[PATCH] hugetlb: fix resv_map leak in error path

[PATCH] hugetlb: fix resv_map leak in error path

[Dave Hansen]

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.

This hasn't been extensively tested.  Pretty much compile and
boot tested along with Christoph's test case:

	http://marc.info/?l=linux-mm&m=133728900729735

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
ecked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reported/tested-by: Christoph Lameter <cl@linux.com>

---

 linux-2.6.git-dave/mm/hugetlb.c |   28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff -puN mm/hugetlb.c~hugetlb-fix-leak mm/hugetlb.c
--- linux-2.6.git/mm/hugetlb.c~hugetlb-fix-leak	2012-05-21 13:24:38.369857759 -0700
+++ linux-2.6.git-dave/mm/hugetlb.c	2012-05-21 13:24:38.377857849 -0700
@@ -2157,6 +2157,15 @@ static void hugetlb_vm_op_open(struct vm
 		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);
@@ -2173,7 +2182,7 @@ static void hugetlb_vm_op_close(struct v
 		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);
@@ -2990,12 +2999,16 @@ int hugetlb_reserve_pages(struct 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.
@@ -3004,7 +3017,7 @@ int hugetlb_reserve_pages(struct inode *
 	ret = hugetlb_acct_memory(h, chg);
 	if (ret < 0) {
 		hugepage_subpool_put_pages(spool, chg);
-		return ret;
+		goto out_err;
 	}
 
 	/*
@@ -3021,6 +3034,9 @@ int hugetlb_reserve_pages(struct 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;
 }
 
 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
diff -puN Documentation/stable_kernel_rules.txt~hugetlb-fix-leak Documentation/stable_kernel_rules.txt
_

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Re: [PATCH] hugetlb: fix resv_map leak in error path

[KOSAKI Motohiro]

On 5/21/2012 4:28 PM, Dave Hansen wrote:
> 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.
> 
> This hasn't been extensively tested.  Pretty much compile and
> boot tested along with Christoph's test case:
> 
> 	http://marc.info/?l=linux-mm&m=133728900729735
> 
> Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
> Acked-by: Mel Gorman <mel@csn.ul.ie>
> ecked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

typo. ;-)

> Reported/tested-by: Christoph Lameter <cl@linux.com>

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Re: [PATCH] hugetlb: fix resv_map leak in error path

[Andrew Morton]

On Mon, 21 May 2012 13:28:14 -0700
Dave Hansen <dave@linux.vnet.ibm.com> wrote:

> 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.

How far back does this bug go?  The patch applies to 3.4 but gets
rejects in 3.3 and earlier.

> This hasn't been extensively tested.  Pretty much compile and
> boot tested along with Christoph's test case:
> 
> 	http://marc.info/?l=linux-mm&m=133728900729735

That isn't my favoritest ever changelog text :(

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Re: [PATCH] hugetlb: fix resv_map leak in error path

[Dave Hansen]

On 05/22/2012 01:45 PM, Andrew Morton wrote:
> On Mon, 21 May 2012 13:28:14 -0700
> Dave Hansen <dave@linux.vnet.ibm.com> wrote:
> 
>> 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.
> 
> How far back does this bug go?  The patch applies to 3.4 but gets
> rejects in 3.3 and earlier.

commit 17c9d12e126cb0de8d535dc1908c4819d712bc68
Date:   Wed Feb 11 16:34:16 2009 +0000

So, ~2.6.30.

I don't think it existed before that.  The code was there, but the
ordering made it OK.

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Re: [PATCH] hugetlb: fix resv_map leak in error path

[Christoph Lameter]

On Tue, 22 May 2012, Andrew Morton wrote:

> On Mon, 21 May 2012 13:28:14 -0700
> Dave Hansen <dave@linux.vnet.ibm.com> wrote:
>
> > 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.
>
> How far back does this bug go?  The patch applies to 3.4 but gets
> rejects in 3.3 and earlier.

The earliest that I have seen it on was 2.6.32. I have rediffed the patch
against 2.6.32 and 3.2.0.

----

Re: [PATCH] hugetlb: fix resv_map leak in error path

[Andrew Morton]

On Tue, 22 May 2012 16:05:02 -0500 (CDT)
Christoph Lameter <cl@linux.com> wrote:

> > How far back does this bug go?  The patch applies to 3.4 but gets
> > rejects in 3.3 and earlier.
> 
> The earliest that I have seen it on was 2.6.32. I have rediffed the patch
> against 2.6.32 and 3.2.0.

Great, thanks.  I did

: From: Dave Hansen <dave@linux.vnet.ibm.com>
: Subject: hugetlb: fix resv_map leak in error path
: 
: 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@linux.vnet.ibm.com>
: Acked-by: Mel Gorman <mel@csn.ul.ie>
: Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
: Reported-by: Christoph Lameter <cl@linux.com>
: Tested-by: Christoph Lameter <cl@linux.com>
: Cc: Andrea Arcangeli <aarcange@redhat.com>
: Cc: <stable@vger.kernel.org>	[2.6.32+]

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