[PATCH] error path in setup_arg_pages() misses vm_unacct_memory()

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>
Signed-Off-By: Kirill Korotaev <dev@sw.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 9 insertions, 6 deletions

diff --git a/arch/ppc64/kernel/vdso.c b/arch/ppc64/kernel/vdso.c
index 4777676365fe..efa985f05aca 100644
--- a/arch/ppc64/kernel/vdso.c
+++ b/arch/ppc64/kernel/vdso.c
@@ -224,10 +224,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int executable_stack)
         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 linux_binprm *bprm, int executable_stack)
          */
         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 linux_binprm *bprm, int executable_stack)
         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);