From 22f6b9789aef2e0b0b409b1d7708cc653540248c Mon Sep 17 00:00:00 2001 From: Mitchel Humpherys Date: Fri, 23 May 2014 13:01:22 -0700 Subject: [PATCH] staging: ion: WARN when the handle kmap_cnt is going to wrap around There are certain client bugs (double unmap, for example) that can cause the handle->kmap_cnt (an unsigned int) to wrap around from zero. This causes problems when the handle is destroyed because we have: while (handle->kmap_cnt) ion_handle_kmap_put(handle); which takes a long time to complete when kmap_cnt starts at ~0 and can result in a watchdog timeout. WARN and bail when kmap_cnt is about to wrap around from zero. Signed-off-by: Mitchel Humpherys Acked-by: Colin Cross Signed-off-by: Greg Kroah-Hartman --- drivers/staging/android/ion/ion.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c index ea2c8a9..389b8f6 100644 --- a/drivers/staging/android/ion/ion.c +++ b/drivers/staging/android/ion/ion.c @@ -627,6 +627,10 @@ static void ion_handle_kmap_put(struct ion_handle *handle) { struct ion_buffer *buffer = handle->buffer; + if (!handle->kmap_cnt) { + WARN(1, "%s: Double unmap detected! bailing...\n", __func__); + return; + } handle->kmap_cnt--; if (!handle->kmap_cnt) ion_buffer_kmap_put(buffer); -- 2.7.4