On Wed, Jul 11, 2018 at 02:04:49PM -0700, Andrew Morton wrote: > On Wed, 11 Jul 2018 09:49:01 -0700 syzbot <syzbot+120abb1c3f7bfdc523f7@xxxxxxxxxxxxxxxxxxxxxxxxx> 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+120abb1c3f7bfdc523f7@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > 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
