4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Laura Abbott labbott@redhat.com
commit 45ad559a29629cb1c64ee636563c69b71524f077 upstream.
Syzbot reported yet another warning with Ion:
WARNING: CPU: 0 PID: 1467 at drivers/staging/android/ion/ion.c:122 ion_buffer_destroy+0xd4/0x190 drivers/staging/android/ion/ion.c:122 Kernel panic - not syncing: panic_on_warn set ...
This is catching that a buffer was freed with an existing kernel mapping still present. This can be easily be triggered from userspace by calling DMA_BUF_SYNC_START without calling DMA_BUF_SYNC_END. Switch to a single pr_warn_once to indicate the error without being disruptive.
Reported-by: syzbot+cd8bcd40cb049efa2770@syzkaller.appspotmail.com Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Laura Abbott labbott@redhat.com Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/staging/android/ion/ion.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/drivers/staging/android/ion/ion.c +++ b/drivers/staging/android/ion/ion.c @@ -192,8 +192,11 @@ err2:
void ion_buffer_destroy(struct ion_buffer *buffer) { - if (WARN_ON(buffer->kmap_cnt > 0)) + if (buffer->kmap_cnt > 0) { + pr_warn_once("%s: buffer still mapped in the kernel\n", + __func__); buffer->heap->ops->unmap_kernel(buffer->heap, buffer); + } buffer->heap->ops->free(buffer); vfree(buffer->pages); kfree(buffer);