[PATCH 1/2] kasan: fix crashes on access to memory mapped by vm_map_ram()

[PATCH 1/2] kasan: fix crashes on access to memory mapped by vm_map_ram()

[Andrey Ryabinin]

With CONFIG_KASAN_VMALLOC=y any use of memory obtained via vm_map_ram()
will crash because there is no shadow backing that memory.

Instead of sprinkling additional kasan_populate_vmalloc() calls all over
the vmalloc code, move it into alloc_vmap_area(). This will fix
vm_map_ram() and simplify the code a bit.

Fixes: 3c5c3cfb9ef4 ("kasan: support backing vmalloc space with real shadow memory")
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Reported-by: syzbot+82e323920b78d54aaed5@syzkaller.appspotmail.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
---
 include/linux/kasan.h | 15 +++++++++------
 mm/kasan/common.c     | 27 +++++++++++++++++---------
 mm/vmalloc.c          | 45 ++++++++++++++++++-------------------------
 3 files changed, 46 insertions(+), 41 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 4f404c565db1..e18fe54969e9 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -205,20 +205,23 @@ static inline void *kasan_reset_tag(const void *addr)
 #endif /* CONFIG_KASAN_SW_TAGS */
 
 #ifdef CONFIG_KASAN_VMALLOC
-int kasan_populate_vmalloc(unsigned long requested_size,
-			   struct vm_struct *area);
-void kasan_poison_vmalloc(void *start, unsigned long size);
+int kasan_populate_vmalloc(unsigned long addr, unsigned long size);
+void kasan_poison_vmalloc(const void *start, unsigned long size);
+void kasan_unpoison_vmalloc(const void *start, unsigned long size);
 void kasan_release_vmalloc(unsigned long start, unsigned long end,
 			   unsigned long free_region_start,
 			   unsigned long free_region_end);
 #else
-static inline int kasan_populate_vmalloc(unsigned long requested_size,
-					 struct vm_struct *area)
+static inline int kasan_populate_vmalloc(unsigned long start,
+					unsigned long size)
 {
 	return 0;
 }
 
-static inline void kasan_poison_vmalloc(void *start, unsigned long size) {}
+static inline void kasan_poison_vmalloc(const void *start, unsigned long size)
+{ }
+static inline void kasan_unpoison_vmalloc(const void *start, unsigned long size)
+{ }
 static inline void kasan_release_vmalloc(unsigned long start,
 					 unsigned long end,
 					 unsigned long free_region_start,
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index df3371d5c572..a1e6273be8c3 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -777,15 +777,17 @@ static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
 	return 0;
 }
 
-int kasan_populate_vmalloc(unsigned long requested_size, struct vm_struct *area)
+int kasan_populate_vmalloc(unsigned long addr, unsigned long size)
 {
 	unsigned long shadow_start, shadow_end;
 	int ret;
 
-	shadow_start = (unsigned long)kasan_mem_to_shadow(area->addr);
+	if (!is_vmalloc_or_module_addr((void *)addr))
+		return 0;
+
+	shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr);
 	shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
-	shadow_end = (unsigned long)kasan_mem_to_shadow(area->addr +
-							area->size);
+	shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size);
 	shadow_end = ALIGN(shadow_end, PAGE_SIZE);
 
 	ret = apply_to_page_range(&init_mm, shadow_start,
@@ -796,10 +798,6 @@ int kasan_populate_vmalloc(unsigned long requested_size, struct vm_struct *area)
 
 	flush_cache_vmap(shadow_start, shadow_end);
 
-	kasan_unpoison_shadow(area->addr, requested_size);
-
-	area->flags |= VM_KASAN;
-
 	/*
 	 * We need to be careful about inter-cpu effects here. Consider:
 	 *
@@ -842,12 +840,23 @@ int kasan_populate_vmalloc(unsigned long requested_size, struct vm_struct *area)
  * Poison the shadow for a vmalloc region. Called as part of the
  * freeing process at the time the region is freed.
  */
-void kasan_poison_vmalloc(void *start, unsigned long size)
+void kasan_poison_vmalloc(const void *start, unsigned long size)
 {
+	if (!is_vmalloc_or_module_addr(start))
+		return;
+
 	size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
 	kasan_poison_shadow(start, size, KASAN_VMALLOC_INVALID);
 }
 
+void kasan_unpoison_vmalloc(const void *start, unsigned long size)
+{
+	if (!is_vmalloc_or_module_addr(start))
+		return;
+
+	kasan_unpoison_shadow(start, size);
+}
+
 static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
 					void *unused)
 {
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 4d3b3d60d893..a5412f14f57f 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1073,6 +1073,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
 	struct vmap_area *va, *pva;
 	unsigned long addr;
 	int purged = 0;
+	int ret = -EBUSY;
 
 	BUG_ON(!size);
 	BUG_ON(offset_in_page(size));
@@ -1139,6 +1140,10 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
 	va->va_end = addr + size;
 	va->vm = NULL;
 
+	ret = kasan_populate_vmalloc(addr, size);
+	if (ret)
+		goto out;
+
 	spin_lock(&vmap_area_lock);
 	insert_vmap_area(va, &vmap_area_root, &vmap_area_list);
 	spin_unlock(&vmap_area_lock);
@@ -1169,8 +1174,9 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
 		pr_warn("vmap allocation for size %lu failed: use vmalloc=<size> to increase size\n",
 			size);
 
+out:
 	kmem_cache_free(vmap_area_cachep, va);
-	return ERR_PTR(-EBUSY);
+	return ERR_PTR(ret);
 }
 
 int register_vmap_purge_notifier(struct notifier_block *nb)
@@ -1771,6 +1777,8 @@ void vm_unmap_ram(const void *mem, unsigned int count)
 	BUG_ON(addr > VMALLOC_END);
 	BUG_ON(!PAGE_ALIGNED(addr));
 
+	kasan_poison_vmalloc(mem, size);
+
 	if (likely(count <= VMAP_MAX_ALLOC)) {
 		debug_check_no_locks_freed(mem, size);
 		vb_free(mem, size);
@@ -1821,6 +1829,9 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node, pgprot_t pro
 		addr = va->va_start;
 		mem = (void *)addr;
 	}
+
+	kasan_unpoison_vmalloc(mem, size);
+
 	if (vmap_page_range(addr, addr + size, prot, pages) < 0) {
 		vm_unmap_ram(mem, count);
 		return NULL;
@@ -2075,6 +2086,7 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
 {
 	struct vmap_area *va;
 	struct vm_struct *area;
+	unsigned long requested_size = size;
 
 	BUG_ON(in_interrupt());
 	size = PAGE_ALIGN(size);
@@ -2098,23 +2110,9 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
 		return NULL;
 	}
 
-	setup_vmalloc_vm(area, va, flags, caller);
+	kasan_unpoison_vmalloc((void *)va->va_start, requested_size);
 
-	/*
-	 * For KASAN, if we are in vmalloc space, we need to cover the shadow
-	 * area with real memory. If we come here through VM_ALLOC, this is
-	 * done by a higher level function that has access to the true size,
-	 * which might not be a full page.
-	 *
-	 * We assume module space comes via VM_ALLOC path.
-	 */
-	if (is_vmalloc_addr(area->addr) && !(area->flags & VM_ALLOC)) {
-		if (kasan_populate_vmalloc(area->size, area)) {
-			unmap_vmap_area(va);
-			kfree(area);
-			return NULL;
-		}
-	}
+	setup_vmalloc_vm(area, va, flags, caller);
 
 	return area;
 }
@@ -2293,8 +2291,7 @@ static void __vunmap(const void *addr, int deallocate_pages)
 	debug_check_no_locks_freed(area->addr, get_vm_area_size(area));
 	debug_check_no_obj_freed(area->addr, get_vm_area_size(area));
 
-	if (area->flags & VM_KASAN)
-		kasan_poison_vmalloc(area->addr, area->size);
+	kasan_poison_vmalloc(area->addr, area->size);
 
 	vm_remove_mappings(area, deallocate_pages);
 
@@ -2539,7 +2536,7 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 	if (!size || (size >> PAGE_SHIFT) > totalram_pages())
 		goto fail;
 
-	area = __get_vm_area_node(size, align, VM_ALLOC | VM_UNINITIALIZED |
+	area = __get_vm_area_node(real_size, align, VM_ALLOC | VM_UNINITIALIZED |
 				vm_flags, start, end, node, gfp_mask, caller);
 	if (!area)
 		goto fail;
@@ -2548,11 +2545,6 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 	if (!addr)
 		return NULL;
 
