This is a note to let you know that I've just added the patch titled
userfaultfd: hugetlbfs: prevent UFFDIO_COPY to fill beyond the end of i_size
to the 4.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
userfaultfd-hugetlbfs-prevent-uffdio_copy-to-fill-beyond-the-end-of-i_size.patch
and it can be found in the queue-4.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1e3921471354244f70fe268586ff94a97a6dd4df Mon Sep 17 00:00:00 2001
From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Date: Thu, 2 Nov 2017 15:59:29 -0700
Subject: userfaultfd: hugetlbfs: prevent UFFDIO_COPY to fill beyond the end of i_size
From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
commit 1e3921471354244f70fe268586ff94a97a6dd4df upstream.
This oops:
kernel BUG at fs/hugetlbfs/inode.c:484!
RIP: remove_inode_hugepages+0x3d0/0x410
Call Trace:
hugetlbfs_setattr+0xd9/0x130
notify_change+0x292/0x410
do_truncate+0x65/0xa0
do_sys_ftruncate.constprop.3+0x11a/0x180
SyS_ftruncate+0xe/0x10
tracesys+0xd9/0xde
was caused by the lack of i_size check in hugetlb_mcopy_atomic_pte.
mmap() can still succeed beyond the end of the i_size after vmtruncate
zapped vmas in those ranges, but the faults must not succeed, and that
includes UFFDIO_COPY.
We could differentiate the retval to userland to represent a SIGBUS like
a page fault would do (vs SIGSEGV), but it doesn't seem very useful and
we'd need to pick a random retval as there's no meaningful syscall
retval that would differentiate from SIGSEGV and SIGBUS, there's just
-EFAULT.
Link: http://lkml.kernel.org/r/20171016223914.2421-2-aarcange@xxxxxxxxxx
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Cc: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 32 ++++++++++++++++++++++++++++++--
1 file changed, 30 insertions(+), 2 deletions(-)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3977,6 +3977,9 @@ int hugetlb_mcopy_atomic_pte(struct mm_s
unsigned long src_addr,
struct page **pagep)
{
+ struct address_space *mapping;
+ pgoff_t idx;
+ unsigned long size;
int vm_shared = dst_vma->vm_flags & VM_SHARED;
struct hstate *h = hstate_vma(dst_vma);
pte_t _dst_pte;
@@ -4014,13 +4017,24 @@ int hugetlb_mcopy_atomic_pte(struct mm_s
__SetPageUptodate(page);
set_page_huge_active(page);
+ mapping = dst_vma->vm_file->f_mapping;
+ idx = vma_hugecache_offset(h, dst_vma, dst_addr);
+
/*
* If shared, add to page cache
*/
if (vm_shared) {
- struct address_space *mapping = dst_vma->vm_file->f_mapping;
- pgoff_t idx = vma_hugecache_offset(h, dst_vma, dst_addr);
+ size = i_size_read(mapping->host) >> huge_page_shift(h);
+ ret = -EFAULT;
+ if (idx >= size)
+ goto out_release_nounlock;
+ /*
+ * Serialization between remove_inode_hugepages() and
+ * huge_add_to_page_cache() below happens through the
+ * hugetlb_fault_mutex_table that here must be hold by
+ * the caller.
+ */
ret = huge_add_to_page_cache(page, mapping, idx);
if (ret)
goto out_release_nounlock;
@@ -4029,6 +4043,20 @@ int hugetlb_mcopy_atomic_pte(struct mm_s
ptl = huge_pte_lockptr(h, dst_mm, dst_pte);
spin_lock(ptl);
+ /*
+ * Recheck the i_size after holding PT lock to make sure not
+ * to leave any page mapped (as page_mapped()) beyond the end
+ * of the i_size (remove_inode_hugepages() is strict about
+ * enforcing that). If we bail out here, we'll also leave a
+ * page in the radix tree in the vm_shared case beyond the end
+ * of the i_size, but remove_inode_hugepages() will take care
+ * of it as soon as we drop the hugetlb_fault_mutex_table.
+ */
+ size = i_size_read(mapping->host) >> huge_page_shift(h);
+ ret = -EFAULT;
+ if (idx >= size)
+ goto out_release_unlock;
+
ret = -EEXIST;
if (!huge_pte_none(huge_ptep_get(dst_pte)))
goto out_release_unlock;
Patches currently in stable-queue which might be from aarcange@xxxxxxxxxx are
queue-4.13/userfaultfd-hugetlbfs-prevent-uffdio_copy-to-fill-beyond-the-end-of-i_size.patch