Home Home > GIT Browse
summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorHugh Dickins <hugh@veritas.com>2007-10-19 14:30:18 +0200
committerAdrian Bunk <bunk@kernel.org>2007-10-19 14:30:18 +0200
commitec2cb473e3bb0fe1538874cf7773638c235e5b45 (patch)
tree11c4be6cc3cae9c32c4932388d0945815262ccb6
parent79d2ce4bb1adf75b471824a13d2443748cb48db3 (diff)
hugetlb: fix prio_tree unit (CVE-2007-4133)
hugetlb_vmtruncate_list was misconverted to prio_tree: its prio_tree is in units of PAGE_SIZE (PAGE_CACHE_SIZE) like any other, not HPAGE_SIZE (whereas its radix_tree is kept in units of HPAGE_SIZE, otherwise slots would be absurdly sparse). At first I thought the error benign, just calling __unmap_hugepage_range on more vmas than necessary; but on 32-bit machines, when the prio_tree is searched correctly, it happens to ensure the v_offset calculation won't overflow. As it stood, when truncating at or beyond 4GB, it was liable to discard pages COWed from lower offsets; or even to clear pmd entries of preceding vmas, triggering exit_mmap's BUG_ON(nr_ptes). Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Adrian Bunk <bunk@kernel.org>
-rw-r--r--fs/hugetlbfs/inode.c24
1 files changed, 11 insertions, 13 deletions
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index b35195289945..ed8f5875e6af 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -310,26 +310,24 @@ static void hugetlbfs_drop_inode(struct inode *inode)
hugetlbfs_forget_inode(inode);
}
-/*
- * h_pgoff is in HPAGE_SIZE units.
- * vma->vm_pgoff is in PAGE_SIZE units.
- */
static inline void
-hugetlb_vmtruncate_list(struct prio_tree_root *root, unsigned long h_pgoff)
+hugetlb_vmtruncate_list(struct prio_tree_root *root, pgoff_t pgoff)
{
struct vm_area_struct *vma;
struct prio_tree_iter iter;
- vma_prio_tree_foreach(vma, &iter, root, h_pgoff, ULONG_MAX) {
- unsigned long h_vm_pgoff;
+ vma_prio_tree_foreach(vma, &iter, root, pgoff, ULONG_MAX) {
unsigned long v_offset;
- h_vm_pgoff = vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT);
- v_offset = (h_pgoff - h_vm_pgoff) << HPAGE_SHIFT;
/*
- * Is this VMA fully outside the truncation point?
+ * Can the expression below overflow on 32-bit arches?
+ * No, because the prio_tree returns us only those vmas
+ * which overlap the truncated area starting at pgoff,
+ * and no vma on a 32-bit arch can span beyond the 4GB.
*/
- if (h_vm_pgoff >= h_pgoff)
+ if (vma->vm_pgoff < pgoff)
+ v_offset = (pgoff - vma->vm_pgoff) << PAGE_SHIFT;
+ else
v_offset = 0;
unmap_hugepage_range(vma,
@@ -342,14 +340,14 @@ hugetlb_vmtruncate_list(struct prio_tree_root *root, unsigned long h_pgoff)
*/
static int hugetlb_vmtruncate(struct inode *inode, loff_t offset)
{
- unsigned long pgoff;
+ pgoff_t pgoff;
struct address_space *mapping = inode->i_mapping;
if (offset > inode->i_size)
return -EINVAL;
BUG_ON(offset & ~HPAGE_MASK);
- pgoff = offset >> HPAGE_SHIFT;
+ pgoff = offset >> PAGE_SHIFT;
inode->i_size = offset;
spin_lock(&mapping->i_mmap_lock);