-	if (is_vmalloc_or_module_addr(area->addr)) {
-		if (kasan_populate_vmalloc(real_size, area))
-			return NULL;
-	}
-
 	/*
 	 * In this function, newly allocated vm_struct has VM_UNINITIALIZED
 	 * flag. It means that vm_struct is not fully initialized.
@@ -3437,7 +3429,8 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
 	/* populate the shadow space outside of the lock */
 	for (area = 0; area < nr_vms; area++) {
 		/* assume success here */
-		kasan_populate_vmalloc(sizes[area], vms[area]);
+		kasan_populate_vmalloc(vas[area]->va_start, sizes[area]);
+		kasan_unpoison_vmalloc((void *)vms[area]->addr, sizes[area]);
 	}
 
 	kfree(vas);
-- 
2.23.0

[PATCH 2/2] kasan: Don't allocate page tables in kasan_release_vmalloc()

[Andrey Ryabinin]

The purpose of kasan_release_vmalloc() is to unmap and deallocate shadow
memory. The usage of apply_to_page_range() isn't suitable in that scenario
because it allocates pages to fill missing page tables entries.
This also cause sleep in atomic bug:

	BUG: sleeping function called from invalid context at mm/page_alloc.c:4681
	in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 15087, name:

	Call Trace:
	 __dump_stack lib/dump_stack.c:77 [inline]
	 dump_stack+0x199/0x216 lib/dump_stack.c:118
	 ___might_sleep.cold.97+0x1f5/0x238 kernel/sched/core.c:6800
	 __might_sleep+0x95/0x190 kernel/sched/core.c:6753
	 prepare_alloc_pages mm/page_alloc.c:4681 [inline]
	 __alloc_pages_nodemask+0x3cd/0x890 mm/page_alloc.c:4730
	 alloc_pages_current+0x10c/0x210 mm/mempolicy.c:2211
	 alloc_pages include/linux/gfp.h:532 [inline]
	 __get_free_pages+0xc/0x40 mm/page_alloc.c:4786
	 __pte_alloc_one_kernel include/asm-generic/pgalloc.h:21 [inline]
	 pte_alloc_one_kernel include/asm-generic/pgalloc.h:33 [inline]
	 __pte_alloc_kernel+0x1d/0x200 mm/memory.c:459
	 apply_to_pte_range mm/memory.c:2031 [inline]
	 apply_to_pmd_range mm/memory.c:2068 [inline]
	 apply_to_pud_range mm/memory.c:2088 [inline]
	 apply_to_p4d_range mm/memory.c:2108 [inline]
	 apply_to_page_range+0x77d/0xa00 mm/memory.c:2133
	 kasan_release_vmalloc+0xa7/0xc0 mm/kasan/common.c:970
	 __purge_vmap_area_lazy+0xcbb/0x1f30 mm/vmalloc.c:1313
	 try_purge_vmap_area_lazy mm/vmalloc.c:1332 [inline]
	 free_vmap_area_noflush+0x2ca/0x390 mm/vmalloc.c:1368
	 free_unmap_vmap_area mm/vmalloc.c:1381 [inline]
	 remove_vm_area+0x1cc/0x230 mm/vmalloc.c:2209
	 vm_remove_mappings mm/vmalloc.c:2236 [inline]
	 __vunmap+0x223/0xa20 mm/vmalloc.c:2299
	 __vfree+0x3f/0xd0 mm/vmalloc.c:2356
	 __vmalloc_area_node mm/vmalloc.c:2507 [inline]
	 __vmalloc_node_range+0x5d5/0x810 mm/vmalloc.c:2547
	 __vmalloc_node mm/vmalloc.c:2607 [inline]
	 __vmalloc_node_flags mm/vmalloc.c:2621 [inline]
	 vzalloc+0x6f/0x80 mm/vmalloc.c:2666
	 alloc_one_pg_vec_page net/packet/af_packet.c:4233 [inline]
	 alloc_pg_vec net/packet/af_packet.c:4258 [inline]
	 packet_set_ring+0xbc0/0x1b50 net/packet/af_packet.c:4342
	 packet_setsockopt+0xed7/0x2d90 net/packet/af_packet.c:3695
	 __sys_setsockopt+0x29b/0x4d0 net/socket.c:2117
	 __do_sys_setsockopt net/socket.c:2133 [inline]
	 __se_sys_setsockopt net/socket.c:2130 [inline]
	 __x64_sys_setsockopt+0xbe/0x150 net/socket.c:2130
	 do_syscall_64+0xfa/0x780 arch/x86/entry/common.c:294
	 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Add kasan_unmap_page_range() which skips empty page table entries instead
of allocating them.

Fixes: 3c5c3cfb9ef4 ("kasan: support backing vmalloc space with real shadow memory")
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
---
 mm/kasan/common.c | 82 +++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 68 insertions(+), 14 deletions(-)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index a1e6273be8c3..e9ba7d8ad324 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -857,22 +857,77 @@ void kasan_unpoison_vmalloc(const void *start, unsigned long size)
 	kasan_unpoison_shadow(start, size);
 }
 
-static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
-					void *unused)
+static void kasan_unmap_pte_range(pmd_t *pmd, unsigned long addr,
+				unsigned long end)
 {
-	unsigned long page;
+	pte_t *pte;
 
-	page = (unsigned long)__va(pte_pfn(*ptep) << PAGE_SHIFT);
+	pte = pte_offset_kernel(pmd, addr);
+	do {
+		pte_t ptent = ptep_get_and_clear(&init_mm, addr, pte);
 
-	spin_lock(&init_mm.page_table_lock);
+		if (!pte_none(ptent))
+			__free_page(pte_page(ptent));
+	} while (pte++, addr += PAGE_SIZE, addr != end);
+}
 
-	if (likely(!pte_none(*ptep))) {
-		pte_clear(&init_mm, addr, ptep);
-		free_page(page);
-	}
-	spin_unlock(&init_mm.page_table_lock);
+static void kasan_unmap_pmd_range(pud_t *pud, unsigned long addr,
+				unsigned long end)
+{
+	pmd_t *pmd;
+	unsigned long next;
 
-	return 0;
+	pmd = pmd_offset(pud, addr);
+	do {
+		next = pmd_addr_end(addr, end);
+		if (pmd_none_or_clear_bad(pmd))
+			continue;
+		kasan_unmap_pte_range(pmd, addr, next);
+	} while (pmd++, addr = next, addr != end);
+}
+
+static void kasan_unmap_pud_range(p4d_t *p4d, unsigned long addr,
+				unsigned long end)
+{
+	pud_t *pud;
+	unsigned long next;
+
+	pud = pud_offset(p4d, addr);
+	do {
+		next = pud_addr_end(addr, end);
+		if (pud_none_or_clear_bad(pud))
+			continue;
+		kasan_unmap_pmd_range(pud, addr, next);
+	} while (pud++, addr = next, addr != end);
+}
+
+static void kasan_unmap_p4d_range(pgd_t *pgd, unsigned long addr,
+				unsigned long end)
+{
+	p4d_t *p4d;
+	unsigned long next;
+
+	p4d = p4d_offset(pgd, addr);
+	do {
+		next = p4d_addr_end(addr, end);
+		if (p4d_none_or_clear_bad(p4d))
+			continue;
+		kasan_unmap_pud_range(p4d, addr, next);
+	} while (p4d++, addr = next, addr != end);
+}
+
+static void kasan_unmap_page_range(unsigned long addr, unsigned long end)
+{
+	pgd_t *pgd;
+	unsigned long next;
+
+	pgd = pgd_offset_k(addr);
+	do {
+		next = pgd_addr_end(addr, end);
+		if (pgd_none_or_clear_bad(pgd))
+			continue;
+		kasan_unmap_p4d_range(pgd, addr, next);
+	} while (pgd++, addr = next, addr != end);
 }
 
 /*
@@ -978,9 +1033,8 @@ void kasan_release_vmalloc(unsigned long start, unsigned long end,
 	shadow_end = kasan_mem_to_shadow((void *)region_end);
 
 	if (shadow_end > shadow_start) {
-		apply_to_page_range(&init_mm, (unsigned long)shadow_start,
-				    (unsigned long)(shadow_end - shadow_start),
-				    kasan_depopulate_vmalloc_pte, NULL);
+		kasan_unmap_page_range((unsigned long)shadow_start,
+				    (unsigned long)shadow_end);
 		flush_tlb_kernel_range((unsigned long)shadow_start,
 				       (unsigned long)shadow_end);
 	}
-- 
2.23.0

Re: [PATCH 2/2] kasan: Don't allocate page tables in kasan_release_vmalloc()

[Andrew Morton]

On Wed,  4 Dec 2019 23:45:34 +0300 Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:

