kernel/memremap, kasan: make ZONE_DEVICE with work with KASAN

KASAN learns about hotadded memory via the memory hotplug notifier.
devm_memremap_pages() intentionally skips calling memory hotplug
notifiers.  So KASAN doesn't know anything about new memory added by
devm_memremap_pages().  This causes a crash when KASAN tries to access
non-existent shadow memory:

 BUG: unable to handle kernel paging request at ffffed0078000000
 RIP: 0010:check_memory_region+0x82/0x1e0
 Call Trace:
  memcpy+0x1f/0x50
  pmem_do_bvec+0x163/0x720
  pmem_make_request+0x305/0xac0
  generic_make_request+0x54f/0xcf0
  submit_bio+0x9c/0x370
  submit_bh_wbc+0x4c7/0x700
  block_read_full_page+0x5ef/0x870
  do_read_cache_page+0x2b8/0xb30
  read_dev_sector+0xbd/0x3f0
  read_lba.isra.0+0x277/0x670
  efi_partition+0x41a/0x18f0
  check_partition+0x30d/0x5e9
  rescan_partitions+0x18c/0x840
  __blkdev_get+0x859/0x1060
  blkdev_get+0x23f/0x810
  __device_add_disk+0x9c8/0xde0
  pmem_attach_disk+0x9a8/0xf50
  nvdimm_bus_probe+0xf3/0x3c0
  driver_probe_device+0x493/0xbd0
  bus_for_each_drv+0x118/0x1b0
  __device_attach+0x1cd/0x2b0
  bus_probe_device+0x1ac/0x260
  device_add+0x90d/0x1380
  nd_async_device_register+0xe/0x50
  async_run_entry_fn+0xc3/0x5d0
  process_one_work+0xa0a/0x1810
  worker_thread+0x87/0xe80
  kthread+0x2d7/0x390
  ret_from_fork+0x3a/0x50

Add kasan_add_zero_shadow()/kasan_remove_zero_shadow() - post mm_init()
interface to map/unmap kasan_zero_page at requested virtual addresses.
And use it to add/remove the shadow memory for hotplugged/unplugged
device memory.

Link: http://lkml.kernel.org/r/20180629164932.740-1-aryabinin@virtuozzo.com
Fixes: 41e94a851304 ("add devm_memremap_pages")
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reported-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Dan Williams <dan.j.williams@intel.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 303 insertions, 13 deletions

diff --git a/mm/kasan/kasan_init.c b/mm/kasan/kasan_init.c
index f436246ccc79..7a2a2f13f86f 100644
--- a/mm/kasan/kasan_init.c
+++ b/mm/kasan/kasan_init.c
@@ -17,10 +17,13 @@
 #include <linux/memblock.h>
 #include <linux/mm.h>
 #include <linux/pfn.h>
+#include <linux/slab.h>
 
 #include <asm/page.h>
 #include <asm/pgalloc.h>
 
+#include "kasan.h"
+
 /*
  * This page serves two purposes:
  *   - It used as early shadow memory. The entire shadow region populated
@@ -32,22 +35,59 @@ unsigned char kasan_zero_page[PAGE_SIZE] __page_aligned_bss;
 
 #if CONFIG_PGTABLE_LEVELS > 4
 p4d_t kasan_zero_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
+static inline bool kasan_p4d_table(pgd_t pgd)
+{
+        return pgd_page(pgd) == virt_to_page(lm_alias(kasan_zero_p4d));
+}
+#else
+static inline bool kasan_p4d_table(pgd_t pgd)
+{
+        return 0;
+}
 #endif
 #if CONFIG_PGTABLE_LEVELS > 3
 pud_t kasan_zero_pud[PTRS_PER_PUD] __page_aligned_bss;
+static inline bool kasan_pud_table(p4d_t p4d)
+{
+        return p4d_page(p4d) == virt_to_page(lm_alias(kasan_zero_pud));
+}
+#else
+static inline bool kasan_pud_table(p4d_t p4d)
+{
+        return 0;
+}
 #endif
 #if CONFIG_PGTABLE_LEVELS > 2
 pmd_t kasan_zero_pmd[PTRS_PER_PMD] __page_aligned_bss;
+static inline bool kasan_pmd_table(pud_t pud)
+{
+        return pud_page(pud) == virt_to_page(lm_alias(kasan_zero_pmd));
+}
+#else
+static inline bool kasan_pmd_table(pud_t pud)
+{
+        return 0;
+}
 #endif
 pte_t kasan_zero_pte[PTRS_PER_PTE] __page_aligned_bss;
 
+static inline bool kasan_pte_table(pmd_t pmd)
+{
+        return pmd_page(pmd) == virt_to_page(lm_alias(kasan_zero_pte));
+}
+
+static inline bool kasan_zero_page_entry(pte_t pte)
+{
+        return pte_page(pte) == virt_to_page(lm_alias(kasan_zero_page));
+}
+
 static __init void *early_alloc(size_t size, int node)
 {
         return memblock_virt_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
                                         BOOTMEM_ALLOC_ACCESSIBLE, node);
 }
 
