[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>

7 files changed, 15 insertions, 34 deletions

diff --git a/arch/ia64/ia32/binfmt_elf32.c b/arch/ia64/ia32/binfmt_elf32.c
index 31de70b7c67f..a7280d9f6c16 100644
--- a/arch/ia64/ia32/binfmt_elf32.c
+++ b/arch/ia64/ia32/binfmt_elf32.c
@@ -216,12 +216,6 @@ ia32_setup_arg_pages (struct linux_binprm *bprm, int executable_stack)
         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);
diff --git a/arch/mips/kernel/sysirix.c b/arch/mips/kernel/sysirix.c
index 4de155699c4f..7ae4af476974 100644
--- a/arch/mips/kernel/sysirix.c
+++ b/arch/mips/kernel/sysirix.c
@@ -581,18 +581,13 @@ asmlinkage int irix_brk(unsigned long brk)
         }
 
         /*
-         * 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:
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);
 
diff --git a/arch/x86_64/ia32/ia32_binfmt.c b/arch/x86_64/ia32/ia32_binfmt.c
index c8131f342cfc..d9161e395978 100644
--- a/arch/x86_64/ia32/ia32_binfmt.c
+++ b/arch/x86_64/ia32/ia32_binfmt.c
@@ -353,11 +353,6 @@ int setup_arg_pages(struct linux_binprm *bprm, unsigned long stack_top, int exec
         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));
 
diff --git a/arch/x86_64/ia32/syscall32.c b/arch/x86_64/ia32/syscall32.c
index adbc5f8089e9..3a01329473ab 100644
--- a/arch/x86_64/ia32/syscall32.c
+++ b/arch/x86_64/ia32/syscall32.c
@@ -52,17 +52,13 @@ int syscall32_setup_pages(struct linux_binprm *bprm, int exstack)
         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;
diff --git a/fs/exec.c b/fs/exec.c
index 6fae59a22b43..a04a575ad433 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -421,11 +421,6 @@ int setup_arg_pages(struct linux_binprm *bprm,
         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);
diff --git a/mm/mmap.c b/mm/mmap.c
index 12334aecf8ad..8b8e05f07cdb 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1993,6 +1993,9 @@ int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
         __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;
 }