> The purpose of kasan_release_vmalloc() is to unmap and deallocate shadow
> memory. The usage of apply_to_page_range() isn't suitable in that scenario
> because it allocates pages to fill missing page tables entries.
> This also cause sleep in atomic bug:
> 
> 	BUG: sleeping function called from invalid context at mm/page_alloc.c:4681
> 	in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 15087, name:
> 
> 	Call Trace:
> 	 __dump_stack lib/dump_stack.c:77 [inline]
> 	 dump_stack+0x199/0x216 lib/dump_stack.c:118
> 	 ___might_sleep.cold.97+0x1f5/0x238 kernel/sched/core.c:6800
> 	 __might_sleep+0x95/0x190 kernel/sched/core.c:6753
> 	 prepare_alloc_pages mm/page_alloc.c:4681 [inline]
> 	 __alloc_pages_nodemask+0x3cd/0x890 mm/page_alloc.c:4730
> 	 alloc_pages_current+0x10c/0x210 mm/mempolicy.c:2211
> 	 alloc_pages include/linux/gfp.h:532 [inline]
> 	 __get_free_pages+0xc/0x40 mm/page_alloc.c:4786
> 	 __pte_alloc_one_kernel include/asm-generic/pgalloc.h:21 [inline]
> 	 pte_alloc_one_kernel include/asm-generic/pgalloc.h:33 [inline]
> 	 __pte_alloc_kernel+0x1d/0x200 mm/memory.c:459
> 	 apply_to_pte_range mm/memory.c:2031 [inline]
> 	 apply_to_pmd_range mm/memory.c:2068 [inline]
> 	 apply_to_pud_range mm/memory.c:2088 [inline]
> 	 apply_to_p4d_range mm/memory.c:2108 [inline]
> 	 apply_to_page_range+0x77d/0xa00 mm/memory.c:2133
> 	 kasan_release_vmalloc+0xa7/0xc0 mm/kasan/common.c:970
> 	 __purge_vmap_area_lazy+0xcbb/0x1f30 mm/vmalloc.c:1313
> 	 try_purge_vmap_area_lazy mm/vmalloc.c:1332 [inline]
> 	 free_vmap_area_noflush+0x2ca/0x390 mm/vmalloc.c:1368
> 	 free_unmap_vmap_area mm/vmalloc.c:1381 [inline]
> 	 remove_vm_area+0x1cc/0x230 mm/vmalloc.c:2209
> 	 vm_remove_mappings mm/vmalloc.c:2236 [inline]
> 	 __vunmap+0x223/0xa20 mm/vmalloc.c:2299
> 	 __vfree+0x3f/0xd0 mm/vmalloc.c:2356
> 	 __vmalloc_area_node mm/vmalloc.c:2507 [inline]
> 	 __vmalloc_node_range+0x5d5/0x810 mm/vmalloc.c:2547
> 	 __vmalloc_node mm/vmalloc.c:2607 [inline]
> 	 __vmalloc_node_flags mm/vmalloc.c:2621 [inline]
> 	 vzalloc+0x6f/0x80 mm/vmalloc.c:2666
> 	 alloc_one_pg_vec_page net/packet/af_packet.c:4233 [inline]
> 	 alloc_pg_vec net/packet/af_packet.c:4258 [inline]
> 	 packet_set_ring+0xbc0/0x1b50 net/packet/af_packet.c:4342
> 	 packet_setsockopt+0xed7/0x2d90 net/packet/af_packet.c:3695
> 	 __sys_setsockopt+0x29b/0x4d0 net/socket.c:2117
> 	 __do_sys_setsockopt net/socket.c:2133 [inline]
> 	 __se_sys_setsockopt net/socket.c:2130 [inline]
> 	 __x64_sys_setsockopt+0xbe/0x150 net/socket.c:2130
> 	 do_syscall_64+0xfa/0x780 arch/x86/entry/common.c:294
> 	 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Why is this warning happening?  Some lock held?  If so, which one?

> Add kasan_unmap_page_range() which skips empty page table entries instead
> of allocating them.

Adding an open-coded range walker is unfortunate.  Did you consider
generalizing apply_to_page_range() for this purpose?  I did - it looks
messy.

Somewhat.  I guess adding another arg to
apply_to_p4d_range...apply_to_pte_range wouldn't kill us.  I wonder if
there would be other sites which could utilize the additional control.

Re: [PATCH 1/2] kasan: fix crashes on access to memory mapped by vm_map_ram()

[Uladzislau Rezki]

> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 4d3b3d60d893..a5412f14f57f 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1073,6 +1073,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
>  	struct vmap_area *va, *pva;
>  	unsigned long addr;
>  	int purged = 0;
> +	int ret = -EBUSY;
>  
>  	BUG_ON(!size);
>  	BUG_ON(offset_in_page(size));
> @@ -1139,6 +1140,10 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
>  	va->va_end = addr + size;
>  	va->vm = NULL;
>  
> +	ret = kasan_populate_vmalloc(addr, size);
> +	if (ret)
> +		goto out;
> +
But it introduces another issues when is CONFIG_KASAN_VMALLOC=y. If
the kasan_populate_vmalloc() gets failed for some reason it just
leaves the function, that will lead to waste of vmap space.

>  	spin_lock(&vmap_area_lock);
>  	insert_vmap_area(va, &vmap_area_root, &vmap_area_list);
>  	spin_unlock(&vmap_area_lock);
>
     ret = kasan_populate_vmalloc(addr, size);
     if (ret) {
         free_vmap_area(va);
         return ERR_PTR(-EBUSY);;
     }

> @@ -1169,8 +1174,9 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
>  		pr_warn("vmap allocation for size %lu failed: use vmalloc=<size> to increase size\n",
>  			size);
>  
> +out:
>  	kmem_cache_free(vmap_area_cachep, va);
> -	return ERR_PTR(-EBUSY);
> +	return ERR_PTR(ret);
>  }
>  

Re: [PATCH 2/2] kasan: Don't allocate page tables in kasan_release_vmalloc()

[Daniel Axtens]

Andrey Ryabinin <aryabinin@virtuozzo.com> writes:

Ah you beat me by a few hours, I was going to send a similar but
slightly simpler patch - we should be able to use apply_to_page_range
for the 'inner' part of the range and just walk the page table for the
possible pages on the edges of the range. That means we could avoid a
full, loop-driven page table walker. But I'd also be very open to
generalising apply_to_page_range(); I think I'd add
apply_to_existing_pages() and add an argument to the static walker
functions.

Let me try that out and we'll see what it looks like.

