[PATCHv2 1/2] mm: Fix vma_is_anonymous() false-positives
From: Kirill A. Shutemov
Date: Thu Jul 12 2018 - 10:56:47 EST
vma_is_anonymous() relies on ->vm_ops being NULL to detect anonymous
VMA. This is unreliable as ->mmap may not set ->vm_ops.
False-positive vma_is_anonymous() may lead to crashes:
next ffff8801ce5e7040 prev ffff8801d20eca50 mm ffff88019c1e13c0
prot 27 anon_vma ffff88019680cdd8 vm_ops 0000000000000000
pgoff 0 file ffff8801b2ec2d00 private_data 0000000000000000
flags: 0xff(read|write|exec|shared|mayread|maywrite|mayexec|mayshare)
------------[ cut here ]------------
kernel BUG at mm/memory.c:1422!
invalid opcode: 0000 [#1] SMP KASAN
CPU: 0 PID: 18486 Comm: syz-executor3 Not tainted 4.18.0-rc3+ #136
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google
01/01/2011
RIP: 0010:zap_pmd_range mm/memory.c:1421 [inline]
RIP: 0010:zap_pud_range mm/memory.c:1466 [inline]
RIP: 0010:zap_p4d_range mm/memory.c:1487 [inline]
RIP: 0010:unmap_page_range+0x1c18/0x2220 mm/memory.c:1508
Code: ff 31 ff 4c 89 e6 42 c6 04 33 f8 e8 92 dd d0 ff 4d 85 e4 0f 85 4a eb ff
ff e8 54 dc d0 ff 48 8b bd 10 fc ff ff e8 82 95 fe ff <0f> 0b e8 41 dc d0 ff
0f 0b 4c 89 ad 18 fc ff ff c7 85 7c fb ff ff
RSP: 0018:ffff8801b0587330 EFLAGS: 00010286
RAX: 000000000000013c RBX: 1ffff100360b0e9c RCX: ffffc90002620000
RDX: 0000000000000000 RSI: ffffffff81631851 RDI: 0000000000000001
RBP: ffff8801b05877c8 R08: ffff880199d40300 R09: ffffed003b5c4fc0
R10: ffffed003b5c4fc0 R11: ffff8801dae27e07 R12: 0000000000000000
R13: ffff88019c1e13c0 R14: dffffc0000000000 R15: 0000000020e01000
FS: 00007fca32251700(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f04c540d000 CR3: 00000001ac1f0000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
unmap_single_vma+0x1a0/0x310 mm/memory.c:1553
zap_page_range_single+0x3cc/0x580 mm/memory.c:1644
unmap_mapping_range_vma mm/memory.c:2792 [inline]
unmap_mapping_range_tree mm/memory.c:2813 [inline]
unmap_mapping_pages+0x3a7/0x5b0 mm/memory.c:2845
unmap_mapping_range+0x48/0x60 mm/memory.c:2880
truncate_pagecache+0x54/0x90 mm/truncate.c:800
truncate_setsize+0x70/0xb0 mm/truncate.c:826
simple_setattr+0xe9/0x110 fs/libfs.c:409
notify_change+0xf13/0x10f0 fs/attr.c:335
do_truncate+0x1ac/0x2b0 fs/open.c:63
do_sys_ftruncate+0x492/0x560 fs/open.c:205
__do_sys_ftruncate fs/open.c:215 [inline]
__se_sys_ftruncate fs/open.c:213 [inline]
__x64_sys_ftruncate+0x59/0x80 fs/open.c:213
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Reproducer:
#include <stdio.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <unistd.h>
#include <fcntl.h>
#define KCOV_INIT_TRACE _IOR('c', 1, unsigned long)
#define KCOV_ENABLE _IO('c', 100)
#define KCOV_DISABLE _IO('c', 101)
#define COVER_SIZE (1024<<10)
#define KCOV_TRACE_PC 0
#define KCOV_TRACE_CMP 1
int main(int argc, char **argv)
{
int fd;
unsigned long *cover;
system("mount -t debugfs none /sys/kernel/debug");
fd = open("/sys/kernel/debug/kcov", O_RDWR);
ioctl(fd, KCOV_INIT_TRACE, COVER_SIZE);
cover = mmap(NULL, COVER_SIZE * sizeof(unsigned long),
PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
munmap(cover, COVER_SIZE * sizeof(unsigned long));
cover = mmap(NULL, COVER_SIZE * sizeof(unsigned long),
PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
memset(cover, 0, COVER_SIZE * sizeof(unsigned long));
ftruncate(fd, 3UL << 20);
return 0;
}
This can be fixed by assigning anonymous VMAs own vm_ops and not relying
on it being NULL.
