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From: Andrey Ryabinin <aryabinin@virtuozzo.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Menzel <pmenzel+linux-kasan-dev@molgen.mpg.de>,
	Alexander Potapenko <glider@google.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, Andrey Ryabinin <aryabinin@virtuozzo.com>,
	stable@vger.kernel.org
Subject: [PATCH] mm/kasan: Don't vfree() nonexistent vm_area.
Date: Thu,  1 Feb 2018 19:33:49 +0300	[thread overview]
Message-ID: <20180201163349.8700-1-aryabinin@virtuozzo.com> (raw)
In-Reply-To: <12c9e499-9c11-d248-6a3f-14ec8c4e07f1@molgen.mpg.de>

KASAN uses different routines to map shadow for hot added memory and memory
obtained in boot process. Attempt to offline memory onlined by normal boot
process leads to this:

    Trying to vfree() nonexistent vm area (000000005d3b34b9)
    WARNING: CPU: 2 PID: 13215 at mm/vmalloc.c:1525 __vunmap+0x147/0x190

    Call Trace:
     kasan_mem_notifier+0xad/0xb9
     notifier_call_chain+0x166/0x260
     __blocking_notifier_call_chain+0xdb/0x140
     __offline_pages+0x96a/0xb10
     memory_subsys_offline+0x76/0xc0
     device_offline+0xb8/0x120
     store_mem_state+0xfa/0x120
     kernfs_fop_write+0x1d5/0x320
     __vfs_write+0xd4/0x530
     vfs_write+0x105/0x340
     SyS_write+0xb0/0x140

Obviously we can't call vfree() to free memory that wasn't allocated via
vmalloc(). Use find_vm_area() to see if we can call vfree().

Unfortunately it's a bit tricky to properly unmap and free shadow allocated
during boot, so we'll have to keep it. If memory will come online again
that shadow will be reused.

Fixes: fa69b5989bb0 ("mm/kasan: add support for memory hotplug")
Reported-by: Paul Menzel <pmenzel+linux-kasan-dev@molgen.mpg.de>
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: <stable@vger.kernel.org>
---
 mm/kasan/kasan.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 55 insertions(+), 2 deletions(-)

diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index e13d911251e7..0d9d9d268f32 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -791,6 +791,41 @@ DEFINE_ASAN_SET_SHADOW(f5);
 DEFINE_ASAN_SET_SHADOW(f8);
 
 #ifdef CONFIG_MEMORY_HOTPLUG
+static bool shadow_mapped(unsigned long addr)
+{
+	pgd_t *pgd = pgd_offset_k(addr);
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+
+	if (pgd_none(*pgd))
+		return false;
+	p4d = p4d_offset(pgd, addr);
+	if (p4d_none(*p4d))
+		return false;
+	pud = pud_offset(p4d, addr);
+	if (pud_none(*pud))
+		return false;
+
+	/*
+	 * We can't use pud_large() or pud_huge(), the first one
+	 * is arch-specific, the last one depend on HUGETLB_PAGE.
+	 * So let's abuse pud_bad(), if bud is bad it's has to
+	 * because it's huge.
+	 */
+	if (pud_bad(*pud))
+		return true;
+	pmd = pmd_offset(pud, addr);
+	if (pmd_none(*pmd))
+		return false;
+
+	if (pmd_bad(*pmd))
+		return true;
+	pte = pte_offset_kernel(pmd, addr);
+	return !pte_none(*pte);
+}
+
 static int __meminit kasan_mem_notifier(struct notifier_block *nb,
 			unsigned long action, void *data)
 {
@@ -812,6 +847,14 @@ static int __meminit kasan_mem_notifier(struct notifier_block *nb,
 	case MEM_GOING_ONLINE: {
 		void *ret;
 
+		/*
+		 * If shadow is mapped already than it must have been mapped
+		 * during the boot. This could happen if we onlining previously
+		 * offlined memory.
+		 */
+		if (shadow_mapped(shadow_start))
+			return NOTIFY_OK;
+
 		ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
 					shadow_end, GFP_KERNEL,
 					PAGE_KERNEL, VM_NO_GUARD,
@@ -823,8 +866,18 @@ static int __meminit kasan_mem_notifier(struct notifier_block *nb,
 		kmemleak_ignore(ret);
 		return NOTIFY_OK;
 	}
-	case MEM_OFFLINE:
-		vfree((void *)shadow_start);
+	case MEM_OFFLINE: {
+		struct vm_struct *vm;
+
+		/*
+		 * Only hot-added memory have vm_area. Freeing shadow
+		 * mapped during boot would be tricky, so we'll just
+		 * have to keep it.
+		 */
+		vm = find_vm_area((void *)shadow_start);
+		if (vm)
+			vfree((void *)shadow_start);
+	}
 	}
 
 	return NOTIFY_OK;
-- 
2.13.6

  reply	other threads:[~2018-02-01 16:33 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-31 16:46 Trying to vfree() nonexistent vm area (000000005d3b34b9) Paul Menzel
2018-02-01 16:33 ` Andrey Ryabinin [this message]
2018-02-01 19:57   ` [PATCH] mm/kasan: Don't vfree() nonexistent vm_area Matthew Wilcox
2018-02-01 20:22     ` Andrey Ryabinin
2018-02-02 17:20       ` Matthew Wilcox
2018-02-05  8:48         ` Andrey Ryabinin
2018-05-18 15:57   ` David Hildenbrand
2018-05-18 16:01     ` David Hildenbrand
2018-05-22 16:44   ` Andrey Ryabinin
2018-05-22 21:03     ` Andrew Morton
2018-05-23 12:33       ` Andrey Ryabinin
2018-05-26  3:31         ` [PATCH] mm-kasan-dont-vfree-nonexistent-vm_area-fix kbuild test robot
2018-05-26  3:48           ` Andrew Morton
2018-05-28  4:13             ` Ian Kent
2018-05-28  4:39               ` Ian Kent
2018-05-29  4:01                 ` Ian Kent
2018-05-30 11:53         ` kbuild test robot

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