Regards,
Daniel

> The purpose of kasan_release_vmalloc() is to unmap and deallocate shadow
> memory. The usage of apply_to_page_range() isn't suitable in that scenario
> because it allocates pages to fill missing page tables entries.
> This also cause sleep in atomic bug:
>
> 	BUG: sleeping function called from invalid context at mm/page_alloc.c:4681
> 	in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 15087, name:
>
> 	Call Trace:
> 	 __dump_stack lib/dump_stack.c:77 [inline]
> 	 dump_stack+0x199/0x216 lib/dump_stack.c:118
> 	 ___might_sleep.cold.97+0x1f5/0x238 kernel/sched/core.c:6800
> 	 __might_sleep+0x95/0x190 kernel/sched/core.c:6753
> 	 prepare_alloc_pages mm/page_alloc.c:4681 [inline]
> 	 __alloc_pages_nodemask+0x3cd/0x890 mm/page_alloc.c:4730
> 	 alloc_pages_current+0x10c/0x210 mm/mempolicy.c:2211
> 	 alloc_pages include/linux/gfp.h:532 [inline]
> 	 __get_free_pages+0xc/0x40 mm/page_alloc.c:4786
> 	 __pte_alloc_one_kernel include/asm-generic/pgalloc.h:21 [inline]
> 	 pte_alloc_one_kernel include/asm-generic/pgalloc.h:33 [inline]
> 	 __pte_alloc_kernel+0x1d/0x200 mm/memory.c:459
> 	 apply_to_pte_range mm/memory.c:2031 [inline]
> 	 apply_to_pmd_range mm/memory.c:2068 [inline]
> 	 apply_to_pud_range mm/memory.c:2088 [inline]
> 	 apply_to_p4d_range mm/memory.c:2108 [inline]
> 	 apply_to_page_range+0x77d/0xa00 mm/memory.c:2133
> 	 kasan_release_vmalloc+0xa7/0xc0 mm/kasan/common.c:970
> 	 __purge_vmap_area_lazy+0xcbb/0x1f30 mm/vmalloc.c:1313
> 	 try_purge_vmap_area_lazy mm/vmalloc.c:1332 [inline]
> 	 free_vmap_area_noflush+0x2ca/0x390 mm/vmalloc.c:1368
> 	 free_unmap_vmap_area mm/vmalloc.c:1381 [inline]
> 	 remove_vm_area+0x1cc/0x230 mm/vmalloc.c:2209
> 	 vm_remove_mappings mm/vmalloc.c:2236 [inline]
> 	 __vunmap+0x223/0xa20 mm/vmalloc.c:2299
> 	 __vfree+0x3f/0xd0 mm/vmalloc.c:2356
> 	 __vmalloc_area_node mm/vmalloc.c:2507 [inline]
> 	 __vmalloc_node_range+0x5d5/0x810 mm/vmalloc.c:2547
> 	 __vmalloc_node mm/vmalloc.c:2607 [inline]
> 	 __vmalloc_node_flags mm/vmalloc.c:2621 [inline]
> 	 vzalloc+0x6f/0x80 mm/vmalloc.c:2666
> 	 alloc_one_pg_vec_page net/packet/af_packet.c:4233 [inline]
> 	 alloc_pg_vec net/packet/af_packet.c:4258 [inline]
> 	 packet_set_ring+0xbc0/0x1b50 net/packet/af_packet.c:4342
> 	 packet_setsockopt+0xed7/0x2d90 net/packet/af_packet.c:3695
> 	 __sys_setsockopt+0x29b/0x4d0 net/socket.c:2117
> 	 __do_sys_setsockopt net/socket.c:2133 [inline]
> 	 __se_sys_setsockopt net/socket.c:2130 [inline]
> 	 __x64_sys_setsockopt+0xbe/0x150 net/socket.c:2130
> 	 do_syscall_64+0xfa/0x780 arch/x86/entry/common.c:294
> 	 entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Add kasan_unmap_page_range() which skips empty page table entries instead
> of allocating them.
>
> Fixes: 3c5c3cfb9ef4 ("kasan: support backing vmalloc space with real shadow memory")
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> ---
>  mm/kasan/common.c | 82 +++++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 68 insertions(+), 14 deletions(-)
>
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index a1e6273be8c3..e9ba7d8ad324 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -857,22 +857,77 @@ void kasan_unpoison_vmalloc(const void *start, unsigned long size)
>  	kasan_unpoison_shadow(start, size);
>  }
>  
> -static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
> -					void *unused)
> +static void kasan_unmap_pte_range(pmd_t *pmd, unsigned long addr,
> +				unsigned long end)
>  {
> -	unsigned long page;
> +	pte_t *pte;
>  
> -	page = (unsigned long)__va(pte_pfn(*ptep) << PAGE_SHIFT);
> +	pte = pte_offset_kernel(pmd, addr);
> +	do {
> +		pte_t ptent = ptep_get_and_clear(&init_mm, addr, pte);
>  
> -	spin_lock(&init_mm.page_table_lock);
> +		if (!pte_none(ptent))
> +			__free_page(pte_page(ptent));
> +	} while (pte++, addr += PAGE_SIZE, addr != end);
> +}
>  
> -	if (likely(!pte_none(*ptep))) {
> -		pte_clear(&init_mm, addr, ptep);
> -		free_page(page);
> -	}
> -	spin_unlock(&init_mm.page_table_lock);
> +static void kasan_unmap_pmd_range(pud_t *pud, unsigned long addr,
> +				unsigned long end)
> +{
> +	pmd_t *pmd;
> +	unsigned long next;
>  
> -	return 0;
> +	pmd = pmd_offset(pud, addr);
> +	do {
> +		next = pmd_addr_end(addr, end);
> +		if (pmd_none_or_clear_bad(pmd))
> +			continue;
> +		kasan_unmap_pte_range(pmd, addr, next);
> +	} while (pmd++, addr = next, addr != end);
> +}
> +
> +static void kasan_unmap_pud_range(p4d_t *p4d, unsigned long addr,
> +				unsigned long end)
> +{
> +	pud_t *pud;
> +	unsigned long next;
> +
> +	pud = pud_offset(p4d, addr);
> +	do {
> +		next = pud_addr_end(addr, end);
> +		if (pud_none_or_clear_bad(pud))
> +			continue;
> +		kasan_unmap_pmd_range(pud, addr, next);
> +	} while (pud++, addr = next, addr != end);
> +}
> +
> +static void kasan_unmap_p4d_range(pgd_t *pgd, unsigned long addr,
> +				unsigned long end)
> +{
> +	p4d_t *p4d;
> +	unsigned long next;
> +
> +	p4d = p4d_offset(pgd, addr);
> +	do {
> +		next = p4d_addr_end(addr, end);
> +		if (p4d_none_or_clear_bad(p4d))
> +			continue;
> +		kasan_unmap_pud_range(p4d, addr, next);
> +	} while (p4d++, addr = next, addr != end);
> +}
> +
> +static void kasan_unmap_page_range(unsigned long addr, unsigned long end)
> +{
> +	pgd_t *pgd;
> +	unsigned long next;
> +
> +	pgd = pgd_offset_k(addr);
> +	do {
> +		next = pgd_addr_end(addr, end);
> +		if (pgd_none_or_clear_bad(pgd))
> +			continue;
> +		kasan_unmap_p4d_range(pgd, addr, next);
> +	} while (pgd++, addr = next, addr != end);
>  }
>  
>  /*
> @@ -978,9 +1033,8 @@ void kasan_release_vmalloc(unsigned long start, unsigned long end,
>  	shadow_end = kasan_mem_to_shadow((void *)region_end);
>  
>  	if (shadow_end > shadow_start) {
> -		apply_to_page_range(&init_mm, (unsigned long)shadow_start,
> -				    (unsigned long)(shadow_end - shadow_start),
> -				    kasan_depopulate_vmalloc_pte, NULL);
> +		kasan_unmap_page_range((unsigned long)shadow_start,
> +				    (unsigned long)shadow_end);
>  		flush_tlb_kernel_range((unsigned long)shadow_start,
>  				       (unsigned long)shadow_end);
>  	}
> -- 
> 2.23.0

[PATCH v2] kasan: fix crashes on access to memory mapped by vm_map_ram()

[Andrey Ryabinin]

With CONFIG_KASAN_VMALLOC=y any use of memory obtained via vm_map_ram()
will crash because there is no shadow backing that memory.

Instead of sprinkling additional kasan_populate_vmalloc() calls all over
the vmalloc code, move it into alloc_vmap_area(). This will fix
vm_map_ram() and simplify the code a bit.

Fixes: 3c5c3cfb9ef4 ("kasan: support backing vmalloc space with real shadow memory")
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
---

 Changes since v1:
  - Fix error path in alloc_vmap_area.
  - Remove wrong Reported-by: syzbot (The issue reported by bot is a different one)

 include/linux/kasan.h | 15 +++++---
 mm/kasan/common.c     | 27 +++++++++-----
 mm/vmalloc.c          | 85 ++++++++++++++++++++-----------------------
 3 files changed, 67 insertions(+), 60 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 4f404c565db1..e18fe54969e9 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -205,20 +205,23 @@ static inline void *kasan_reset_tag(const void *addr)
 #endif /* CONFIG_KASAN_SW_TAGS */
 
 #ifdef CONFIG_KASAN_VMALLOC
-int kasan_populate_vmalloc(unsigned long requested_size,
-			   struct vm_struct *area);
-void kasan_poison_vmalloc(void *start, unsigned long size);
+int kasan_populate_vmalloc(unsigned long addr, unsigned long size);
+void kasan_poison_vmalloc(const void *start, unsigned long size);
+void kasan_unpoison_vmalloc(const void *start, unsigned long size);
 void kasan_release_vmalloc(unsigned long start, unsigned long end,
 			   unsigned long free_region_start,
 			   unsigned long free_region_end);
 #else
-static inline int kasan_populate_vmalloc(unsigned long requested_size,
-					 struct vm_struct *area)
+static inline int kasan_populate_vmalloc(unsigned long start,
+					unsigned long size)
 {
 	return 0;
 }
 
-static inline void kasan_poison_vmalloc(void *start, unsigned long size) {}
+static inline void kasan_poison_vmalloc(const void *start, unsigned long size)
+{ }
+static inline void kasan_unpoison_vmalloc(const void *start, unsigned long size)
+{ }
 static inline void kasan_release_vmalloc(unsigned long start,
 					 unsigned long end,
 					 unsigned long free_region_start,
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index df3371d5c572..a1e6273be8c3 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -777,15 +777,17 @@ static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
 	return 0;
 }
 
-int kasan_populate_vmalloc(unsigned long requested_size, struct vm_struct *area)
+int kasan_populate_vmalloc(unsigned long addr, unsigned long size)
 {
 	unsigned long shadow_start, shadow_end;
 	int ret;
 
