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Date: Mon, 9 Jul 2018 18:25:08 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: Dmitry Vyukov <dvyukov@...gle.com>
Cc: syzbot <syzbot+3f84280d52be9b7083cc@...kaller.appspotmail.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Dan Williams <dan.j.williams@...el.com>,
Jerome Glisse <jglisse@...hat.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
ldufour@...ux.vnet.ibm.com, LKML <linux-kernel@...r.kernel.org>,
Linux-MM <linux-mm@...ck.org>, Michal Hocko <mhocko@...e.com>,
Minchan Kim <minchan@...nel.org>,
Ross Zwisler <ross.zwisler@...ux.intel.com>,
syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
Matthew Wilcox <willy@...radead.org>, ying.huang@...el.com
Subject: Re: kernel BUG at mm/memory.c:LINE!
On Mon, Jul 09, 2018 at 05:21:55PM +0300, Kirill A. Shutemov wrote:
> > This also happened only once so far:
> > https://syzkaller.appspot.com/bug?extid=3f84280d52be9b7083cc
> > and I can't reproduce it rerunning this program. So it's either a very
> > subtle race, or fd in the middle of netlink address magically matched
> > some fd once, or something else...
>
> Okay, I've got it reproduced. See below.
>
> The problem is that kcov doesn't set vm_ops for the VMA and it makes
> kernel think that the VMA is anonymous.
>
> It's not necessary the way it was triggered by syzkaller. I just found
> that kcov's ->mmap doesn't set vm_ops. There can more such cases.
> vma_is_anonymous() is what we need to fix.
>
> ( Although, I found logic around mmaping the file second time questinable
> at best. It seems broken to me. )
>
> It is known that vma_is_anonymous() can produce false-positives. It tried
> to fix it once[1], but it back-fired[2].
>
> I'll look at this again.
Below is a patch that seems work. But it definately requires more testing.
Dmitry, could you give it a try in syzkaller?
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/kernfs/file.c b/fs/kernfs/file.c
index 2015d8c45e4a..945c3d306d8f 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -336,9 +336,6 @@ static void kernfs_vma_open(struct vm_area_struct *vma)
struct file *file = vma->vm_file;
struct kernfs_open_file *of = kernfs_of(file);
- if (!of->vm_ops)
- return;
-
if (!kernfs_get_active(of->kn))
return;
@@ -354,9 +351,6 @@ static vm_fault_t kernfs_vma_fault(struct vm_fault *vmf)
struct kernfs_open_file *of = kernfs_of(file);
vm_fault_t ret;
- if (!of->vm_ops)
- return VM_FAULT_SIGBUS;
-
if (!kernfs_get_active(of->kn))
return VM_FAULT_SIGBUS;
@@ -374,9 +368,6 @@ static vm_fault_t kernfs_vma_page_mkwrite(struct vm_fault *vmf)
struct kernfs_open_file *of = kernfs_of(file);
vm_fault_t ret;
- if (!of->vm_ops)
- return VM_FAULT_SIGBUS;
-
if (!kernfs_get_active(of->kn))
return VM_FAULT_SIGBUS;
@@ -397,9 +388,6 @@ static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr,
struct kernfs_open_file *of = kernfs_of(file);
int ret;
- if (!of->vm_ops)
- return -EINVAL;
-
if (!kernfs_get_active(of->kn))
return -EINVAL;
@@ -419,9 +407,6 @@ static int kernfs_vma_set_policy(struct vm_area_struct *vma,
struct kernfs_open_file *of = kernfs_of(file);
int ret;
- if (!of->vm_ops)
- return 0;
-
if (!kernfs_get_active(of->kn))
return -EINVAL;
@@ -440,9 +425,6 @@ static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma,
struct kernfs_open_file *of = kernfs_of(file);
struct mempolicy *pol;
- if (!of->vm_ops)
- return vma->vm_policy;
-
if (!kernfs_get_active(of->kn))
return vma->vm_policy;
@@ -511,7 +493,7 @@ static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
* So error if someone is trying to use close.
