[PATCH 1/1] [CVE-2012-2390] [LUCID] [NATTY] hugetlb: fix resv_map leak in error path

[Herton Ronaldo Krzesinski]

On Thu, Jul 05, 2012 at 02:40:33PM -0700, Brad Figg wrote:
> From: Dave Hansen <dave at linux.vnet.ibm.com>
> 
> CVE-2012-2390
> 
> BugLink: http://bugs.launchpad.net/bugs/1004621
> 
> When called for anonymous (non-shared) mappings, hugetlb_reserve_pages()
> does a resv_map_alloc().  It depends on code in hugetlbfs's
> vm_ops->close() to release that allocation.
> 
> However, in the mmap() failure path, we do a plain unmap_region() without
> the remove_vma() which actually calls vm_ops->close().
> 
> This is a decent fix.  This leak could get reintroduced if new code (say,
> after hugetlb_reserve_pages() in hugetlbfs_file_mmap()) decides to return
> an error.  But, I think it would have to unroll the reservation anyway.
> 
> Christoph's test case:
> 
> 	http://marc.info/?l=linux-mm&m=133728900729735
> 
> This patch applies to 3.4 and later.  A version for earlier kernels is at
> https://lkml.org/lkml/2012/5/22/418.
> 
> Signed-off-by: Dave Hansen <dave at linux.vnet.ibm.com>
> Acked-by: Mel Gorman <mel at csn.ul.ie>
> Acked-by: KOSAKI Motohiro <kosaki.motohiro at jp.fujitsu.com>
> Reported-by: Christoph Lameter <cl at linux.com>
> Tested-by: Christoph Lameter <cl at linux.com>
> Cc: Andrea Arcangeli <aarcange at redhat.com>
> Cc: <stable at vger.kernel.org>	[2.6.32+]
> Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
> (cherry picked from commit c50ac050811d6485616a193eb0f37bfbd191cc89)
> Signed-off-by: Brad Figg <brad.figg at canonical.com>
> ---
>  mm/hugetlb.c |   28 ++++++++++++++++++++++------
>  1 file changed, 22 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 20f9240..3d61035 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1772,6 +1772,15 @@ static void hugetlb_vm_op_open(struct vm_area_struct *vma)
>  		kref_get(&reservations->refs);
>  }
>  
> +static void resv_map_put(struct vm_area_struct *vma)
> +{
> +	struct resv_map *reservations = vma_resv_map(vma);
> +
> +	if (!reservations)
> +		return;
> +	kref_put(&reservations->refs, resv_map_release);
> +}
> +
>  static void hugetlb_vm_op_close(struct vm_area_struct *vma)
>  {
>  	struct hstate *h = hstate_vma(vma);
> @@ -1788,7 +1797,7 @@ static void hugetlb_vm_op_close(struct vm_area_struct *vma)
>  		reserve = (end - start) -
>  			region_count(&reservations->regions, start, end);
>  
> -		kref_put(&reservations->refs, resv_map_release);
> +		resv_map_put(vma);
>  
>  		if (reserve) {
>  			hugetlb_acct_memory(h, -reserve);
> @@ -2472,12 +2481,16 @@ int hugetlb_reserve_pages(struct inode *inode,
>  		set_vma_resv_flags(vma, HPAGE_RESV_OWNER);
>  	}
>  
> -	if (chg < 0)
> -		return chg;
> +	if (chg < 0) {
> +		ret = chg;
> +		goto out_err;
> +	}
>  
>  	/* There must be enough pages in the subpool for the mapping */
> -	if (hugepage_subpool_get_pages(spool, chg))
> -		return -ENOSPC;
> +	if (hugepage_subpool_get_pages(spool, chg)) {
> +		ret = -ENOSPC;
> +		goto out_err;
> +	}
>  
>  	/*
>  	 * Check enough hugepages are available for the reservation.
> @@ -2486,7 +2499,7 @@ int hugetlb_reserve_pages(struct inode *inode,
>  	ret = hugetlb_acct_memory(h, chg);
>  	if (ret < 0) {
>  		hugepage_subpool_put_pages(spool, chg);
> -		return ret;
> +		goto out_err;
>  	}
>  
>  	/*
> @@ -2503,6 +2516,9 @@ int hugetlb_reserve_pages(struct inode *inode,
>  	if (!vma || vma->vm_flags & VM_MAYSHARE)
>  		region_add(&inode->i_mapping->private_list, from, to);
>  	return 0;
> +out_err:
> +	resv_map_put(vma);
> +	return ret;

Looks like we have also have to pick 4523e1458566a0e8ecfaff90f380dd23acc44d27
on top after applying this, to avoid issues here.

>  }
>  
>  void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
> -- 
> 1.7.9.5
> 
> 
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-- 
[]'s
Herton