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SubjectRe: [PATCH] error path in setup_arg_pages() misses vm_unacct_memory()
On Tue, 13 Sep 2005, Hugh Dickins wrote:
> On Mon, 12 Sep 2005, Andrew Morton wrote:
> >
> > Patch looks OK to me. Hugh, could you please double-check sometime?
>
> It's a good find, and the patch looks correct to me, so far as it goes.
> But I think it's the wrong patch, and incomplete: it can be done more
> appropriately, more simply and more completely in insert_vm_struct itself.
> I'll post a replacement patch (or admit I'm wrong) in a little while.

Many thanks, Andrew, for confirming that ppc64 does indeed leak into
Committed_AS, as it looked to me. Here's my version of Pavel/Kirill's
patches: sorry if it seems "weird" to Kirill, perhaps we need to change
the name of insert_vm_struct too; but it seems safer and easier to get
right this way. And I prefer deleting code to adding it...


Pavel Emelianov and Kirill Korotaev observe that fs and arch users of
security_vm_enough_memory tend to forget to vm_unacct_memory when a
failure occurs further down (typically in setup_arg_pages variants).

These are all users of insert_vm_struct, and that reservation will only
be unaccounted on exit if the vma is marked VM_ACCOUNT: which in some
cases it is (hidden inside VM_STACK_FLAGS) and in some cases it isn't.

So x86_64 32-bit and ppc64 vDSO ELFs have been leaking memory into
Committed_AS each time they're run. But don't add VM_ACCOUNT to them,
it's inappropriate to reserve against the very unlikely case that gdb
be used to COW a vDSO page - we ought to do something about that in
do_wp_page, but there are yet other inconsistencies to be resolved.

The safe and economical way to fix this is to let insert_vm_struct do
the security_vm_enough_memory check when it finds VM_ACCOUNT is set.

And the MIPS irix_brk has been calling security_vm_enough_memory before
calling do_brk which repeats it, doubly accounting and so also leaking.
Remove that, and all the fs and arch calls to security_vm_enough_memory:
give it a less misleading name later on.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
---

arch/ia64/ia32/binfmt_elf32.c | 6 ------
arch/mips/kernel/sysirix.c | 9 ++-------
arch/ppc64/kernel/vdso.c | 15 +++++++++------
arch/x86_64/ia32/ia32_binfmt.c | 5 -----
arch/x86_64/ia32/syscall32.c | 6 +-----
fs/exec.c | 5 -----
mm/mmap.c | 3 +++
7 files changed, 15 insertions(+), 34 deletions(-)

--- 2.6.14-rc1/arch/ia64/ia32/binfmt_elf32.c 2005-03-02 07:39:16.000000000 +0000
+++ linux/arch/ia64/ia32/binfmt_elf32.c 2005-09-13 17:58:28.000000000 +0100
@@ -216,12 +216,6 @@ ia32_setup_arg_pages (struct linux_binpr
if (!mpnt)
return -ENOMEM;

- if (security_vm_enough_memory((IA32_STACK_TOP - (PAGE_MASK & (unsigned long) bprm->p))
- >> PAGE_SHIFT)) {
- kmem_cache_free(vm_area_cachep, mpnt);
- return -ENOMEM;
- }
-
memset(mpnt, 0, sizeof(*mpnt));

down_write(&current->mm->mmap_sem);
--- 2.6.14-rc1/arch/mips/kernel/sysirix.c 2005-09-13 15:22:15.000000000 +0100
+++ linux/arch/mips/kernel/sysirix.c 2005-09-13 18:51:43.000000000 +0100
@@ -581,18 +581,13 @@ asmlinkage int irix_brk(unsigned long br
}

/*
- * Check if we have enough memory..
+ * Ok, looks good - let it rip.
*/
- if (security_vm_enough_memory((newbrk-oldbrk) >> PAGE_SHIFT)) {
+ if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk) {
ret = -ENOMEM;
goto out;
}
-
- /*
- * Ok, looks good - let it rip.
- */
mm->brk = brk;
- do_brk(oldbrk, newbrk-oldbrk);
ret = 0;

out:
--- 2.6.14-rc1/arch/ppc64/kernel/vdso.c 2005-06-17 20:48:29.000000000 +0100
+++ linux/arch/ppc64/kernel/vdso.c 2005-09-13 20:50:02.000000000 +0100
@@ -224,10 +224,7 @@ int arch_setup_additional_pages(struct l
vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
if (vma == NULL)
return -ENOMEM;
- if (security_vm_enough_memory(vdso_pages)) {
- kmem_cache_free(vm_area_cachep, vma);
- return -ENOMEM;
- }
+
memset(vma, 0, sizeof(*vma));

