[PATCH] VM/Security: add security hook to do_brk

[Eric Paris]

Given a specifically crafted binary do_brk() can be used to get low
pages available in userspace virtually memory and can thus be used to
circumvent the mmap_min_addr low memory protection. Add security checks
in do_brk().

Signed-off-by: Eric Paris <epa...@redhat.com>

---

mm/mmap.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/mm/mmap.c b/mm/mmap.c
index f4cfc6a..15678aa 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1941,6 +1941,10 @@ unsigned long do_brk(unsigned long addr, unsigned long len)
if (is_hugepage_only_range(mm, addr, len))
return -EINVAL;

+ error = security_file_mmap(0, 0, 0, 0, addr, 1);
+ if (error)
+ return error;
+
flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;

error = arch_mmap_check(addr, len, flags);

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[Alan Cox]

On Tue, Dec 04, 2007 at 11:06:55AM -0500, Eric Paris wrote:
> Given a specifically crafted binary do_brk() can be used to get low
> pages available in userspace virtually memory and can thus be used to
> circumvent the mmap_min_addr low memory protection. Add security checks
> in do_brk().
>
> Signed-off-by: Eric Paris <epa...@redhat.com>

ACK

[James Morris]

On Tue, 4 Dec 2007, Alan Cox wrote:

> On Tue, Dec 04, 2007 at 11:06:55AM -0500, Eric Paris wrote:
> > Given a specifically crafted binary do_brk() can be used to get low
> > pages available in userspace virtually memory and can thus be used to
> > circumvent the mmap_min_addr low memory protection. Add security checks
> > in do_brk().
> >
> > Signed-off-by: Eric Paris <epa...@redhat.com>
>
> ACK

Applied to
git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/selinux-2.6.git#for-akpm

--
James Morris
<jmo...@namei.org>