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

Stefan Bader stefan.bader at canonical.com
Thu Mar 10 09:39:41 UTC 2011


On 03/09/2011 03:25 PM, 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 |    7 +++++++
>  mm/mmap.c |   16 ++++++++++++----
>  2 files changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/exec.c b/fs/exec.c
> index 1bedd94..a13f815 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -247,6 +247,13 @@ 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);
> +

> +	INIT_LIST_HEAD(&vma->anon_vma_chain);

I think thats actually wrong

> +
> +	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);




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