/*
@@ -237,8 +234,10 @@ int arch_setup_additional_pages(struct l
*/
vdso_base = get_unmapped_area(NULL, vdso_base,
vdso_pages << PAGE_SHIFT, 0, 0);
- if (vdso_base & ~PAGE_MASK)
+ if (vdso_base & ~PAGE_MASK) {
+ kmem_cache_free(vm_area_cachep, vma);
return (int)vdso_base;
+ }

current->thread.vdso_base = vdso_base;

@@ -266,7 +265,11 @@ int arch_setup_additional_pages(struct l
vma->vm_ops = &vdso_vmops;

down_write(&mm->mmap_sem);
- insert_vm_struct(mm, vma);
+ if (insert_vm_struct(mm, vma)) {
+ up_write(&mm->mmap_sem);
+ kmem_cache_free(vm_area_cachep, vma);
+ return -ENOMEM;
+ }
mm->total_vm += (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
up_write(&mm->mmap_sem);

--- 2.6.14-rc1/arch/x86_64/ia32/ia32_binfmt.c 2005-08-29 00:41:01.000000000 +0100
+++ linux/arch/x86_64/ia32/ia32_binfmt.c 2005-09-13 18:05:20.000000000 +0100
@@ -353,11 +353,6 @@ int setup_arg_pages(struct linux_binprm
mpnt = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
if (!mpnt)
return -ENOMEM;
-
- if (security_vm_enough_memory((IA32_STACK_TOP - (PAGE_MASK & (unsigned long) bprm->p))>>PAGE_SHIFT)) {
- kmem_cache_free(vm_area_cachep, mpnt);
- return -ENOMEM;
- }

memset(mpnt, 0, sizeof(*mpnt));

--- 2.6.14-rc1/arch/x86_64/ia32/syscall32.c 2005-08-29 00:41:01.000000000 +0100
+++ linux/arch/x86_64/ia32/syscall32.c 2005-09-13 18:53:32.000000000 +0100
@@ -52,17 +52,13 @@ int syscall32_setup_pages(struct linux_b
vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
if (!vma)
return -ENOMEM;
- if (security_vm_enough_memory(npages)) {
- kmem_cache_free(vm_area_cachep, vma);
- return -ENOMEM;
- }

memset(vma, 0, sizeof(struct vm_area_struct));
/* Could randomize here */
vma->vm_start = VSYSCALL32_BASE;
vma->vm_end = VSYSCALL32_END;
/* MAYWRITE to allow gdb to COW and set breakpoints */
- vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYEXEC|VM_MAYWRITE;
+ vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYWRITE;
vma->vm_flags |= mm->def_flags;
vma->vm_page_prot = protection_map[vma->vm_flags & 7];
vma->vm_ops = &syscall32_vm_ops;
--- 2.6.14-rc1/fs/exec.c 2005-09-13 15:22:37.000000000 +0100
+++ linux/fs/exec.c 2005-09-13 17:50:46.000000000 +0100
@@ -421,11 +421,6 @@ int setup_arg_pages(struct linux_binprm
if (!mpnt)
return -ENOMEM;

- if (security_vm_enough_memory(arg_size >> PAGE_SHIFT)) {
- kmem_cache_free(vm_area_cachep, mpnt);
- return -ENOMEM;
- }
-
memset(mpnt, 0, sizeof(*mpnt));

down_write(&mm->mmap_sem);
--- 2.6.14-rc1/mm/mmap.c 2005-09-13 15:22:47.000000000 +0100
+++ linux/mm/mmap.c 2005-09-13 18:59:59.000000000 +0100
@@ -1993,6 +1993,9 @@ int insert_vm_struct(struct mm_struct *
__vma = find_vma_prepare(mm,vma->vm_start,&prev,&rb_link,&rb_parent);
if (__vma && __vma->vm_start < vma->vm_end)
return -ENOMEM;
+ if ((vma->vm_flags & VM_ACCOUNT) &&
+ security_vm_enough_memory(vma_pages(vma)))
+ return -ENOMEM;
vma_link(mm, vma, prev, rb_link, rb_parent);
return 0;
}
-
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