On Tue, 22 May 2012, Andrew Morton wrote:
> On Mon, 21 May 2012 13:28:14 -0700
> Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> 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.
----
>From dave@xxxxxxxxxxxxxxxxxx Fri May 18 13:50:17 2012
Date: Fri, 18 May 2012 11:46:30 -0700
From: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
To: cl@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, aarcange@xxxxxxxxxx, kosaki.motohiro@xxxxxxxxxxxxxx, hughd@xxxxxxxxxx, rientjes@xxxxxxxxxx, adobriyan@xxxxxxxxx, akpm@xxxxxxxxxxxxxxxxxxxx, mel@xxxxxxxxx, Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
Subject: [RFC][PATCH] 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.
This hasn't been extensively tested. Pretty much compile and
boot tested along with Christoph's test case.
Comments?
Signed-off-by: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 28 ++++++++++++++++++++++------
1 file changed, 22 insertions(+), 6 deletions(-)
Index: linux-3.2.0/mm/hugetlb.c
===================================================================
--- linux-3.2.0.orig/mm/hugetlb.c 2012-01-04 17:55:44.000000000 -0600
+++ linux-3.2.0/mm/hugetlb.c 2012-05-22 03:32:37.760054550 -0500
@@ -2068,6 +2068,15 @@ 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);
@@ -2083,7 +2092,7 @@ 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);
@@ -2883,12 +2892,16 @@ 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 filesystem quota for the mapping */
- if (hugetlb_get_quota(inode->i_mapping, chg))
- return -ENOSPC;
+ if (hugetlb_get_quota(inode->i_mapping, chg)) {
+ ret = -ENOSPC;
+ goto out_err;
+ }
/*
* Check enough hugepages are available for the reservation.
@@ -2897,7 +2910,7 @@ int hugetlb_reserve_pages(struct inode *
ret = hugetlb_acct_memory(h, chg);
if (ret < 0) {
hugetlb_put_quota(inode->i_mapping, chg);
- return ret;
+ goto out_err;
}
/*
@@ -2914,6 +2927,9 @@ 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)
--
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