*/
rc = -EINVAL;
- if (vma->vm_ops && vma->vm_ops->close)
+ if (vma->vm_ops->close)
goto out_put;
rc = 0;
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index e9679016271f..e959623123e4 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -326,7 +326,7 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma, int is_pid)
goto done;
}
- if (vma->vm_ops && vma->vm_ops->name) {
+ if (vma->vm_ops->name) {
name = vma->vm_ops->name(vma);
if (name)
goto done;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a0fbb9ffe380..f1db03c919c3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1536,9 +1536,11 @@ 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;
+
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/kernel/events/core.c b/kernel/events/core.c
index 8f0434a9951a..2e35401a5c68 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7269,7 +7269,7 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
goto got_name;
} else {
- if (vma->vm_ops && vma->vm_ops->name) {
+ if (vma->vm_ops->name) {
name = (char *) vma->vm_ops->name(vma);
if (name)
goto cpy_name;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 039ddbc574e9..2065acc5a6aa 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -637,7 +637,7 @@ EXPORT_SYMBOL_GPL(linear_hugepage_index);
*/
unsigned long vma_kernel_pagesize(struct vm_area_struct *vma)
{
- if (vma->vm_ops && vma->vm_ops->pagesize)
+ if (vma->vm_ops->pagesize)
return vma->vm_ops->pagesize(vma);
return PAGE_SIZE;
}
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/memory.c b/mm/memory.c
index 7206a634270b..02fbef2bd024 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -768,7 +768,7 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
(void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
pr_alert("file:%pD fault:%pf mmap:%pf readpage:%pf\n",
vma->vm_file,
- vma->vm_ops ? vma->vm_ops->fault : NULL,
+ vma->vm_ops->fault,
vma->vm_file ? vma->vm_file->f_op->mmap : NULL,
mapping ? mapping->a_ops->readpage : NULL);
dump_stack();
@@ -825,7 +825,7 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) {
if (likely(!pte_special(pte)))
goto check_pfn;
- if (vma->vm_ops && vma->vm_ops->find_special_page)
+ if (vma->vm_ops->find_special_page)
return vma->vm_ops->find_special_page(vma, addr);
if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
return NULL;
@@ -2404,7 +2404,7 @@ static void fault_dirty_shared_page(struct vm_area_struct *vma,
{
struct address_space *mapping;
bool dirtied;
- bool page_mkwrite = vma->vm_ops && vma->vm_ops->page_mkwrite;
+ bool page_mkwrite = vma->vm_ops->page_mkwrite;
dirtied = set_page_dirty(page);
VM_BUG_ON_PAGE(PageAnon(page), page);
@@ -2648,7 +2648,7 @@ static int wp_pfn_shared(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
- if (vma->vm_ops && vma->vm_ops->pfn_mkwrite) {
+ if (vma->vm_ops->pfn_mkwrite) {
int ret;
pte_unmap_unlock(vmf->pte, vmf->ptl);
@@ -2669,7 +2669,7 @@ static int wp_page_shared(struct vm_fault *vmf)
get_page(vmf->page);
- if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
+ if (vma->vm_ops->page_mkwrite) {
int tmp;
pte_unmap_unlock(vmf->pte, vmf->ptl);
@@ -4439,7 +4439,7 @@ int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
vma = find_vma(mm, addr);
if (!vma || vma->vm_start > addr)
break;
- if (vma->vm_ops && vma->vm_ops->access)
+ if (vma->vm_ops->access)
ret = vma->vm_ops->access(vma, addr, buf,
len, write);
if (ret <= 0)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 9ac49ef17b4e..f0fcf70bcec7 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -651,13 +651,13 @@ static int vma_replace_policy(struct vm_area_struct *vma,
pr_debug("vma %lx-%lx/%lx vm_ops %p vm_file %p set_policy %p\n",
vma->vm_start, vma->vm_end, vma->vm_pgoff,
vma->vm_ops, vma->vm_file,
- vma->vm_ops ? vma->vm_ops->set_policy : NULL);
+ vma->vm_ops->set_policy);
new = mpol_dup(pol);
if (IS_ERR(new))
return PTR_ERR(new);
- if (vma->vm_ops && vma->vm_ops->set_policy) {
+ if (vma->vm_ops->set_policy) {
err = vma->vm_ops->set_policy(vma, new);
if (err)
goto err_out;
@@ -845,7 +845,7 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask,
up_read(&mm->mmap_sem);
return -EFAULT;
}
- if (vma->vm_ops && vma->vm_ops->get_policy)
+ if (vma->vm_ops->get_policy)
pol = vma->vm_ops->get_policy(vma, addr);
else
pol = vma->vm_policy;
@@ -1617,7 +1617,7 @@ struct mempolicy *__get_vma_policy(struct vm_area_struct *vma,
struct mempolicy *pol = NULL;
if (vma) {
- if (vma->vm_ops && vma->vm_ops->get_policy) {
+ if (vma->vm_ops->get_policy) {
pol = vma->vm_ops->get_policy(vma, addr);
} else if (vma->vm_policy) {
pol = vma->vm_policy;
