releases/4.17.2/staging-android-ion-switch-to-pr_warn_once-in-ion_buffer_destroy.patch

   1 From 45ad559a29629cb1c64ee636563c69b71524f077 Mon Sep 17 00:00:00 2001
   2 From: Laura Abbott <labbott@redhat.com>
   3 Date: Mon, 14 May 2018 14:35:09 -0700
   4 Subject: staging: android: ion: Switch to pr_warn_once in ion_buffer_destroy
   5
   6 From: Laura Abbott <labbott@redhat.com>
   7
   8 commit 45ad559a29629cb1c64ee636563c69b71524f077 upstream.
   9
  10 Syzbot reported yet another warning with Ion:
  11
  12 WARNING: CPU: 0 PID: 1467 at drivers/staging/android/ion/ion.c:122
  13 ion_buffer_destroy+0xd4/0x190 drivers/staging/android/ion/ion.c:122
  14 Kernel panic - not syncing: panic_on_warn set ...
  15
  16 This is catching that a buffer was freed with an existing kernel mapping
  17 still present. This can be easily be triggered from userspace by calling
  18 DMA_BUF_SYNC_START without calling DMA_BUF_SYNC_END. Switch to a single
  19 pr_warn_once to indicate the error without being disruptive.
  20
  21 Reported-by: syzbot+cd8bcd40cb049efa2770@syzkaller.appspotmail.com
  22 Reported-by: syzbot <syzkaller@googlegroups.com>
  23 Signed-off-by: Laura Abbott <labbott@redhat.com>
  24 Cc: stable <stable@vger.kernel.org>
  25 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  26
  27 ---
  28  drivers/staging/android/ion/ion.c |    5 ++++-
  29  1 file changed, 4 insertions(+), 1 deletion(-)
  30
  31 --- a/drivers/staging/android/ion/ion.c
  32 +++ b/drivers/staging/android/ion/ion.c
  33 @@ -114,8 +114,11 @@ err2:
  34
  35  void ion_buffer_destroy(struct ion_buffer *buffer)
  36  {
  37 -       if (WARN_ON(buffer->kmap_cnt > 0))
  38 +       if (buffer->kmap_cnt > 0) {
  39 +               pr_warn_once("%s: buffer still mapped in the kernel\n",
  40 +                            __func__);
  41                 buffer->heap->ops->unmap_kernel(buffer->heap, buffer);
  42 +       }
  43         buffer->heap->ops->free(buffer);
  44         kfree(buffer);
  45  }