-	shadow_start = (unsigned long)kasan_mem_to_shadow(area->addr);
+	if (!is_vmalloc_or_module_addr((void *)addr))
+		return 0;
+
+	shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr);
 	shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
-	shadow_end = (unsigned long)kasan_mem_to_shadow(area->addr +
-							area->size);
+	shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size);
 	shadow_end = ALIGN(shadow_end, PAGE_SIZE);
 
 	ret = apply_to_page_range(&init_mm, shadow_start,
@@ -796,10 +798,6 @@ int kasan_populate_vmalloc(unsigned long requested_size, struct vm_struct *area)
 
 	flush_cache_vmap(shadow_start, shadow_end);
 
-	kasan_unpoison_shadow(area->addr, requested_size);
-
-	area->flags |= VM_KASAN;
-
 	/*
 	 * We need to be careful about inter-cpu effects here. Consider:
 	 *
@@ -842,12 +840,23 @@ int kasan_populate_vmalloc(unsigned long requested_size, struct vm_struct *area)
  * Poison the shadow for a vmalloc region. Called as part of the
  * freeing process at the time the region is freed.
  */
-void kasan_poison_vmalloc(void *start, unsigned long size)
+void kasan_poison_vmalloc(const void *start, unsigned long size)
 {
+	if (!is_vmalloc_or_module_addr(start))
+		return;
+
 	size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
 	kasan_poison_shadow(start, size, KASAN_VMALLOC_INVALID);
 }
 
+void kasan_unpoison_vmalloc(const void *start, unsigned long size)
+{
+	if (!is_vmalloc_or_module_addr(start))
+		return;
+
+	kasan_unpoison_shadow(start, size);
+}
+
 static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
 					void *unused)
 {
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 4d3b3d60d893..6e865cea846c 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1061,6 +1061,26 @@ __alloc_vmap_area(unsigned long size, unsigned long align,
 	return nva_start_addr;
 }
 
+/*
+ * Free a region of KVA allocated by alloc_vmap_area
+ */
+static void free_vmap_area(struct vmap_area *va)
+{
+	/*
+	 * Remove from the busy tree/list.
+	 */
+	spin_lock(&vmap_area_lock);
+	unlink_va(va, &vmap_area_root);
+	spin_unlock(&vmap_area_lock);
+
+	/*
+	 * Insert/Merge it back to the free tree/list.
+	 */
+	spin_lock(&free_vmap_area_lock);
+	merge_or_add_vmap_area(va, &free_vmap_area_root, &free_vmap_area_list);
+	spin_unlock(&free_vmap_area_lock);
+}
+
 /*
  * Allocate a region of KVA of the specified size and alignment, within the
  * vstart and vend.
@@ -1073,6 +1093,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
 	struct vmap_area *va, *pva;
 	unsigned long addr;
 	int purged = 0;
+	int ret;
 
 	BUG_ON(!size);
 	BUG_ON(offset_in_page(size));
@@ -1139,6 +1160,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
 	va->va_end = addr + size;
 	va->vm = NULL;
 
+
 	spin_lock(&vmap_area_lock);
 	insert_vmap_area(va, &vmap_area_root, &vmap_area_list);
 	spin_unlock(&vmap_area_lock);
@@ -1147,6 +1169,12 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
 	BUG_ON(va->va_start < vstart);
 	BUG_ON(va->va_end > vend);
 
+	ret = kasan_populate_vmalloc(addr, size);
+	if (ret) {
+		free_vmap_area(va);
+		return ERR_PTR(ret);
+	}
+
 	return va;
 
 overflow:
@@ -1185,26 +1213,6 @@ int unregister_vmap_purge_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL_GPL(unregister_vmap_purge_notifier);
 
-/*
- * Free a region of KVA allocated by alloc_vmap_area
- */
-static void free_vmap_area(struct vmap_area *va)
-{
-	/*
-	 * Remove from the busy tree/list.
-	 */
-	spin_lock(&vmap_area_lock);
-	unlink_va(va, &vmap_area_root);
-	spin_unlock(&vmap_area_lock);
-
-	/*
-	 * Insert/Merge it back to the free tree/list.
-	 */
-	spin_lock(&free_vmap_area_lock);
-	merge_or_add_vmap_area(va, &free_vmap_area_root, &free_vmap_area_list);
-	spin_unlock(&free_vmap_area_lock);
-}
-
 /*
  * Clear the pagetable entries of a given vmap_area
  */
@@ -1771,6 +1779,8 @@ void vm_unmap_ram(const void *mem, unsigned int count)
 	BUG_ON(addr > VMALLOC_END);
 	BUG_ON(!PAGE_ALIGNED(addr));
 
+	kasan_poison_vmalloc(mem, size);
+
 	if (likely(count <= VMAP_MAX_ALLOC)) {
 		debug_check_no_locks_freed(mem, size);
 		vb_free(mem, size);
@@ -1821,6 +1831,9 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node, pgprot_t pro
 		addr = va->va_start;
 		mem = (void *)addr;
 	}
+
+	kasan_unpoison_vmalloc(mem, size);
+
 	if (vmap_page_range(addr, addr + size, prot, pages) < 0) {
 		vm_unmap_ram(mem, count);
 		return NULL;
@@ -2075,6 +2088,7 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
 {
 	struct vmap_area *va;
 	struct vm_struct *area;
+	unsigned long requested_size = size;
 
 	BUG_ON(in_interrupt());
 	size = PAGE_ALIGN(size);
@@ -2098,23 +2112,9 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
 		return NULL;
 	}
 
-	setup_vmalloc_vm(area, va, flags, caller);
+	kasan_unpoison_vmalloc((void *)va->va_start, requested_size);
 
-	/*
-	 * For KASAN, if we are in vmalloc space, we need to cover the shadow
-	 * area with real memory. If we come here through VM_ALLOC, this is
-	 * done by a higher level function that has access to the true size,
-	 * which might not be a full page.
-	 *
-	 * We assume module space comes via VM_ALLOC path.
-	 */
-	if (is_vmalloc_addr(area->addr) && !(area->flags & VM_ALLOC)) {
-		if (kasan_populate_vmalloc(area->size, area)) {
-			unmap_vmap_area(va);
-			kfree(area);
-			return NULL;
-		}
-	}
+	setup_vmalloc_vm(area, va, flags, caller);
 
 	return area;
 }
@@ -2293,8 +2293,7 @@ static void __vunmap(const void *addr, int deallocate_pages)
 	debug_check_no_locks_freed(area->addr, get_vm_area_size(area));
 	debug_check_no_obj_freed(area->addr, get_vm_area_size(area));
 
-	if (area->flags & VM_KASAN)
-		kasan_poison_vmalloc(area->addr, area->size);
+	kasan_poison_vmalloc(area->addr, area->size);
 
 	vm_remove_mappings(area, deallocate_pages);
 
@@ -2539,7 +2538,7 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 	if (!size || (size >> PAGE_SHIFT) > totalram_pages())
 		goto fail;
 
-	area = __get_vm_area_node(size, align, VM_ALLOC | VM_UNINITIALIZED |
+	area = __get_vm_area_node(real_size, align, VM_ALLOC | VM_UNINITIALIZED |
 				vm_flags, start, end, node, gfp_mask, caller);
 	if (!area)
 		goto fail;
@@ -2548,11 +2547,6 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 	if (!addr)
 		return NULL;
 
-	if (is_vmalloc_or_module_addr(area->addr)) {
-		if (kasan_populate_vmalloc(real_size, area))
-			return NULL;
-	}
-
 	/*
 	 * In this function, newly allocated vm_struct has VM_UNINITIALIZED
 	 * flag. It means that vm_struct is not fully initialized.
@@ -3437,7 +3431,8 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
 	/* populate the shadow space outside of the lock */
 	for (area = 0; area < nr_vms; area++) {
 		/* assume success here */
-		kasan_populate_vmalloc(sizes[area], vms[area]);
+		kasan_populate_vmalloc(vas[area]->va_start, sizes[area]);
+		kasan_unpoison_vmalloc((void *)vms[area]->addr, sizes[area]);
 	}
 
 	kfree(vas);
-- 
2.23.0

Re: [PATCH 2/2] kasan: Don't allocate page tables in kasan_release_vmalloc()

[Daniel Axtens]

Daniel Axtens <dja@axtens.net> writes:

> Andrey Ryabinin <aryabinin@virtuozzo.com> writes:
>
> Ah you beat me by a few hours, I was going to send a similar but
> slightly simpler patch - we should be able to use apply_to_page_range
> for the 'inner' part of the range and just walk the page table for the
> possible pages on the edges of the range. That means we could avoid a
> full, loop-driven page table walker. But I'd also be very open to
> generalising apply_to_page_range(); I think I'd add
> apply_to_existing_pages() and add an argument to the static walker
> functions.
>
> Let me try that out and we'll see what it looks like.