If ->mmap() failed to set ->vm_ops, mmap_region() will set it to
dummy_vm_ops. This way we will have non-NULL ->vm_ops for all VMAs.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reported-by: syzbot+3f84280d52be9b7083cc@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
---
arch/ia64/kernel/perfmon.c | 1 +
arch/ia64/mm/init.c | 2 ++
drivers/char/mem.c | 1 +
fs/exec.c | 1 +
fs/hugetlbfs/inode.c | 1 +
include/linux/mm.h | 5 ++++-
mm/khugepaged.c | 4 ++--
mm/mmap.c | 11 +++++++++++
mm/nommu.c | 9 ++++++++-
mm/shmem.c | 1 +
mm/util.c | 12 ++++++++++++
11 files changed, 44 insertions(+), 4 deletions(-)
diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
index 3b38c717008a..13fd6f7d37e8 100644
--- a/arch/ia64/kernel/perfmon.c
+++ b/arch/ia64/kernel/perfmon.c
@@ -2292,6 +2292,7 @@ pfm_smpl_buffer_alloc(struct task_struct *task, struct file *filp, pfm_context_t
vma->vm_file = get_file(filp);
vma->vm_flags = VM_READ|VM_MAYREAD|VM_DONTEXPAND|VM_DONTDUMP;
vma->vm_page_prot = PAGE_READONLY; /* XXX may need to change */
+ vma->vm_ops = &dummy_vm_ops;
/*
* Now we have everything we need and we can initialize
diff --git a/arch/ia64/mm/init.c b/arch/ia64/mm/init.c
index 18278b448530..f5dfcb723518 100644
--- a/arch/ia64/mm/init.c
+++ b/arch/ia64/mm/init.c
@@ -122,6 +122,7 @@ ia64_init_addr_space (void)
vma->vm_end = vma->vm_start + PAGE_SIZE;
vma->vm_flags = VM_DATA_DEFAULT_FLAGS|VM_GROWSUP|VM_ACCOUNT;
vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
+ vma->vm_ops = &dummy_vm_ops;
down_write(¤t->mm->mmap_sem);
if (insert_vm_struct(current->mm, vma)) {
up_write(¤t->mm->mmap_sem);
@@ -141,6 +142,7 @@ ia64_init_addr_space (void)
vma->vm_page_prot = __pgprot(pgprot_val(PAGE_READONLY) | _PAGE_MA_NAT);
vma->vm_flags = VM_READ | VM_MAYREAD | VM_IO |
VM_DONTEXPAND | VM_DONTDUMP;
+ vma->vm_ops = &dummy_vm_ops;
down_write(¤t->mm->mmap_sem);
if (insert_vm_struct(current->mm, vma)) {
up_write(¤t->mm->mmap_sem);
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index ffeb60d3434c..f0a8b0b1768b 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -708,6 +708,7 @@ static int mmap_zero(struct file *file, struct vm_area_struct *vma)
#endif
if (vma->vm_flags & VM_SHARED)
return shmem_zero_setup(vma);
+ vma->vm_ops = &anon_vm_ops;
return 0;
}
diff --git a/fs/exec.c b/fs/exec.c
index 2d4e0075bd24..a1a246062561 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -307,6 +307,7 @@ static int __bprm_mm_init(struct linux_binprm *bprm)
* configured yet.
*/
BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
+ vma->vm_ops = &anon_vm_ops;
vma->vm_end = STACK_TOP_MAX;
vma->vm_start = vma->vm_end - PAGE_SIZE;
vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index d508c7844681..5ff73b1398ad 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -597,6 +597,7 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
memset(&pseudo_vma, 0, sizeof(struct vm_area_struct));
pseudo_vma.vm_flags = (VM_HUGETLB | VM_MAYSHARE | VM_SHARED);
pseudo_vma.vm_file = file;
+ pseudo_vma.vm_ops = &dummy_vm_ops;
for (index = start; index < end; index++) {
/*
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a0fbb9ffe380..9a35362bbc92 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1536,9 +1536,12 @@ int clear_page_dirty_for_io(struct page *page);
int get_cmdline(struct task_struct *task, char *buffer, int buflen);
+extern const struct vm_operations_struct anon_vm_ops;
+extern const struct vm_operations_struct dummy_vm_ops;
+
static inline bool vma_is_anonymous(struct vm_area_struct *vma)
{
- return !vma->vm_ops;
+ return vma->vm_ops == &anon_vm_ops;
}
#ifdef CONFIG_SHMEM
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index d7b2a4bf8671..5ae34097aed1 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -440,7 +440,7 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
* page fault if needed.
