On Wed, Jul 11, 2018 at 02:04:49PM -0700, Andrew Morton wrote:
> On Wed, 11 Jul 2018 09:49:01 -0700 syzbot
> <syzbot+120abb1c3f7bfdc52...@syzkaller.appspotmail.com> wrote:
>
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit: 98be45067040 Add linux-next specific files for 20180711
> > git tree: linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=12496ac2400000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=3f3b3673fec35d01
> > dashboard link: https://syzkaller.appspot.com/bug?extid=120abb1c3f7bfdc523f7
> > compiler: gcc (GCC) 8.0.1 20180413 (experimental)
> > syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=12a46568400000
>
> Handy. /dev/ion from drivers/staging/android/ion/ion.c
>
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+120abb1c3f7bfdc52...@syzkaller.appspotmail.com
> >
> > R10: 0000000004000812 R11: 0000000000000246 R12: 0000000000000005
> > R13: 00000000004c0565 R14: 00000000004cffb0 R15: 0000000000000005
> > ion_mmap: failure mapping buffer to userspace
> > kasan: CONFIG_KASAN_INLINE enabled
> > kasan: GPF could be caused by NULL-ptr deref or user memory access
> > general protection fault: 0000 [#1] SMP KASAN
> > CPU: 0 PID: 4785 Comm: syz-executor0 Not tainted 4.18.0-rc4-next-20180711+
> > #4
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > RIP: 0010:_vm_normal_page+0x1e5/0x330 mm/memory.c:828
>
> Presumably has a NULL vma->vm_ops. Probably one of the now-removed
> checks in mm-drop-unneeded-vm_ops-checks.patch would have avoided
> this.
>
> Something for Kirill to think about ;)
>
Okay. Looks like we need vm_ops in the error path too :P
Here's the fixup which should help.
I'll post the new version of the patchset once figure out nommu issues.
diff --git a/mm/mmap.c b/mm/mmap.c
index 74d4d2a8fe08..eedac20735c1 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1776,6 +1776,11 @@ unsigned long mmap_region(struct file *file, unsigned
long addr,
*/
vma->vm_file = get_file(file);
error = call_mmap(file, vma);
+
+ /* All mappings must have ->vm_ops set */
+ if (!vma->vm_ops)
+ vma->vm_ops = &dummy_vm_ops;
+
if (error)
goto unmap_and_free_vma;
@@ -1788,10 +1793,6 @@ unsigned long mmap_region(struct file *file, unsigned
long addr,
*/
WARN_ON_ONCE(addr != vma->vm_start);
- /* All mappings must have ->vm_ops set */
- if (!vma->vm_ops)
- vma->vm_ops = &dummy_vm_ops;
-
addr = vma->vm_start;
vm_flags = vma->vm_flags;
} else if (vm_flags & VM_SHARED) {
--
Kirill A. Shutemov
