drm/msm: Ensure that the hardware write pointer is valid
[ Upstream commit 88b333b0ed790f9433ff542b163bf972953b74d3 ]
Currently the value written to CP_RB_WPTR is calculated on the fly as
(rb->next - rb->start). But as the code is designed rb->next is wrapped
before writing the commands so if a series of commands happened to
fit perfectly in the ringbuffer, rb->next would end up being equal to
rb->size / 4 and thus result in an out of bounds address to CP_RB_WPTR.
The easiest way to fix this is to mask WPTR when writing it to the
hardware; it makes the hardware happy and the rest of the ringbuffer
math appears to work and there isn't any point in upsetting anything.
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
[squash in is_power_of_2() check]
Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/gpu/drm/msm/msm_ringbuffer.c b/drivers/gpu/drm/msm/msm_ringbuffer.c
index f326cf6..67b34e0 100644
--- a/drivers/gpu/drm/msm/msm_ringbuffer.c
+++ b/drivers/gpu/drm/msm/msm_ringbuffer.c
@@ -23,7 +23,8 @@
struct msm_ringbuffer *ring;
int ret;
- size = ALIGN(size, 4); /* size should be dword aligned */
+ if (WARN_ON(!is_power_of_2(size)))
+ return ERR_PTR(-EINVAL);
ring = kzalloc(sizeof(*ring), GFP_KERNEL);
if (!ring) {