APPLIED [CVE-2010-4346 Karmic] install_special_mapping skips security_file_mmap check. CVE-2010-4346

[Steve Conklin]

On Thu, 2011-03-10 at 12:13 +0000, Brad Figg wrote:
> On 03/10/2011 10:51 AM, Steve Conklin wrote:
> > From: Tavis Ormandy<taviso at cmpxchg8b.com>
> >
> > BugLink: http://bugs.launchpad.net/bugs/731971
> >
> > CVE-2010-4346
> >
> > The install_special_mapping routine (used, for example, to setup the
> > vdso) skips the security check before insert_vm_struct, allowing a local
> > attacker to bypass the mmap_min_addr security restriction by limiting
> > the available pages for special mappings.
> >
> > bprm_mm_init() also skips the check, and although I don't think this can
> > be used to bypass any restrictions, I don't see any reason not to have
> > the security check.
> >
> >    $ uname -m
> >    x86_64
> >    $ cat /proc/sys/vm/mmap_min_addr
> >    65536
> >    $ cat install_special_mapping.s
> >    section .bss
> >        resb BSS_SIZE
> >    section .text
> >        global _start
> >        _start:
> >            mov     eax, __NR_pause
> >            int     0x80
> >    $ nasm -D__NR_pause=29 -DBSS_SIZE=0xfffed000 -f elf -o install_special_mapping.o install_special_mapping.s
> >    $ ld -m elf_i386 -Ttext=0x10000 -Tbss=0x11000 -o install_special_mapping install_special_mapping.o
> >    $ ./install_special_mapping&
> >    [1] 14303
> >    $ cat /proc/14303/maps
> >    0000f000-00010000 r-xp 00000000 00:00 0                                  [vdso]
> >    00010000-00011000 r-xp 00001000 00:19 2453665                            /home/taviso/install_special_mapping
> >    00011000-ffffe000 rwxp 00000000 00:00 0                                  [stack]
> >
> > It's worth noting that Red Hat are shipping with mmap_min_addr set to
> > 4096.
> >
> > Signed-off-by: Tavis Ormandy<taviso at google.com>
> > Acked-by: Kees Cook<kees at ubuntu.com>
> > Acked-by: Robert Swiecki<swiecki at google.com>
> > [ Changed to not drop the error code - akpm ]
> > Reviewed-by: James Morris<jmorris at namei.org>
> > Signed-off-by: Linus Torvalds<torvalds at linux-foundation.org>
> > backported from upstream commit 462e635e5b73ba9a4c03913b77138cd57ce4b050
> > Signed-off-by: Steve Conklin<sconklin at canonical.com>
> > ---
> >   fs/exec.c |    5 +++++
> >   mm/mmap.c |   16 ++++++++++++----
> >   2 files changed, 17 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/exec.c b/fs/exec.c
> > index 1bedd94..9cf5fb5 100644
> > --- a/fs/exec.c
> > +++ b/fs/exec.c
> > @@ -247,6 +247,11 @@ static int __bprm_mm_init(struct linux_binprm *bprm)
> >   	vma->vm_start = vma->vm_end - PAGE_SIZE;
> >   	vma->vm_flags = VM_STACK_FLAGS;
> >   	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
> > +
> > +	err = security_file_mmap(NULL, 0, 0, 0, vma->vm_start, 1);
> > +	if (err)
> > +		goto err;
> > +
> >   	err = insert_vm_struct(mm, vma);
> >   	if (err)
> >   		goto err;
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index ac9cceb..a53ad79 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -2390,6 +2390,7 @@ int install_special_mapping(struct mm_struct *mm,
> >   			    unsigned long addr, unsigned long len,
> >   			    unsigned long vm_flags, struct page **pages)
> >   {
> > +	int ret;
> >   	struct vm_area_struct *vma;
> >
> >   	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
> > @@ -2406,16 +2407,23 @@ int install_special_mapping(struct mm_struct *mm,
> >   	vma->vm_ops =&special_mapping_vmops;
> >   	vma->vm_private_data = pages;
> >
> > -	if (unlikely(insert_vm_struct(mm, vma))) {
> > -		kmem_cache_free(vm_area_cachep, vma);
> > -		return -ENOMEM;
> > -	}
> > +	ret = security_file_mmap(NULL, 0, 0, 0, vma->vm_start, 1);
> > +	if (ret)
> > +		goto out;
> > +
> > +	ret = insert_vm_struct(mm, vma);
> > +	if (ret)
> > +		goto out;
> >
> >   	mm->total_vm += len>>  PAGE_SHIFT;
> >
> >   	perf_counter_mmap(vma);
> >
> >   	return 0;
> > +
> > +out:
> > +	kmem_cache_free(vm_area_cachep, vma);
> > +	return ret;
> >   }
> >
> >   static DEFINE_MUTEX(mm_all_locks_mutex);
> 
> Acked-by: Brad Figg <brad.figg at canonical.com>
> 
> -- 
> Brad Figg brad.figg at canonical.com http://www.canonical.com
> 

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