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Message-ID: <573a823565734e1eac3aa128fb9d3506ec918a72.1745940843.git.agordeev@linux.ibm.com>
Date: Tue, 29 Apr 2025 18:08:41 +0200
From: Alexander Gordeev <agordeev@...ux.ibm.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Andrey Ryabinin <ryabinin.a.a@...il.com>,
Daniel Axtens <dja@...ens.net>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
kasan-dev@...glegroups.com, linux-s390@...r.kernel.org,
stable@...r.kernel.org
Subject: [PATCH v3 1/1] kasan: Avoid sleepable page allocation from atomic context
apply_to_pte_range() enters the lazy MMU mode and then invokes
kasan_populate_vmalloc_pte() callback on each page table walk
iteration. However, the callback can go into sleep when trying
to allocate a single page, e.g. if an architecutre disables
preemption on lazy MMU mode enter.
On s390 if make arch_enter_lazy_mmu_mode() -> preempt_enable()
and arch_leave_lazy_mmu_mode() -> preempt_disable(), such crash
occurs:
[ 553.332108] preempt_count: 1, expected: 0
[ 553.332117] no locks held by multipathd/2116.
[ 553.332128] CPU: 24 PID: 2116 Comm: multipathd Kdump: loaded Tainted:
[ 553.332139] Hardware name: IBM 3931 A01 701 (LPAR)
[ 553.332146] Call Trace:
[ 553.332152] [<00000000158de23a>] dump_stack_lvl+0xfa/0x150
[ 553.332167] [<0000000013e10d12>] __might_resched+0x57a/0x5e8
[ 553.332178] [<00000000144eb6c2>] __alloc_pages+0x2ba/0x7c0
[ 553.332189] [<00000000144d5cdc>] __get_free_pages+0x2c/0x88
[ 553.332198] [<00000000145663f6>] kasan_populate_vmalloc_pte+0x4e/0x110
[ 553.332207] [<000000001447625c>] apply_to_pte_range+0x164/0x3c8
[ 553.332218] [<000000001448125a>] apply_to_pmd_range+0xda/0x318
[ 553.332226] [<000000001448181c>] __apply_to_page_range+0x384/0x768
[ 553.332233] [<0000000014481c28>] apply_to_page_range+0x28/0x38
[ 553.332241] [<00000000145665da>] kasan_populate_vmalloc+0x82/0x98
[ 553.332249] [<00000000144c88d0>] alloc_vmap_area+0x590/0x1c90
[ 553.332257] [<00000000144ca108>] __get_vm_area_node.constprop.0+0x138/0x260
[ 553.332265] [<00000000144d17fc>] __vmalloc_node_range+0x134/0x360
[ 553.332274] [<0000000013d5dbf2>] alloc_thread_stack_node+0x112/0x378
[ 553.332284] [<0000000013d62726>] dup_task_struct+0x66/0x430
[ 553.332293] [<0000000013d63962>] copy_process+0x432/0x4b80
[ 553.332302] [<0000000013d68300>] kernel_clone+0xf0/0x7d0
[ 553.332311] [<0000000013d68bd6>] __do_sys_clone+0xae/0xc8
[ 553.332400] [<0000000013d68dee>] __s390x_sys_clone+0xd6/0x118
[ 553.332410] [<0000000013c9d34c>] do_syscall+0x22c/0x328
[ 553.332419] [<00000000158e7366>] __do_syscall+0xce/0xf0
[ 553.332428] [<0000000015913260>] system_call+0x70/0x98
Instead of allocating single pages per-PTE, bulk-allocate the
shadow memory prior to applying kasan_populate_vmalloc_pte()
callback on a page range.
Suggested-by: Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc: stable@...r.kernel.org
Fixes: 3c5c3cfb9ef4 ("kasan: support backing vmalloc space with real shadow memory")
Signed-off-by: Alexander Gordeev <agordeev@...ux.ibm.com>
---
mm/kasan/shadow.c | 65 +++++++++++++++++++++++++++++++++++------------
1 file changed, 49 insertions(+), 16 deletions(-)
diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 88d1c9dcb507..ea9a06715a81 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -292,30 +292,65 @@ void __init __weak kasan_populate_early_vm_area_shadow(void *start,
{
}
+struct vmalloc_populate_data {
+ unsigned long start;
+ struct page **pages;
+};
+
static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
- void *unused)
+ void *_data)
{
- unsigned long page;
+ struct vmalloc_populate_data *data = _data;
+ struct page *page;
+ unsigned long pfn;
pte_t pte;
if (likely(!pte_none(ptep_get(ptep))))
return 0;
- page = __get_free_page(GFP_KERNEL);
- if (!page)
- return -ENOMEM;
-
- __memset((void *)page, KASAN_VMALLOC_INVALID, PAGE_SIZE);
- pte = pfn_pte(PFN_DOWN(__pa(page)), PAGE_KERNEL);
+ page = data->pages[PFN_DOWN(addr - data->start)];
+ pfn = page_to_pfn(page);
+ __memset(pfn_to_virt(pfn), KASAN_VMALLOC_INVALID, PAGE_SIZE);
+ pte = pfn_pte(pfn, PAGE_KERNEL);
spin_lock(&init_mm.page_table_lock);
- if (likely(pte_none(ptep_get(ptep)))) {
+ if (likely(pte_none(ptep_get(ptep))))
set_pte_at(&init_mm, addr, ptep, pte);
- page = 0;
- }
spin_unlock(&init_mm.page_table_lock);
- if (page)
- free_page(page);
+
+ return 0;
+}
+
+static int __kasan_populate_vmalloc(unsigned long start, unsigned long end)
+{
+ unsigned long nr_pages, nr_total = PFN_UP(end - start);
+ struct vmalloc_populate_data data;
+ int ret;
+
+ data.pages = (struct page **)__get_free_page(GFP_KERNEL);
+ if (!data.pages)
+ return -ENOMEM;
+
+ while (nr_total) {
+ nr_pages = min(nr_total, PAGE_SIZE / sizeof(data.pages[0]));
+ __memset(data.pages, 0, nr_pages * sizeof(data.pages[0]));
+ if (nr_pages != alloc_pages_bulk(GFP_KERNEL, nr_pages, data.pages)) {
+ free_page((unsigned long)data.pages);
+ return -ENOMEM;
+ }
+
+ data.start = start;
+ ret = apply_to_page_range(&init_mm, start, nr_pages * PAGE_SIZE,
+ kasan_populate_vmalloc_pte, &data);
+ if (ret)
+ return ret;
+
+ start += nr_pages * PAGE_SIZE;
+ nr_total -= nr_pages;
+ }
+
+ free_page((unsigned long)data.pages);
+
return 0;
}
@@ -348,9 +383,7 @@ int kasan_populate_vmalloc(unsigned long addr, unsigned long size)
shadow_start = PAGE_ALIGN_DOWN(shadow_start);
shadow_end = PAGE_ALIGN(shadow_end);
- ret = apply_to_page_range(&init_mm, shadow_start,
- shadow_end - shadow_start,
- kasan_populate_vmalloc_pte, NULL);
+ ret = __kasan_populate_vmalloc(shadow_start, shadow_end);
if (ret)
return ret;
--
2.45.2
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