-static void __init zero_pte_populate(pmd_t *pmd, unsigned long addr,
+static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
                                 unsigned long end)
 {
         pte_t *pte = pte_offset_kernel(pmd, addr);
@@ -63,7 +103,7 @@ static void __init zero_pte_populate(pmd_t *pmd, unsigned long addr,
         }
 }
 
-static void __init zero_pmd_populate(pud_t *pud, unsigned long addr,
+static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
                                 unsigned long end)
 {
         pmd_t *pmd = pmd_offset(pud, addr);
@@ -78,14 +118,24 @@ static void __init zero_pmd_populate(pud_t *pud, unsigned long addr,
                 }
 
                 if (pmd_none(*pmd)) {
-                        pmd_populate_kernel(&init_mm, pmd,
-                                        early_alloc(PAGE_SIZE, NUMA_NO_NODE));
+                        pte_t *p;
+
+                        if (slab_is_available())
+                                p = pte_alloc_one_kernel(&init_mm, addr);
+                        else
+                                p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
+                        if (!p)
+                                return -ENOMEM;
+
+                        pmd_populate_kernel(&init_mm, pmd, p);
                 }
                 zero_pte_populate(pmd, addr, next);
         } while (pmd++, addr = next, addr != end);
+
+        return 0;
 }
 
-static void __init zero_pud_populate(p4d_t *p4d, unsigned long addr,
+static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
                                 unsigned long end)
 {
         pud_t *pud = pud_offset(p4d, addr);
@@ -103,14 +153,24 @@ static void __init zero_pud_populate(p4d_t *p4d, unsigned long addr,
                 }
 
                 if (pud_none(*pud)) {
-                        pud_populate(&init_mm, pud,
-                                early_alloc(PAGE_SIZE, NUMA_NO_NODE));
+                        pmd_t *p;
+
+                        if (slab_is_available()) {
+                                p = pmd_alloc(&init_mm, pud, addr);
+                                if (!p)
+                                        return -ENOMEM;
+                        } else {
+                                pud_populate(&init_mm, pud,
+                                        early_alloc(PAGE_SIZE, NUMA_NO_NODE));
+                        }
                 }
                 zero_pmd_populate(pud, addr, next);
         } while (pud++, addr = next, addr != end);
+
+        return 0;
 }
 
-static void __init zero_p4d_populate(pgd_t *pgd, unsigned long addr,
+static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
                                 unsigned long end)
 {
         p4d_t *p4d = p4d_offset(pgd, addr);
@@ -132,11 +192,21 @@ static void __init zero_p4d_populate(pgd_t *pgd, unsigned long addr,
                 }
 
                 if (p4d_none(*p4d)) {
-                        p4d_populate(&init_mm, p4d,
-                                early_alloc(PAGE_SIZE, NUMA_NO_NODE));
+                        pud_t *p;
+
+                        if (slab_is_available()) {
+                                p = pud_alloc(&init_mm, p4d, addr);
+                                if (!p)
+                                        return -ENOMEM;
+                        } else {
+                                p4d_populate(&init_mm, p4d,
+                                        early_alloc(PAGE_SIZE, NUMA_NO_NODE));
+                        }
                 }
                 zero_pud_populate(p4d, addr, next);
         } while (p4d++, addr = next, addr != end);
+
+        return 0;
 }
 
 /**
@@ -145,7 +215,7 @@ static void __init zero_p4d_populate(pgd_t *pgd, unsigned long addr,
  * @shadow_start - start of the memory range to populate
  * @shadow_end   - end of the memory range to populate
  */
-void __init kasan_populate_zero_shadow(const void *shadow_start,
+int __ref kasan_populate_zero_shadow(const void *shadow_start,
                                 const void *shadow_end)
 {
         unsigned long addr = (unsigned long)shadow_start;
@@ -191,9 +261,229 @@ void __init kasan_populate_zero_shadow(const void *shadow_start,
                 }
 