*/
return 0;
- if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED))
+ if (!vma_is_anonymous(vma) || (vm_flags & VM_NO_KHUGEPAGED))
/* khugepaged not yet working on file or special mappings */
return 0;
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
@@ -831,7 +831,7 @@ static bool hugepage_vma_check(struct vm_area_struct *vma)
return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
HPAGE_PMD_NR);
}
- if (!vma->anon_vma || vma->vm_ops)
+ if (!vma->anon_vma || !vma_is_anonymous(vma))
return false;
if (is_vma_temporary_stack(vma))
return false;
diff --git a/mm/mmap.c b/mm/mmap.c
index d1eb87ef4b1a..527c17f31635 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -561,6 +561,8 @@ static unsigned long count_vma_pages_range(struct mm_struct *mm,
void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
struct rb_node **rb_link, struct rb_node *rb_parent)
{
+ WARN_ONCE(!vma->vm_ops, "missing vma->vm_ops");
+
/* Update tracking information for the gap following the new vma. */
if (vma->vm_next)
vma_gap_update(vma->vm_next);
@@ -1762,6 +1764,11 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
*/
vma->vm_file = get_file(file);
error = call_mmap(file, vma);
+
+ /* All mappings must have ->vm_ops set */
+ if (!vma->vm_ops)
+ vma->vm_ops = &dummy_vm_ops;
+
if (error)
goto unmap_and_free_vma;
@@ -1780,6 +1787,9 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
error = shmem_zero_setup(vma);
if (error)
goto free_vma;
+ } else {
+ /* vma_is_anonymous() relies on this. */
+ vma->vm_ops = &anon_vm_ops;
}
vma_link(mm, vma, prev, rb_link, rb_parent);
@@ -2999,6 +3009,7 @@ static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long
INIT_LIST_HEAD(&vma->anon_vma_chain);
vma->vm_mm = mm;
+ vma->vm_ops = &anon_vm_ops;
vma->vm_start = addr;
vma->vm_end = addr + len;
vma->vm_pgoff = pgoff;
diff --git a/mm/nommu.c b/mm/nommu.c
index 4452d8bd9ae4..f00f209833ab 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1058,6 +1058,8 @@ static int do_mmap_shared_file(struct vm_area_struct *vma)
int ret;
ret = call_mmap(vma->vm_file, vma);
+ if (!vma->vm_ops)
+ vma->vm_ops = &dummy_vm_ops;
if (ret == 0) {
vma->vm_region->vm_top = vma->vm_region->vm_end;
return 0;
@@ -1089,6 +1091,8 @@ static int do_mmap_private(struct vm_area_struct *vma,
*/
if (capabilities & NOMMU_MAP_DIRECT) {
ret = call_mmap(vma->vm_file, vma);
+ if (!vma->vm_ops)
+ vma->vm_ops = &dummy_vm_ops;
if (ret == 0) {
/* shouldn't return success if we're not sharing */
BUG_ON(!(vma->vm_flags & VM_MAYSHARE));
@@ -1137,6 +1141,8 @@ static int do_mmap_private(struct vm_area_struct *vma,
fpos = vma->vm_pgoff;
fpos <<= PAGE_SHIFT;
+ vma->vm_ops = &dummy_vm_ops;
+
ret = kernel_read(vma->vm_file, base, len, &fpos);
if (ret < 0)
goto error_free;
@@ -1144,7 +1150,8 @@ static int do_mmap_private(struct vm_area_struct *vma,
/* clear the last little bit */
if (ret < len)
memset(base + ret, 0, len - ret);
-
+ } else {
+ vma->vm_ops = &anon_vm_ops;
}
return 0;
diff --git a/mm/shmem.c b/mm/shmem.c
index 2cab84403055..db5c319161ca 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1424,6 +1424,7 @@ static void shmem_pseudo_vma_init(struct vm_area_struct *vma,
/* Bias interleave by inode number to distribute better across nodes */
vma->vm_pgoff = index + info->vfs_inode.i_ino;
vma->vm_policy = mpol_shared_policy_lookup(&info->policy, index);
+ vma->vm_ops = &dummy_vm_ops;
}
static void shmem_pseudo_vma_destroy(struct vm_area_struct *vma)
diff --git a/mm/util.c b/mm/util.c
index 3351659200e6..20e6a78f3237 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -20,6 +20,18 @@
#include "internal.h"
+/*
+ * All anonymous VMAs have ->vm_ops set to anon_vm_ops.
+ * vma_is_anonymous() reiles on anon_vm_ops to detect anonymous VMA.
+ */
+const struct vm_operations_struct anon_vm_ops = {};
+
+/*
+ * All VMAs have to have ->vm_ops set. dummy_vm_ops can be used if the VMA
+ * doesn't need to handle any of the operations.
+ */
+const struct vm_operations_struct dummy_vm_ops = {};
+
static inline int is_kernel_rodata(unsigned long addr)
{
return addr >= (unsigned long)__start_rodata &&
--
2.18.0