From 5af10dfd0afc559bb4b0f7e3e8227a1578333995 Mon Sep 17 00:00:00 2001
From: Andrea Arcangeli <aarcange@redhat.com>
Date: Thu, 10 Aug 2017 15:23:38 -0700
Subject: [PATCH] userfaultfd: hugetlbfs: remove superfluous page unlock in
VM_SHARED case
Git-commit: 5af10dfd0afc559bb4b0f7e3e8227a1578333995
Patch-mainline: v4.13-rc5
References: bnc#1073113, CVE-2017-15127
huge_add_to_page_cache->add_to_page_cache implicitly unlocks the page
before returning in case of errors.
The error returned was -EEXIST by running UFFDIO_COPY on a non-hole
offset of a VM_SHARED hugetlbfs mapping. It was an userland bug that
triggered it and the kernel must cope with it returning -EEXIST from
ioctl(UFFDIO_COPY) as expected.
page dumped because: VM_BUG_ON_PAGE(!PageLocked(page))
kernel BUG at mm/filemap.c:964!
invalid opcode: 0000 [#1] SMP
CPU: 1 PID: 22582 Comm: qemu-system-x86 Not tainted 4.11.11-300.fc26.x86_64 #1
RIP: unlock_page+0x4a/0x50
Call Trace:
hugetlb_mcopy_atomic_pte+0xc0/0x320
mcopy_atomic+0x96f/0xbe0
userfaultfd_ioctl+0x218/0xe90
do_vfs_ioctl+0xa5/0x600
SyS_ioctl+0x79/0x90
entry_SYSCALL_64_fastpath+0x1a/0xa9
Link: http://lkml.kernel.org/r/20170802165145.22628-2-aarcange@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Tested-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Alexey Perevalov <a.perevalov@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
---
mm/hugetlb.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a1a0ac0ad6f6..31e207cb399b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4062,9 +4062,9 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
return ret;
out_release_unlock:
spin_unlock(ptl);
-out_release_nounlock:
if (vm_shared)
unlock_page(page);
+out_release_nounlock:
put_page(page);
goto out;
}
--
1.8.5.6