[PATCH] [RESEND] gpu: ipu-v3: prg: avoid possible array underflow

[Arnd Bergmann]

gcc-8 reports that we access an array with a negative index
in an error case:

drivers/gpu/ipu-v3/ipu-prg.c: In function 'ipu_prg_channel_disable':
drivers/gpu/ipu-v3/ipu-prg.c:252:43: error: array subscript -22 is below array bounds of 'struct ipu_prg_channel[3]' [-Werror=array-bounds]

This moves the range check in front of the dereference.

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
----
Originally sent on Dec 4, 2017. No reply, so resending unchanged.
---
 drivers/gpu/ipu-v3/ipu-prg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/ipu-v3/ipu-prg.c b/drivers/gpu/ipu-v3/ipu-prg.c
index 067365c733c6..0bcb935e525c 100644
--- a/drivers/gpu/ipu-v3/ipu-prg.c
+++ b/drivers/gpu/ipu-v3/ipu-prg.c
@@ -250,7 +250,7 @@ void ipu_prg_channel_disable(struct ipuv3_channel *ipu_chan)
 	struct ipu_prg_channel *chan = &prg->chan[prg_chan];
 	u32 val;
 
-	if (!chan->enabled || prg_chan < 0)
+	if (prg_chan < 0 || !chan->enabled)
 		return;
 
 	pm_runtime_get_sync(prg->dev);
-- 
2.9.0