[ 30/82] hugetlb: fix resv_map leak in error path

Ben Hutchings
2012-06-08T05:07:52Z

From: Dave Hansen <dave@linux.vnet.ibm.com>

commit c50ac050811d6485616a193eb0f37bfbd191cc89 upstream.

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

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
[Christoph Lameter: I have rediffed the patch against 2.6.32 and 3.2.0.]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
mm/hugetlb.c | 28 ++++++++++++++++++++++------
1 file changed, 22 insertions(+), 6 deletions(-)

--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2068,6 +2068,15 @@
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 @@
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);
@@ -2884,12 +2893,16 @@
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.
@@ -2898,7 +2911,7 @@
ret = hugetlb_acct_memory(h, chg);
if (ret < 0) {
hugetlb_put_quota(inode->i_mapping, chg);
- return ret;
+ goto out_err;
}

/*
@@ -2915,6 +2928,9 @@
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)