be consumed on a subsequent allocation.
+ */
+ SetHPageRestoreReserve(page);
} else
- vma_end_reservation(h, vma, address);
+ /*
+ * No reservation present, do nothing
+ */
+ vma_end_reservation(h, vma, address);
}
}
@@ -4037,6 +4108,8 @@ again:
spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
entry = huge_ptep_get(src_pte);
if (!pte_same(src_pte_old, entry)) {
+ restore_reserve_on_error(h, vma, addr,
+ new);
put_page(new);
/* dst_entry won't change as in child */
goto again;
@@ -5006,6 +5079,7 @@ out_release_unlock:
if (vm_shared || is_continue)
unlock_page(page);
out_release_nounlock:
+ restore_reserve_on_error(h, dst_vma, dst_addr, page);
put_page(page);
goto out;
}
_
From: Kees Cook <keescook(a)chromium.org>
Subject: mm/slub: actually fix freelist pointer vs redzoning
It turns out that SLUB redzoning ("slub_debug=Z") checks from
s->object_size rather than from s->inuse (which is normally bumped to make
room for the freelist pointer), so a cache created with an object size
less than 24 would have the freelist pointer written beyond
s->object_size, causing the redzone to be corrupted by the freelist
pointer. This was very visible with "slub_debug=ZF":
BUG test (Tainted: G B ): Right Redzone overwritten
-----------------------------------------------------------------------------
INFO: 0xffff957ead1c05de-0xffff957ead1c05df @offset=1502. First byte 0x1a instead of 0xbb
INFO: Slab 0xffffef3950b47000 objects=170 used=170 fp=0x0000000000000000 flags=0x8000000000000200
INFO: Object 0xffff957ead1c05d8 @offset=1496 fp=0xffff957ead1c0620
Redzone (____ptrval____): bb bb bb bb bb bb bb bb ........
Object (____ptrval____): 00 00 00 00 00 f6 f4 a5 ........
Redzone (____ptrval____): 40 1d e8 1a aa @....
Padding (____ptrval____): 00 00 00 00 00 00 00 00 ........
Adjust the offset to stay within s->object_size.
(Note that no caches of in this size range are known to exist in the
kernel currently.)
Link: https://lkml.kernel.org/r/20210608183955.280836-4-keescook@chromium.org
Link: https://lore.kernel.org/linux-mm/20200807160627.GA1420741@elver.google.com/
Link: https://lore.kernel.org/lkml/0f7dd7b2-7496-5e2d-9488-2ec9f8e90441@suse.cz/F…: 89b83f282d8b (slub: avoid redzone when choosing freepointer location)
Link: https://lore.kernel.org/lkml/CANpmjNOwZ5VpKQn+SYWovTkFB4VsT-RPwyENBmaK0dLcp…
Signed-off-by: Kees Cook <keescook(a)chromium.org>
Reported-by: Marco Elver <elver(a)google.com>
Reported-by: "Lin, Zhenpeng" <zplin(a)psu.edu>
Tested-by: Marco Elver <elver(a)google.com>
Acked-by: Vlastimil Babka <vbabka(a)suse.cz>
Cc: Christoph Lameter <cl(a)linux.com>
Cc: David Rientjes <rientjes(a)google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim(a)lge.com>
Cc: Pekka Enberg <penberg(a)kernel.org>
Cc: Roman Gushchin <guro(a)fb.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/slub.c | 14 +++-----------
1 file changed, 3 insertions(+), 11 deletions(-)
--- a/mm/slub.c~mm-slub-actually-fix-freelist-pointer-vs-redzoning
+++ a/mm/slub.c
@@ -3689,7 +3689,6 @@ static int calculate_sizes(struct kmem_c
{
slab_flags_t flags = s->flags;
unsigned int size = s->object_size;
- unsigned int freepointer_area;
unsigned int order;
/*
@@ -3698,13 +3697,6 @@ static int calculate_sizes(struct kmem_c
* the possible location of the free pointer.
*/
size = ALIGN(size, sizeof(void *));
- /*
- * This is the area of the object where a freepointer can be
- * safely written. If redzoning adds more to the inuse size, we
- * can't use that portion for writing the freepointer, so
- * s->offset must be limited within this for the general case.
- */
- freepointer_area = size;
#ifdef CONFIG_SLUB_DEBUG
/*
@@ -3730,7 +3722,7 @@ static int calculate_sizes(struct kmem_c
/*
* With that we have determined the number of bytes in actual use
- * by the object. This is the potential offset to the free pointer.
+ * by the object and redzoning.
*/
s->inuse = size;
@@ -3753,13 +3745,13 @@ static int calculate_sizes(struct kmem_c
*/
s->offset = size;
size += sizeof(void *);
- } else if (freepointer_area > sizeof(void *)) {
+ } else {
/*
* Store freelist pointer near middle of object to keep
* it away from the edges of the object to avoid small
* sized over/underflows from neighboring allocations.