I had a go, it's here:

https://lore.kernel.org/linux-mm/20191205140407.1874-1-dja@axtens.net/T/#t

I think it's ugly but not so ugly as to not be worth it. There's also
another patch for syzkaller bugs that Dmitry picked up as patch 3 of the
series, it works and is needed whether you want to go with my approach
or Andrey's.

Regards,
Daniel

>
> Regards,
> Daniel
>
>> The purpose of kasan_release_vmalloc() is to unmap and deallocate shadow
>> memory. The usage of apply_to_page_range() isn't suitable in that scenario
>> because it allocates pages to fill missing page tables entries.
>> This also cause sleep in atomic bug:
>>
>> 	BUG: sleeping function called from invalid context at mm/page_alloc.c:4681
>> 	in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 15087, name:
>>
>> 	Call Trace:
>> 	 __dump_stack lib/dump_stack.c:77 [inline]
>> 	 dump_stack+0x199/0x216 lib/dump_stack.c:118
>> 	 ___might_sleep.cold.97+0x1f5/0x238 kernel/sched/core.c:6800
>> 	 __might_sleep+0x95/0x190 kernel/sched/core.c:6753
>> 	 prepare_alloc_pages mm/page_alloc.c:4681 [inline]
>> 	 __alloc_pages_nodemask+0x3cd/0x890 mm/page_alloc.c:4730
>> 	 alloc_pages_current+0x10c/0x210 mm/mempolicy.c:2211
>> 	 alloc_pages include/linux/gfp.h:532 [inline]
>> 	 __get_free_pages+0xc/0x40 mm/page_alloc.c:4786
>> 	 __pte_alloc_one_kernel include/asm-generic/pgalloc.h:21 [inline]
>> 	 pte_alloc_one_kernel include/asm-generic/pgalloc.h:33 [inline]
>> 	 __pte_alloc_kernel+0x1d/0x200 mm/memory.c:459
>> 	 apply_to_pte_range mm/memory.c:2031 [inline]
>> 	 apply_to_pmd_range mm/memory.c:2068 [inline]
>> 	 apply_to_pud_range mm/memory.c:2088 [inline]
>> 	 apply_to_p4d_range mm/memory.c:2108 [inline]
>> 	 apply_to_page_range+0x77d/0xa00 mm/memory.c:2133
>> 	 kasan_release_vmalloc+0xa7/0xc0 mm/kasan/common.c:970
>> 	 __purge_vmap_area_lazy+0xcbb/0x1f30 mm/vmalloc.c:1313
>> 	 try_purge_vmap_area_lazy mm/vmalloc.c:1332 [inline]
>> 	 free_vmap_area_noflush+0x2ca/0x390 mm/vmalloc.c:1368
>> 	 free_unmap_vmap_area mm/vmalloc.c:1381 [inline]
>> 	 remove_vm_area+0x1cc/0x230 mm/vmalloc.c:2209
>> 	 vm_remove_mappings mm/vmalloc.c:2236 [inline]
>> 	 __vunmap+0x223/0xa20 mm/vmalloc.c:2299
>> 	 __vfree+0x3f/0xd0 mm/vmalloc.c:2356
>> 	 __vmalloc_area_node mm/vmalloc.c:2507 [inline]
>> 	 __vmalloc_node_range+0x5d5/0x810 mm/vmalloc.c:2547
>> 	 __vmalloc_node mm/vmalloc.c:2607 [inline]
>> 	 __vmalloc_node_flags mm/vmalloc.c:2621 [inline]
>> 	 vzalloc+0x6f/0x80 mm/vmalloc.c:2666
>> 	 alloc_one_pg_vec_page net/packet/af_packet.c:4233 [inline]
>> 	 alloc_pg_vec net/packet/af_packet.c:4258 [inline]
>> 	 packet_set_ring+0xbc0/0x1b50 net/packet/af_packet.c:4342
>> 	 packet_setsockopt+0xed7/0x2d90 net/packet/af_packet.c:3695
>> 	 __sys_setsockopt+0x29b/0x4d0 net/socket.c:2117
>> 	 __do_sys_setsockopt net/socket.c:2133 [inline]
>> 	 __se_sys_setsockopt net/socket.c:2130 [inline]
>> 	 __x64_sys_setsockopt+0xbe/0x150 net/socket.c:2130
>> 	 do_syscall_64+0xfa/0x780 arch/x86/entry/common.c:294
>> 	 entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>
>> Add kasan_unmap_page_range() which skips empty page table entries instead
>> of allocating them.
>>
>> Fixes: 3c5c3cfb9ef4 ("kasan: support backing vmalloc space with real shadow memory")
>> Reported-by: Dmitry Vyukov <dvyukov@google.com>
>> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
>> ---
>>  mm/kasan/common.c | 82 +++++++++++++++++++++++++++++++++++++++--------
>>  1 file changed, 68 insertions(+), 14 deletions(-)
>>
>> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
>> index a1e6273be8c3..e9ba7d8ad324 100644
>> --- a/mm/kasan/common.c
>> +++ b/mm/kasan/common.c
>> @@ -857,22 +857,77 @@ void kasan_unpoison_vmalloc(const void *start, unsigned long size)
>>  	kasan_unpoison_shadow(start, size);
>>  }
>>  
>> -static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
>> -					void *unused)
>> +static void kasan_unmap_pte_range(pmd_t *pmd, unsigned long addr,
>> +				unsigned long end)
>>  {
>> -	unsigned long page;
>> +	pte_t *pte;
>>  
>> -	page = (unsigned long)__va(pte_pfn(*ptep) << PAGE_SHIFT);
>> +	pte = pte_offset_kernel(pmd, addr);
>> +	do {
>> +		pte_t ptent = ptep_get_and_clear(&init_mm, addr, pte);
>>  
>> -	spin_lock(&init_mm.page_table_lock);
>> +		if (!pte_none(ptent))
>> +			__free_page(pte_page(ptent));
>> +	} while (pte++, addr += PAGE_SIZE, addr != end);
>> +}
>>  
>> -	if (likely(!pte_none(*ptep))) {
>> -		pte_clear(&init_mm, addr, ptep);
>> -		free_page(page);
>> -	}
>> -	spin_unlock(&init_mm.page_table_lock);
>> +static void kasan_unmap_pmd_range(pud_t *pud, unsigned long addr,
>> +				unsigned long end)
>> +{
>> +	pmd_t *pmd;
>> +	unsigned long next;
>>  
>> -	return 0;
>> +	pmd = pmd_offset(pud, addr);
>> +	do {
>> +		next = pmd_addr_end(addr, end);
>> +		if (pmd_none_or_clear_bad(pmd))
>> +			continue;
>> +		kasan_unmap_pte_range(pmd, addr, next);
>> +	} while (pmd++, addr = next, addr != end);
>> +}
>> +
>> +static void kasan_unmap_pud_range(p4d_t *p4d, unsigned long addr,
>> +				unsigned long end)
>> +{
>> +	pud_t *pud;
>> +	unsigned long next;
>> +
>> +	pud = pud_offset(p4d, addr);
>> +	do {
>> +		next = pud_addr_end(addr, end);
>> +		if (pud_none_or_clear_bad(pud))
>> +			continue;
>> +		kasan_unmap_pmd_range(pud, addr, next);
>> +	} while (pud++, addr = next, addr != end);
>> +}
>> +
>> +static void kasan_unmap_p4d_range(pgd_t *pgd, unsigned long addr,
>> +				unsigned long end)
>> +{
>> +	p4d_t *p4d;
>> +	unsigned long next;
>> +
>> +	p4d = p4d_offset(pgd, addr);
>> +	do {
>> +		next = p4d_addr_end(addr, end);
>> +		if (p4d_none_or_clear_bad(p4d))
>> +			continue;
>> +		kasan_unmap_pud_range(p4d, addr, next);
>> +	} while (p4d++, addr = next, addr != end);
>> +}
>> +
>> +static void kasan_unmap_page_range(unsigned long addr, unsigned long end)
>> +{
>> +	pgd_t *pgd;
>> +	unsigned long next;
>> +
>> +	pgd = pgd_offset_k(addr);
>> +	do {
>> +		next = pgd_addr_end(addr, end);
>> +		if (pgd_none_or_clear_bad(pgd))
>> +			continue;
>> +		kasan_unmap_p4d_range(pgd, addr, next);
>> +	} while (pgd++, addr = next, addr != end);
>>  }
>>  
>>  /*
>> @@ -978,9 +1033,8 @@ void kasan_release_vmalloc(unsigned long start, unsigned long end,
>>  	shadow_end = kasan_mem_to_shadow((void *)region_end);
>>  
>>  	if (shadow_end > shadow_start) {
>> -		apply_to_page_range(&init_mm, (unsigned long)shadow_start,
>> -				    (unsigned long)(shadow_end - shadow_start),
>> -				    kasan_depopulate_vmalloc_pte, NULL);
>> +		kasan_unmap_page_range((unsigned long)shadow_start,
>> +				    (unsigned long)shadow_end);
>>  		flush_tlb_kernel_range((unsigned long)shadow_start,
>>  				       (unsigned long)shadow_end);
>>  	}
>> -- 
>> 2.23.0

