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+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 41a647dfb738123023d56bc0174ba2477a0b0ea0..285a81e87ec853cef3c5c1a20400bfb35415a04b 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2157,6 +2157,15 @@ 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);
@@ -2173,7 +2182,7 @@ 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);
@@ -2991,12 +3000,16 @@ 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.
@@ -3005,7 +3018,7 @@ 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;
        }
 
        /*
@@ -3022,6 +3035,9 @@ 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)