*/
- s->offset = ALIGN(freepointer_area / 2, sizeof(void *));
+ s->offset = ALIGN_DOWN(s->object_size / 2, sizeof(void *));
}
#ifdef CONFIG_SLUB_DEBUG
_
From: Kees Cook <keescook(a)chromium.org>
Subject: mm/slub: fix redzoning for small allocations
The redzone area for SLUB exists between s->object_size and s->inuse
(which is at least the word-aligned object_size). If a cache were created
with an object_size smaller than sizeof(void *), the in-object stored
freelist pointer would overwrite the redzone (e.g. with boot param
"slub_debug=ZF"):
BUG test (Tainted: G B ): Right Redzone overwritten
-----------------------------------------------------------------------------
INFO: 0xffff957ead1c05de-0xffff957ead1c05df @offset=1502. First byte 0x1a instead of 0xbb
INFO: Slab 0xffffef3950b47000 objects=170 used=170 fp=0x0000000000000000 flags=0x8000000000000200
INFO: Object 0xffff957ead1c05d8 @offset=1496 fp=0xffff957ead1c0620
Redzone (____ptrval____): bb bb bb bb bb bb bb bb ........
Object (____ptrval____): f6 f4 a5 40 1d e8 ...@..
Redzone (____ptrval____): 1a aa ..
Padding (____ptrval____): 00 00 00 00 00 00 00 00 ........
Store the freelist pointer out of line when object_size is smaller than
sizeof(void *) and redzoning is enabled.
Additionally remove the "smaller than sizeof(void *)" check under
CONFIG_DEBUG_VM in kmem_cache_sanity_check() as it is now redundant:
SLAB and SLOB both handle small sizes.
(Note that no caches within this size range are known to exist in the
kernel currently.)
Link: https://lkml.kernel.org/r/20210608183955.280836-3-keescook@chromium.org
Fixes: 81819f0fc828 ("SLUB core")
Signed-off-by: Kees Cook <keescook(a)chromium.org>
Acked-by: Vlastimil Babka <vbabka(a)suse.cz>
Cc: Christoph Lameter <cl(a)linux.com>
Cc: David Rientjes <rientjes(a)google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim(a)lge.com>
Cc: "Lin, Zhenpeng" <zplin(a)psu.edu>
Cc: Marco Elver <elver(a)google.com>
Cc: Pekka Enberg <penberg(a)kernel.org>
Cc: Roman Gushchin <guro(a)fb.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/slab_common.c | 3 +--
mm/slub.c | 8 +++++---
2 files changed, 6 insertions(+), 5 deletions(-)
--- a/mm/slab_common.c~mm-slub-fix-redzoning-for-small-allocations
+++ a/mm/slab_common.c
@@ -97,8 +97,7 @@ EXPORT_SYMBOL(kmem_cache_size);
#ifdef CONFIG_DEBUG_VM
static int kmem_cache_sanity_check(const char *name, unsigned int size)
{
- if (!name || in_interrupt() || size < sizeof(void *) ||
- size > KMALLOC_MAX_SIZE) {
+ if (!name || in_interrupt() || size > KMALLOC_MAX_SIZE) {
pr_err("kmem_cache_create(%s) integrity check failed\n", name);
return -EINVAL;
}
--- a/mm/slub.c~mm-slub-fix-redzoning-for-small-allocations
+++ a/mm/slub.c
@@ -3734,15 +3734,17 @@ static int calculate_sizes(struct kmem_c
*/
s->inuse = size;
- if (((flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) ||
- s->ctor)) {
+ if ((flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) ||
+ ((flags & SLAB_RED_ZONE) && s->object_size < sizeof(void *)) ||
+ s->ctor) {
/*
* Relocate free pointer after the object if it is not
* permitted to overwrite the first word of the object on
* kmem_cache_free.
*
* This is the case if we do RCU, have a constructor or
- * destructor or are poisoning the objects.
+ * destructor, are poisoning the objects, or are
+ * redzoning an object smaller than sizeof(void *).
*
* The assumption that s->offset >= s->inuse means free
* pointer is outside of the object is used in the
_
From: Naoya Horiguchi <naoya.horiguchi(a)nec.com>
Subject: mm,hwpoison: fix race with hugetlb page allocation
When hugetlb page fault (under overcommitting situation) and
memory_failure() race, VM_BUG_ON_PAGE() is triggered by the following
race:
CPU0: CPU1:
gather_surplus_pages()
page = alloc_surplus_huge_page()
memory_failure_hugetlb()
get_hwpoison_page(page)
__get_hwpoison_page(page)
get_page_unless_zero(page)
zero = put_page_testzero(page)
VM_BUG_ON_PAGE(!zero, page)
enqueue_huge_page(h, page)
put_page(page)
__get_hwpoison_page() only checks the page refcount before taking an
additional one for memory error handling, which is not enough because
there's a time window where compound pages have non-zero refcount during
hugetlb page initialization.
