ath10k: fix invalid dma_addr_t token assignment

Using a kernel pointer in place of a dma_addr_t token can
lead to undefined behavior if that makes it into cache
management functions. The compiler caught one such attempt
in a cast:

drivers/net/wireless/ath/ath10k/mac.c: In function 'ath10k_add_interface':
drivers/net/wireless/ath/ath10k/mac.c:5586:47: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
 5586 |                         arvif->beacon_paddr = (dma_addr_t)arvif->beacon_buf;
      |                                               ^

Looking through how this gets used down the way, I'm fairly
sure that beacon_paddr is never accessed again for ATH10K_DEV_TYPE_HL
devices, and if it was accessed, that would be a bug.

Change the assignment to use a known-invalid address token
instead, which avoids the warning and makes it easier to catch
bugs if it does end up getting used.

Fixes: e263bdab9c0e ("ath10k: high latency fixes for beacon buffer")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211014075153.3655910-1-arnd@kernel.org

diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
index 5ec19d9..1f73fbf 100644 (file)
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -5583,7 +5583,15 @@ static int ath10k_add_interface(struct ieee80211_hw *hw,
                if (ar->bus_param.dev_type == ATH10K_DEV_TYPE_HL) {
                        arvif->beacon_buf = kmalloc(IEEE80211_MAX_FRAME_LEN,
                                                    GFP_KERNEL);
-                       arvif->beacon_paddr = (dma_addr_t)arvif->beacon_buf;
+
+                       /* Using a kernel pointer in place of a dma_addr_t
+                        * token can lead to undefined behavior if that
+                        * makes it into cache management functions. Use a
+                        * known-invalid address token instead, which
+                        * avoids the warning and makes it easier to catch
+                        * bugs if it does end up getting used.
+                        */
+                       arvif->beacon_paddr = DMA_MAPPING_ERROR;
                } else {
                        arvif->beacon_buf =
                                dma_alloc_coherent(ar->dev,