                 if (pgd_none(*pgd)) {
-                        pgd_populate(&init_mm, pgd,
-                                early_alloc(PAGE_SIZE, NUMA_NO_NODE));
+                        p4d_t *p;
+
+                        if (slab_is_available()) {
+                                p = p4d_alloc(&init_mm, pgd, addr);
+                                if (!p)
+                                        return -ENOMEM;
+                        } else {
+                                pgd_populate(&init_mm, pgd,
+                                        early_alloc(PAGE_SIZE, NUMA_NO_NODE));
+                        }
                 }
                 zero_p4d_populate(pgd, addr, next);
         } while (pgd++, addr = next, addr != end);
+
+        return 0;
+}
+
+static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
+{
+        pte_t *pte;
+        int i;
+
+        for (i = 0; i < PTRS_PER_PTE; i++) {
+                pte = pte_start + i;
+                if (!pte_none(*pte))
+                        return;
+        }
+
+        pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
+        pmd_clear(pmd);
+}
+
+static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
+{
+        pmd_t *pmd;
+        int i;
+
+        for (i = 0; i < PTRS_PER_PMD; i++) {
+                pmd = pmd_start + i;
+                if (!pmd_none(*pmd))
+                        return;
+        }
+
+        pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
+        pud_clear(pud);
+}
+
+static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
+{
+        pud_t *pud;
+        int i;
+
+        for (i = 0; i < PTRS_PER_PUD; i++) {
+                pud = pud_start + i;
+                if (!pud_none(*pud))
+                        return;
+        }
+
+        pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
+        p4d_clear(p4d);
+}
+
+static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
+{
+        p4d_t *p4d;
+        int i;
+
+        for (i = 0; i < PTRS_PER_P4D; i++) {
+                p4d = p4d_start + i;
+                if (!p4d_none(*p4d))
+                        return;
+        }
+
+        p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
+        pgd_clear(pgd);
+}
+
+static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
+                                unsigned long end)
+{
+        unsigned long next;
+
+        for (; addr < end; addr = next, pte++) {
+                next = (addr + PAGE_SIZE) & PAGE_MASK;
+                if (next > end)
+                        next = end;
+
+                if (!pte_present(*pte))
+                        continue;
+
+                if (WARN_ON(!kasan_zero_page_entry(*pte)))
+                        continue;
+                pte_clear(&init_mm, addr, pte);
+        }
+}
+
+static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
+                                unsigned long end)
+{
+        unsigned long next;
+
+        for (; addr < end; addr = next, pmd++) {
+                pte_t *pte;
+
+                next = pmd_addr_end(addr, end);
+
+                if (!pmd_present(*pmd))
+                        continue;
+
+                if (kasan_pte_table(*pmd)) {
+                        if (IS_ALIGNED(addr, PMD_SIZE) &&
+                            IS_ALIGNED(next, PMD_SIZE))
+                                pmd_clear(pmd);
+                        continue;
+                }
+                pte = pte_offset_kernel(pmd, addr);
+                kasan_remove_pte_table(pte, addr, next);
+                kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
+        }
+}
+
+static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
+                                unsigned long end)
+{
+        unsigned long next;
+
+        for (; addr < end; addr = next, pud++) {
+                pmd_t *pmd, *pmd_base;
+
+                next = pud_addr_end(addr, end);
+
+                if (!pud_present(*pud))
+                        continue;
+
+                if (kasan_pmd_table(*pud)) {
+                        if (IS_ALIGNED(addr, PUD_SIZE) &&
+                            IS_ALIGNED(next, PUD_SIZE))
+                                pud_clear(pud);
+                        continue;
+                }
+                pmd = pmd_offset(pud, addr);
+                pmd_base = pmd_offset(pud, 0);
+                kasan_remove_pmd_table(pmd, addr, next);
+                kasan_free_pmd(pmd_base, pud);
+        }
+}
+
+static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
+                                unsigned long end)
+{
+        unsigned long next;
+
+        for (; addr < end; addr = next, p4d++) {
+                pud_t *pud;
+
+                next = p4d_addr_end(addr, end);
+
+                if (!p4d_present(*p4d))
+                        continue;
+
+                if (kasan_pud_table(*p4d)) {
+                        if (IS_ALIGNED(addr, P4D_SIZE) &&
+                            IS_ALIGNED(next, P4D_SIZE))
+                                p4d_clear(p4d);
+                        continue;
+                }
+                pud = pud_offset(p4d, addr);
+                kasan_remove_pud_table(pud, addr, next);
+                kasan_free_pud(pud_offset(p4d, 0), p4d);
+        }
+}
+
+void kasan_remove_zero_shadow(void *start, unsigned long size)
+{
+        unsigned long addr, end, next;
+        pgd_t *pgd;
+
+        addr = (unsigned long)kasan_mem_to_shadow(start);
+        end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
+
+        if (WARN_ON((unsigned long)start %
+                        (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)) ||
+            WARN_ON(size % (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)))
+                return;
+
+        for (; addr < end; addr = next) {
+                p4d_t *p4d;
+
+                next = pgd_addr_end(addr, end);
+
+                pgd = pgd_offset_k(addr);
+                if (!pgd_present(*pgd))
+                        continue;
+
+                if (kasan_p4d_table(*pgd)) {
+                        if (IS_ALIGNED(addr, PGDIR_SIZE) &&
+                            IS_ALIGNED(next, PGDIR_SIZE))
+                                pgd_clear(pgd);
+                        continue;
+                }
+
+                p4d = p4d_offset(pgd, addr);
+                kasan_remove_p4d_table(p4d, addr, next);
+                kasan_free_p4d(p4d_offset(pgd, 0), pgd);
+        }
+}
+
+int kasan_add_zero_shadow(void *start, unsigned long size)
+{
+        int ret;
+        void *shadow_start, *shadow_end;
+
+        shadow_start = kasan_mem_to_shadow(start);
+        shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
+
+        if (WARN_ON((unsigned long)start %
+                        (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)) ||
+            WARN_ON(size % (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)))
+                return -EINVAL;
+
+        ret = kasan_populate_zero_shadow(shadow_start, shadow_end);
+        if (ret)
+                kasan_remove_zero_shadow(shadow_start,
+                                        size >> KASAN_SHADOW_SCALE_SHIFT);
+        return ret;
 }