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 <mitchelh@xxxxxxxxxxxxxx>
---
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 3d5bf14722..f55f61a4cc 100644
--- a/drivers/staging/android/ion/ion.c
+++ b/drivers/staging/android/ion/ion.c
@@ -626,6 +626,10 @@ 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);
--
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