[PATCH net] net: airoha: Add NULL check for of_reserved_mem_lookup() in airoha_qdma_init_hfwd_queues()

[ZhaoJinming]

of_reserved_mem_lookup() may return NULL if the reserved memory region
referenced by the "memory-region" phandle is not found in the reserved
memory table (e.g. due to a misconfigured DTS or a removed
memory-region node).  The current code dereferences the returned
pointer without checking for NULL, leading to a kernel NULL pointer
dereference at the following lines:

    dma_addr = rmem->base;                          // line 1156
    num_desc = div_u64(rmem->size, buf_size);       // line 1160

Add a NULL check after of_reserved_mem_lookup() and return -ENODEV if
the lookup fails, which is consistent with the existing error handling
for of_parse_phandle() failure in the same code block.

Fixes: 3a1ce9e3d01b ("net: airoha: Add the capability to allocate hwfd buffers via reserved-memory")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: ZhaoJinming<zhaojinming@xxxxxxxxxxxxx>
---
 drivers/net/ethernet/airoha/airoha_eth.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
index cecd66251dba..2444d3275a81 100644
--- a/drivers/net/ethernet/airoha/airoha_eth.c
+++ b/drivers/net/ethernet/airoha/airoha_eth.c
@@ -1153,6 +1153,9 @@ static int airoha_qdma_init_hfwd_queues(struct airoha_qdma *qdma)
 
 		rmem = of_reserved_mem_lookup(np);
 		of_node_put(np);
+		if (!rmem)
+			return -ENODEV;
+
 		dma_addr = rmem->base;
 		/* Compute the number of hw descriptors according to the
 		 * reserved memory size and the payload buffer size
-- 
2.25.1