Validate the address before subtracting the channel base and use hwaddr 
for channel calculations to prevent unsigned underflow and truncation.

Resolves: Coverity CID 1685514

Reported-by: Alistair Francis <[email protected]>
Signed-off-by: Tao Ding <[email protected]>
---
Compared to patchv1, the modification of ch has been removed. 
Because ch is an unsigned int, it is sufficient.

 hw/dma/k230_gsdma.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/dma/k230_gsdma.c b/hw/dma/k230_gsdma.c
index 7635cd19e8..e422b436a2 100644
--- a/hw/dma/k230_gsdma.c
+++ b/hw/dma/k230_gsdma.c
@@ -329,6 +329,9 @@ static uint64_t k230_gsdma_read(void *opaque, hwaddr addr, 
unsigned int size)
         break;
     }
 
+    if (addr < K230_GSDMA_CH_BASE) {
+        goto out;
+    }
     ch = (addr - K230_GSDMA_CH_BASE) / K230_GSDMA_CH_STRIDE;
     ch_off = (addr - K230_GSDMA_CH_BASE) % K230_GSDMA_CH_STRIDE;
     if (ch < K230_GSDMA_NUM_SDMA_CHANNELS) {
@@ -355,6 +358,7 @@ static uint64_t k230_gsdma_read(void *opaque, hwaddr addr, 
unsigned int size)
         }
     }
 
+out:
     trace_k230_gsdma_read(addr, size, ret);
     return ret;
 }
-- 
2.43.0


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