@@ -1663,7 +1663,7 @@ bool vma_policy_mof(struct vm_area_struct *vma)
{
struct mempolicy *pol;
- if (vma->vm_ops && vma->vm_ops->get_policy) {
+ if (vma->vm_ops->get_policy) {
bool ret = false;
pol = vma->vm_ops->get_policy(vma, vma->vm_start);
diff --git a/mm/mmap.c b/mm/mmap.c
index d1eb87ef4b1a..516fb5c5bfe5 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -71,6 +71,8 @@ int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
static bool ignore_rlimit_data;
core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
+const struct vm_operations_struct anon_vm_ops = {};
+
static void unmap_region(struct mm_struct *mm,
struct vm_area_struct *vma, struct vm_area_struct *prev,
unsigned long start, unsigned long end);
@@ -177,7 +179,7 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
struct vm_area_struct *next = vma->vm_next;
might_sleep();
- if (vma->vm_ops && vma->vm_ops->close)
+ if (vma->vm_ops->close)
vma->vm_ops->close(vma);
if (vma->vm_file)
fput(vma->vm_file);
@@ -561,6 +563,8 @@ 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);
@@ -996,7 +1000,7 @@ static inline int is_mergeable_vma(struct vm_area_struct *vma,
return 0;
if (vma->vm_file != file)
return 0;
- if (vma->vm_ops && vma->vm_ops->close)
+ if (vma->vm_ops->close)
return 0;
if (!is_mergeable_vm_userfaultfd_ctx(vma, vm_userfaultfd_ctx))
return 0;
@@ -1636,7 +1640,7 @@ int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
return 0;
/* The backer wishes to know when pages are first written to? */
- if (vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite))
+ if (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite)
return 1;
/* The open routine did something to the protections that pgprot_modify
@@ -1774,12 +1778,20 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
*/
WARN_ON_ONCE(addr != vma->vm_start);
+ /* All mappings must have ->vm_ops set */
+ if (!vma->vm_ops) {
+ static const struct vm_operations_struct dummy_ops = {};
+ vma->vm_ops = &dummy_ops;
+ }
+
addr = vma->vm_start;
vm_flags = vma->vm_flags;
} else if (vm_flags & VM_SHARED) {
error = shmem_zero_setup(vma);
if (error)
goto free_vma;
+ } else {
+ vma->vm_ops = &anon_vm_ops;
}
vma_link(mm, vma, prev, rb_link, rb_parent);
@@ -2614,7 +2626,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
struct vm_area_struct *new;
int err;
- if (vma->vm_ops && vma->vm_ops->split) {
+ if (vma->vm_ops->split) {
err = vma->vm_ops->split(vma, addr);
if (err)
return err;
@@ -2647,7 +2659,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
if (new->vm_file)
get_file(new->vm_file);
- if (new->vm_ops && new->vm_ops->open)
+ if (new->vm_ops->open)
new->vm_ops->open(new);
if (new_below)
@@ -2661,7 +2673,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
return 0;
/* Clean everything up if vma_adjust failed. */
- if (new->vm_ops && new->vm_ops->close)
+ if (new->vm_ops->close)
new->vm_ops->close(new);
if (new->vm_file)
fput(new->vm_file);
@@ -2999,6 +3011,7 @@ 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;
@@ -3221,7 +3234,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
goto out_free_mempol;
if (new_vma->vm_file)
get_file(new_vma->vm_file);
- if (new_vma->vm_ops && new_vma->vm_ops->open)
+ if (new_vma->vm_ops->open)
new_vma->vm_ops->open(new_vma);
vma_link(mm, new_vma, prev, rb_link, rb_parent);
*need_rmap_locks = false;
diff --git a/mm/mremap.c b/mm/mremap.c
index 5c2e18505f75..7ab222c283de 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -302,7 +302,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,
need_rmap_locks);
if (moved_len < old_len) {
err = -ENOMEM;
- } else if (vma->vm_ops && vma->vm_ops->mremap) {
+ } else if (vma->vm_ops->mremap) {
err = vma->vm_ops->mremap(new_vma);
}
diff --git a/mm/nommu.c b/mm/nommu.c
index 4452d8bd9ae4..e7f447bfd704 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -764,7 +764,7 @@ static void delete_vma_from_mm(struct vm_area_struct *vma)
*/
static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)
{
- if (vma->vm_ops && vma->vm_ops->close)
+ if (vma->vm_ops->close)
vma->vm_ops->close(vma);
if (vma->vm_file)
fput(vma->vm_file);
@@ -1489,7 +1489,7 @@ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
region->vm_pgoff = new->vm_pgoff += npages;
}
- if (new->vm_ops && new->vm_ops->open)
+ if (new->vm_ops->open)
new->vm_ops->open(new);
delete_vma_from_mm(vma);
diff --git a/mm/shmem.c b/mm/shmem.c
index 2cab84403055..bf991c9230b3 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 = &anon_vm_ops;
}
static void shmem_pseudo_vma_destroy(struct vm_area_struct *vma)
--
Kirill A. Shutemov
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