Re: [PATCH 2/2] kasan: Don't allocate page tables in kasan_release_vmalloc()

[Andrey Ryabinin]

On 12/5/19 1:22 AM, Andrew Morton wrote:
> On Wed,  4 Dec 2019 23:45:34 +0300 Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:
> 
>> The purpose of kasan_release_vmalloc() is to unmap and deallocate shadow
>> memory. The usage of apply_to_page_range() isn't suitable in that scenario
>> because it allocates pages to fill missing page tables entries.
>> This also cause sleep in atomic bug:
>>
>> 	BUG: sleeping function called from invalid context at mm/page_alloc.c:4681
>> 	in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 15087, name:
>>
>> 	Call Trace:
>> 	 __dump_stack lib/dump_stack.c:77 [inline]
>> 	 dump_stack+0x199/0x216 lib/dump_stack.c:118
>> 	 ___might_sleep.cold.97+0x1f5/0x238 kernel/sched/core.c:6800
>> 	 __might_sleep+0x95/0x190 kernel/sched/core.c:6753
>> 	 prepare_alloc_pages mm/page_alloc.c:4681 [inline]
>> 	 __alloc_pages_nodemask+0x3cd/0x890 mm/page_alloc.c:4730
>> 	 alloc_pages_current+0x10c/0x210 mm/mempolicy.c:2211
>> 	 alloc_pages include/linux/gfp.h:532 [inline]
>> 	 __get_free_pages+0xc/0x40 mm/page_alloc.c:4786
>> 	 __pte_alloc_one_kernel include/asm-generic/pgalloc.h:21 [inline]
>> 	 pte_alloc_one_kernel include/asm-generic/pgalloc.h:33 [inline]
>> 	 __pte_alloc_kernel+0x1d/0x200 mm/memory.c:459
>> 	 apply_to_pte_range mm/memory.c:2031 [inline]
>> 	 apply_to_pmd_range mm/memory.c:2068 [inline]
>> 	 apply_to_pud_range mm/memory.c:2088 [inline]
>> 	 apply_to_p4d_range mm/memory.c:2108 [inline]
>> 	 apply_to_page_range+0x77d/0xa00 mm/memory.c:2133
>> 	 kasan_release_vmalloc+0xa7/0xc0 mm/kasan/common.c:970
>> 	 __purge_vmap_area_lazy+0xcbb/0x1f30 mm/vmalloc.c:1313
>> 	 try_purge_vmap_area_lazy mm/vmalloc.c:1332 [inline]
>> 	 free_vmap_area_noflush+0x2ca/0x390 mm/vmalloc.c:1368
>> 	 free_unmap_vmap_area mm/vmalloc.c:1381 [inline]
>> 	 remove_vm_area+0x1cc/0x230 mm/vmalloc.c:2209
>> 	 vm_remove_mappings mm/vmalloc.c:2236 [inline]
>> 	 __vunmap+0x223/0xa20 mm/vmalloc.c:2299
>> 	 __vfree+0x3f/0xd0 mm/vmalloc.c:2356
>> 	 __vmalloc_area_node mm/vmalloc.c:2507 [inline]
>> 	 __vmalloc_node_range+0x5d5/0x810 mm/vmalloc.c:2547
>> 	 __vmalloc_node mm/vmalloc.c:2607 [inline]
>> 	 __vmalloc_node_flags mm/vmalloc.c:2621 [inline]
>> 	 vzalloc+0x6f/0x80 mm/vmalloc.c:2666
>> 	 alloc_one_pg_vec_page net/packet/af_packet.c:4233 [inline]
>> 	 alloc_pg_vec net/packet/af_packet.c:4258 [inline]
>> 	 packet_set_ring+0xbc0/0x1b50 net/packet/af_packet.c:4342
>> 	 packet_setsockopt+0xed7/0x2d90 net/packet/af_packet.c:3695
>> 	 __sys_setsockopt+0x29b/0x4d0 net/socket.c:2117
>> 	 __do_sys_setsockopt net/socket.c:2133 [inline]
>> 	 __se_sys_setsockopt net/socket.c:2130 [inline]
>> 	 __x64_sys_setsockopt+0xbe/0x150 net/socket.c:2130
>> 	 do_syscall_64+0xfa/0x780 arch/x86/entry/common.c:294
>> 	 entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> Why is this warning happening?  Some lock held?  If so, which one?

spin_lock(&free_vmap_area_lock);

> 
>> Add kasan_unmap_page_range() which skips empty page table entries instead
>> of allocating them.
> 
> Adding an open-coded range walker is unfortunate.  Did you consider
> generalizing apply_to_page_range() for this purpose?  I did - it looks
> messy.
> 
> Somewhat.  I guess adding another arg to
> apply_to_p4d_range...apply_to_pte_range wouldn't kill us.  I wonder if
> there would be other sites which could utilize the additional control.
> 
> 

Re: [PATCH v2] kasan: fix crashes on access to memory mapped by vm_map_ram()

[Uladzislau Rezki]