So make __get_hwpoison_page() check page status a bit more for hugetlb
pages with get_hwpoison_huge_page(). Checking hugetlb-specific flags
under hugetlb_lock makes sure that the hugetlb page is not transitive.
It's notable that another new function, HWPoisonHandlable(), is helpful to
prevent a race against other transitive page states (like a generic
compound page just before PageHuge becomes true).
Link: https://lkml.kernel.org/r/20210603233632.2964832-2-nao.horiguchi@gmail.com
Fixes: ead07f6a867b ("mm/memory-failure: introduce get_hwpoison_page() for consistent refcount handling")
Signed-off-by: Naoya Horiguchi <naoya.horiguchi(a)nec.com>
Reported-by: Muchun Song <songmuchun(a)bytedance.com>
Acked-by: Mike Kravetz <mike.kravetz(a)oracle.com>
Cc: Oscar Salvador <osalvador(a)suse.de>
Cc: Michal Hocko <mhocko(a)suse.com>
Cc: Tony Luck <tony.luck(a)intel.com>
Cc: <stable(a)vger.kernel.org> [5.12+]
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
include/linux/hugetlb.h | 6 ++++++
mm/hugetlb.c | 15 +++++++++++++++
mm/memory-failure.c | 29 +++++++++++++++++++++++++++--
3 files changed, 48 insertions(+), 2 deletions(-)
--- a/include/linux/hugetlb.h~mmhwpoison-fix-race-with-hugetlb-page-allocation
+++ a/include/linux/hugetlb.h
@@ -149,6 +149,7 @@ bool hugetlb_reserve_pages(struct inode
long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
long freed);
bool isolate_huge_page(struct page *page, struct list_head *list);
+int get_hwpoison_huge_page(struct page *page, bool *hugetlb);
void putback_active_hugepage(struct page *page);
void move_hugetlb_state(struct page *oldpage, struct page *newpage, int reason);
void free_huge_page(struct page *page);
@@ -339,6 +340,11 @@ static inline bool isolate_huge_page(str
return false;
}
+static inline int get_hwpoison_huge_page(struct page *page, bool *hugetlb)
+{
+ return 0;
+}
+
static inline void putback_active_hugepage(struct page *page)
{
}
--- a/mm/hugetlb.c~mmhwpoison-fix-race-with-hugetlb-page-allocation
+++ a/mm/hugetlb.c
@@ -5857,6 +5857,21 @@ unlock:
return ret;
}
+int get_hwpoison_huge_page(struct page *page, bool *hugetlb)
+{
+ int ret = 0;
+
+ *hugetlb = false;
+ spin_lock_irq(&hugetlb_lock);
+ if (PageHeadHuge(page)) {
+ *hugetlb = true;
+ if (HPageFreed(page) || HPageMigratable(page))
+ ret = get_page_unless_zero(page);
+ }
+ spin_unlock_irq(&hugetlb_lock);
+ return ret;
+}
+
void putback_active_hugepage(struct page *page)
{
spin_lock_irq(&hugetlb_lock);
--- a/mm/memory-failure.c~mmhwpoison-fix-race-with-hugetlb-page-allocation
+++ a/mm/memory-failure.c
@@ -949,6 +949,17 @@ static int page_action(struct page_state
return (result == MF_RECOVERED || result == MF_DELAYED) ? 0 : -EBUSY;
}
+/*
+ * Return true if a page type of a given page is supported by hwpoison
+ * mechanism (while handling could fail), otherwise false. This function
+ * does not return true for hugetlb or device memory pages, so it's assumed
+ * to be called only in the context where we never have such pages.
+ */
+static inline bool HWPoisonHandlable(struct page *page)
+{
+ return PageLRU(page) || __PageMovable(page);
+}
+
/**
* __get_hwpoison_page() - Get refcount for memory error handling:
* @page: raw error page (hit by memory error)
@@ -959,8 +970,22 @@ static int page_action(struct page_state
static int __get_hwpoison_page(struct page *page)
{
struct page *head = compound_head(page);
+ int ret = 0;
+ bool hugetlb = false;
+
+ ret = get_hwpoison_huge_page(head, &hugetlb);
+ if (hugetlb)
+ return ret;
+
+ /*
+ * This check prevents from calling get_hwpoison_unless_zero()
+ * for any unsupported type of page in order to reduce the risk of
+ * unexpected races caused by taking a page refcount.
+ */
+ if (!HWPoisonHandlable(head))
+ return 0;
- if (!PageHuge(head) && PageTransHuge(head)) {
+ if (PageTransHuge(head)) {
/*
* Non anonymous thp exists only in allocation/free time. We
* can't handle such a case correctly, so let's give it up.
@@ -1017,7 +1042,7 @@ try_again:
ret = -EIO;
}
} else {
- if (PageHuge(p) || PageLRU(p) || __PageMovable(p)) {
+ if (PageHuge(p) || HWPoisonHandlable(p)) {
ret = 1;
} else {
/*
_