[PATCH] ath10k: fix invalid dma_addr_t token assignment

From: Arnd Bergmann <arnd@arndb.de>

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>
---
 drivers/net/wireless/ath/ath10k/mac.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
index 7ca68c81d9b6..c0e78eaa65f8 100644
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c

@@ -5583,7 +5583,7 @@ 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;
+			arvif->beacon_paddr = DMA_MAPPING_ERROR;
 		} else {
 			arvif->beacon_buf =
 				dma_alloc_coherent(ar->dev,

-- 
2.29.2

On 14/10/2021 04:51, Arnd Bergmann wrote:

From: Arnd Bergmann <arnd@arndb.de>

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>

Reviewed-by: Fabio Estevam <redacted>

Arnd Bergmann [off-list ref] wrote:

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 <redacted>

Patch applied to ath-next branch of ath.git, thanks.

937e79c67740 ath10k: fix invalid dma_addr_t token assignment

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20211014075153.3655910-1-arnd@kernel.org/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches