4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Laura Abbott <labbott@xxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
Signed-off-by: Laura Abbott <labbott@xxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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);