On Thu, Dec 05, 2019 at 12:59:42PM +0300, Andrey Ryabinin wrote:
> With CONFIG_KASAN_VMALLOC=y any use of memory obtained via vm_map_ram()
> will crash because there is no shadow backing that memory.
> 
> Instead of sprinkling additional kasan_populate_vmalloc() calls all over
> the vmalloc code, move it into alloc_vmap_area(). This will fix
> vm_map_ram() and simplify the code a bit.
> 
> Fixes: 3c5c3cfb9ef4 ("kasan: support backing vmalloc space with real shadow memory")
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> ---
> 
>  Changes since v1:
>   - Fix error path in alloc_vmap_area.
>   - Remove wrong Reported-by: syzbot (The issue reported by bot is a different one)
> 
>  include/linux/kasan.h | 15 +++++---
>  mm/kasan/common.c     | 27 +++++++++-----
>  mm/vmalloc.c          | 85 ++++++++++++++++++++-----------------------
>  3 files changed, 67 insertions(+), 60 deletions(-)
> 
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 4f404c565db1..e18fe54969e9 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -205,20 +205,23 @@ static inline void *kasan_reset_tag(const void *addr)
>  #endif /* CONFIG_KASAN_SW_TAGS */
>  
>  #ifdef CONFIG_KASAN_VMALLOC
> -int kasan_populate_vmalloc(unsigned long requested_size,
> -			   struct vm_struct *area);
> -void kasan_poison_vmalloc(void *start, unsigned long size);
> +int kasan_populate_vmalloc(unsigned long addr, unsigned long size);
> +void kasan_poison_vmalloc(const void *start, unsigned long size);
> +void kasan_unpoison_vmalloc(const void *start, unsigned long size);
>  void kasan_release_vmalloc(unsigned long start, unsigned long end,
>  			   unsigned long free_region_start,
>  			   unsigned long free_region_end);
>  #else
> -static inline int kasan_populate_vmalloc(unsigned long requested_size,
> -					 struct vm_struct *area)
> +static inline int kasan_populate_vmalloc(unsigned long start,
> +					unsigned long size)
>  {
>  	return 0;
>  }
>  
> -static inline void kasan_poison_vmalloc(void *start, unsigned long size) {}
> +static inline void kasan_poison_vmalloc(const void *start, unsigned long size)
> +{ }
> +static inline void kasan_unpoison_vmalloc(const void *start, unsigned long size)
> +{ }
>  static inline void kasan_release_vmalloc(unsigned long start,
>  					 unsigned long end,
>  					 unsigned long free_region_start,
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index df3371d5c572..a1e6273be8c3 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -777,15 +777,17 @@ static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
>  	return 0;
>  }
>  
> -int kasan_populate_vmalloc(unsigned long requested_size, struct vm_struct *area)
> +int kasan_populate_vmalloc(unsigned long addr, unsigned long size)
>  {
>  	unsigned long shadow_start, shadow_end;
>  	int ret;
>  
> -	shadow_start = (unsigned long)kasan_mem_to_shadow(area->addr);
> +	if (!is_vmalloc_or_module_addr((void *)addr))
> +		return 0;
> +
> +	shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr);
>  	shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
> -	shadow_end = (unsigned long)kasan_mem_to_shadow(area->addr +
> -							area->size);
> +	shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size);
>  	shadow_end = ALIGN(shadow_end, PAGE_SIZE);
>  
>  	ret = apply_to_page_range(&init_mm, shadow_start,
> @@ -796,10 +798,6 @@ int kasan_populate_vmalloc(unsigned long requested_size, struct vm_struct *area)
>  
>  	flush_cache_vmap(shadow_start, shadow_end);
>  
> -	kasan_unpoison_shadow(area->addr, requested_size);
> -
> -	area->flags |= VM_KASAN;
> -
>  	/*
>  	 * We need to be careful about inter-cpu effects here. Consider:
>  	 *
> @@ -842,12 +840,23 @@ int kasan_populate_vmalloc(unsigned long requested_size, struct vm_struct *area)
>   * Poison the shadow for a vmalloc region. Called as part of the
>   * freeing process at the time the region is freed.
>   */
> -void kasan_poison_vmalloc(void *start, unsigned long size)
> +void kasan_poison_vmalloc(const void *start, unsigned long size)
>  {
> +	if (!is_vmalloc_or_module_addr(start))
> +		return;
> +
>  	size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
>  	kasan_poison_shadow(start, size, KASAN_VMALLOC_INVALID);
>  }
>  
> +void kasan_unpoison_vmalloc(const void *start, unsigned long size)
> +{
> +	if (!is_vmalloc_or_module_addr(start))
> +		return;
> +
> +	kasan_unpoison_shadow(start, size);
> +}
> +
>  static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
>  					void *unused)
>  {
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 4d3b3d60d893..6e865cea846c 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1061,6 +1061,26 @@ __alloc_vmap_area(unsigned long size, unsigned long align,
>  	return nva_start_addr;
>  }
>  
> +/*
> + * Free a region of KVA allocated by alloc_vmap_area
> + */
> +static void free_vmap_area(struct vmap_area *va)
> +{
> +	/*
> +	 * Remove from the busy tree/list.
> +	 */
> +	spin_lock(&vmap_area_lock);
> +	unlink_va(va, &vmap_area_root);
> +	spin_unlock(&vmap_area_lock);
> +
> +	/*
> +	 * Insert/Merge it back to the free tree/list.
> +	 */
> +	spin_lock(&free_vmap_area_lock);
> +	merge_or_add_vmap_area(va, &free_vmap_area_root, &free_vmap_area_list);
> +	spin_unlock(&free_vmap_area_lock);
> +}
> +
>  /*
>   * Allocate a region of KVA of the specified size and alignment, within the
>   * vstart and vend.
> @@ -1073,6 +1093,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
>  	struct vmap_area *va, *pva;
>  	unsigned long addr;
>  	int purged = 0;
> +	int ret;
>  
>  	BUG_ON(!size);
>  	BUG_ON(offset_in_page(size));
> @@ -1139,6 +1160,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
>  	va->va_end = addr + size;
>  	va->vm = NULL;
>  
> +
>  	spin_lock(&vmap_area_lock);
>  	insert_vmap_area(va, &vmap_area_root, &vmap_area_list);
>  	spin_unlock(&vmap_area_lock);
> @@ -1147,6 +1169,12 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
>  	BUG_ON(va->va_start < vstart);
>  	BUG_ON(va->va_end > vend);
>  
> +	ret = kasan_populate_vmalloc(addr, size);
> +	if (ret) {
> +		free_vmap_area(va);
> +		return ERR_PTR(ret);
> +	}
> +
>  	return va;
>  
>  overflow:
> @@ -1185,26 +1213,6 @@ int unregister_vmap_purge_notifier(struct notifier_block *nb)
>  }
>  EXPORT_SYMBOL_GPL(unregister_vmap_purge_notifier);
>  
> -/*
> - * Free a region of KVA allocated by alloc_vmap_area
> - */
> -static void free_vmap_area(struct vmap_area *va)
> -{
> -	/*
> -	 * Remove from the busy tree/list.
> -	 */
> -	spin_lock(&vmap_area_lock);
> -	unlink_va(va, &vmap_area_root);
> -	spin_unlock(&vmap_area_lock);
> -
> -	/*
> -	 * Insert/Merge it back to the free tree/list.
> -	 */
> -	spin_lock(&free_vmap_area_lock);
> -	merge_or_add_vmap_area(va, &free_vmap_area_root, &free_vmap_area_list);
> -	spin_unlock(&free_vmap_area_lock);
> -}
> -
>  /*
>   * Clear the pagetable entries of a given vmap_area
>   */
> @@ -1771,6 +1779,8 @@ void vm_unmap_ram(const void *mem, unsigned int count)
>  	BUG_ON(addr > VMALLOC_END);
>  	BUG_ON(!PAGE_ALIGNED(addr));
>  
> +	kasan_poison_vmalloc(mem, size);
> +
>  	if (likely(count <= VMAP_MAX_ALLOC)) {
>  		debug_check_no_locks_freed(mem, size);
>  		vb_free(mem, size);
> @@ -1821,6 +1831,9 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node, pgprot_t pro
>  		addr = va->va_start;
>  		mem = (void *)addr;
>  	}
> +
> +	kasan_unpoison_vmalloc(mem, size);
> +
>  	if (vmap_page_range(addr, addr + size, prot, pages) < 0) {
>  		vm_unmap_ram(mem, count);
>  		return NULL;
> @@ -2075,6 +2088,7 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
>  {
>  	struct vmap_area *va;
>  	struct vm_struct *area;
> +	unsigned long requested_size = size;
>  
>  	BUG_ON(in_interrupt());
>  	size = PAGE_ALIGN(size);
> @@ -2098,23 +2112,9 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
>  		return NULL;
>  	}
>  
> -	setup_vmalloc_vm(area, va, flags, caller);
> +	kasan_unpoison_vmalloc((void *)va->va_start, requested_size);
>  
> -	/*
> -	 * For KASAN, if we are in vmalloc space, we need to cover the shadow
> -	 * area with real memory. If we come here through VM_ALLOC, this is
> -	 * done by a higher level function that has access to the true size,
> -	 * which might not be a full page.
> -	 *
> -	 * We assume module space comes via VM_ALLOC path.
> -	 */
> -	if (is_vmalloc_addr(area->addr) && !(area->flags & VM_ALLOC)) {
> -		if (kasan_populate_vmalloc(area->size, area)) {
> -			unmap_vmap_area(va);
> -			kfree(area);
> -			return NULL;
> -		}
> -	}
> +	setup_vmalloc_vm(area, va, flags, caller);
>  
>  	return area;
>  }
> @@ -2293,8 +2293,7 @@ static void __vunmap(const void *addr, int deallocate_pages)
>  	debug_check_no_locks_freed(area->addr, get_vm_area_size(area));
>  	debug_check_no_obj_freed(area->addr, get_vm_area_size(area));
>  
> -	if (area->flags & VM_KASAN)
> -		kasan_poison_vmalloc(area->addr, area->size);
> +	kasan_poison_vmalloc(area->addr, area->size);
>  
>  	vm_remove_mappings(area, deallocate_pages);
>  
> @@ -2539,7 +2538,7 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
>  	if (!size || (size >> PAGE_SHIFT) > totalram_pages())
>  		goto fail;
>  
> -	area = __get_vm_area_node(size, align, VM_ALLOC | VM_UNINITIALIZED |
> +	area = __get_vm_area_node(real_size, align, VM_ALLOC | VM_UNINITIALIZED |
>  				vm_flags, start, end, node, gfp_mask, caller);
>  	if (!area)
>  		goto fail;
> @@ -2548,11 +2547,6 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
>  	if (!addr)
>  		return NULL;
>  
> -	if (is_vmalloc_or_module_addr(area->addr)) {
> -		if (kasan_populate_vmalloc(real_size, area))
> -			return NULL;
> -	}
> -
>  	/*
>  	 * In this function, newly allocated vm_struct has VM_UNINITIALIZED
>  	 * flag. It means that vm_struct is not fully initialized.
> @@ -3437,7 +3431,8 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
>  	/* populate the shadow space outside of the lock */
>  	for (area = 0; area < nr_vms; area++) {
>  		/* assume success here */
> -		kasan_populate_vmalloc(sizes[area], vms[area]);
> +		kasan_populate_vmalloc(vas[area]->va_start, sizes[area]);
> +		kasan_unpoison_vmalloc((void *)vms[area]->addr, sizes[area]);
>  	}
>  
>  	kfree(vas);
> -- 
> 2.23.0
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

--
Vlad Rezki
>