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Old 07-05-2012, 09:40 PM
Brad Figg
 
Default hugetlb: fix resv_map leak in error path

Memory leak in mm/hugetlb.c in the Linux kernel before 3.4.2 allows local
users to cause a denial of service (memory consumption or system crash) via
invalid MAP_HUGETLB mmap operations.

Dave Hansen (1):
hugetlb: fix resv_map leak in error path

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

--
1.7.9.5


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Old 07-05-2012, 09:40 PM
Brad Figg
 
Default hugetlb: fix resv_map leak in error path

From: Dave Hansen <dave@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@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+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit c50ac050811d6485616a193eb0f37bfbd191cc89)
Signed-off-by: Brad Figg <brad.figg@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;
}

void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
--
1.7.9.5


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