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authorMike Kravetz <mike.kravetz@oracle.com>2022-10-19 22:19:57 +0200
committerAndrew Morton <akpm@linux-foundation.org>2022-10-21 06:27:23 +0200
commit612b8a317023e1396965aacac43d80053c6e77db (patch)
tree6009fbe6327fcd61f17138200213ae696a4fe965 /mm/hugetlb.c
parentmm/page_alloc: reduce potential fragmentation in make_alloc_exact() (diff)
downloadlinux-612b8a317023e1396965aacac43d80053c6e77db.tar.xz
linux-612b8a317023e1396965aacac43d80053c6e77db.zip
hugetlb: fix memory leak associated with vma_lock structure
The hugetlb vma_lock structure hangs off the vm_private_data pointer of sharable hugetlb vmas. The structure is vma specific and can not be shared between vmas. At fork and various other times, vmas are duplicated via vm_area_dup(). When this happens, the pointer in the newly created vma must be cleared and the structure reallocated. Two hugetlb specific routines deal with this hugetlb_dup_vma_private and hugetlb_vm_op_open. Both routines are called for newly created vmas. hugetlb_dup_vma_private would always clear the pointer and hugetlb_vm_op_open would allocate the new vms_lock structure. This did not work in the case of this calling sequence pointed out in [1]. move_vma copy_vma new_vma = vm_area_dup(vma); new_vma->vm_ops->open(new_vma); --> new_vma has its own vma lock. is_vm_hugetlb_page(vma) clear_vma_resv_huge_pages hugetlb_dup_vma_private --> vma->vm_private_data is set to NULL When clearing hugetlb_dup_vma_private we actually leak the associated vma_lock structure. The vma_lock structure contains a pointer to the associated vma. This information can be used in hugetlb_dup_vma_private and hugetlb_vm_op_open to ensure we only clear the vm_private_data of newly created (copied) vmas. In such cases, the vma->vma_lock->vma field will not point to the vma. Update hugetlb_dup_vma_private and hugetlb_vm_op_open to not clear vm_private_data if vma->vma_lock->vma == vma. Also, log a warning if hugetlb_vm_op_open ever encounters the case where vma_lock has already been correctly allocated for the vma. [1] https://lore.kernel.org/linux-mm/5154292a-4c55-28cd-0935-82441e512fc3@huawei.com/ Link: https://lkml.kernel.org/r/20221019201957.34607-1-mike.kravetz@oracle.com Fixes: 131a79b474e9 ("hugetlb: fix vma lock handling during split vma and range unmapping") Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: James Houghton <jthoughton@google.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mina Almasry <almasrymina@google.com> Cc: Muchun Song <songmuchun@bytedance.com> Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Prakash Sangappa <prakash.sangappa@oracle.com> Cc: Sven Schnelle <svens@linux.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to '')
-rw-r--r--mm/hugetlb.c35
1 files changed, 27 insertions, 8 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index dede0337c07c..546df97c31e4 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1014,15 +1014,23 @@ void hugetlb_dup_vma_private(struct vm_area_struct *vma)
VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
/*
* Clear vm_private_data
+ * - For shared mappings this is a per-vma semaphore that may be
+ * allocated in a subsequent call to hugetlb_vm_op_open.
+ * Before clearing, make sure pointer is not associated with vma
+ * as this will leak the structure. This is the case when called
+ * via clear_vma_resv_huge_pages() and hugetlb_vm_op_open has already
+ * been called to allocate a new structure.
* - For MAP_PRIVATE mappings, this is the reserve map which does
* not apply to children. Faults generated by the children are
* not guaranteed to succeed, even if read-only.
- * - For shared mappings this is a per-vma semaphore that may be
- * allocated in a subsequent call to hugetlb_vm_op_open.
*/
- vma->vm_private_data = (void *)0;
- if (!(vma->vm_flags & VM_MAYSHARE))
- return;
+ if (vma->vm_flags & VM_MAYSHARE) {
+ struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
+
+ if (vma_lock && vma_lock->vma != vma)
+ vma->vm_private_data = NULL;
+ } else
+ vma->vm_private_data = NULL;
}
/*
@@ -4601,6 +4609,7 @@ static void hugetlb_vm_op_open(struct vm_area_struct *vma)
struct resv_map *resv = vma_resv_map(vma);
/*
+ * HPAGE_RESV_OWNER indicates a private mapping.
* This new VMA should share its siblings reservation map if present.
* The VMA will only ever have a valid reservation map pointer where
* it is being copied for another still existing VMA. As that VMA
@@ -4615,11 +4624,21 @@ static void hugetlb_vm_op_open(struct vm_area_struct *vma)
/*
* vma_lock structure for sharable mappings is vma specific.
- * Clear old pointer (if copied via vm_area_dup) and create new.
+ * Clear old pointer (if copied via vm_area_dup) and allocate
+ * new structure. Before clearing, make sure vma_lock is not
+ * for this vma.
*/
if (vma->vm_flags & VM_MAYSHARE) {
- vma->vm_private_data = NULL;
- hugetlb_vma_lock_alloc(vma);
+ struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
+
+ if (vma_lock) {
+ if (vma_lock->vma != vma) {
+ vma->vm_private_data = NULL;
+ hugetlb_vma_lock_alloc(vma);
+ } else
+ pr_warn("HugeTLB: vma_lock already exists in %s.\n", __func__);
+ } else
+ hugetlb_vma_lock_alloc(vma);
}
}