[PATCH linux-4.9.y] dmaengine: dmatest: warn user when dma test times out

[Adam Wallis <awallis@codeaurora.org>]

From: Adam Wallis <awallis@codeaurora.org>

commit a9df21e34b422f79d9a9fa5c3eff8c2a53491be6 upstream.

This patch was backported and only needed a line adjustment.

Commit adfa543e7314 ("dmatest: don't use set_freezable_with_signal()")
introduced a bug (that is in fact documented by the patch commit text)
that leaves behind a dangling pointer. Since the done_wait structure is
allocated on the stack, future invocations to the DMATEST can produce
undesirable results (e.g., corrupted spinlocks). Ideally, this would be
cleaned up in the thread handler, but at the very least, the kernel
is left in a very precarious scenario that can lead to some long debug
sessions when the crash comes later.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=197605
Signed-off-by: Adam Wallis <awallis@codeaurora.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
---
 drivers/dma/dmatest.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
index cf76fc6..fbb7551 100644
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -666,6 +666,7 @@ static int dmatest_func(void *data)
 			 * free it this time?" dancing.  For now, just
 			 * leave it dangling.
 			 */
+			WARN(1, "dmatest: Kernel stack may be corrupted!!\n");
 			dmaengine_unmap_put(um);
 			result("test timed out", total_tests, src_off, dst_off,
 			       len, 0);
-- 
Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.