[PATCH ath-next 1/2] wifi: ath12k: fix stride mismatch in mac_phy_caps_parse()

Currently, in ath12k_wmi_mac_phy_caps_parse(), kzalloc() sizes the
mac_phy_caps buffer as tot_phy_id * len, where len is clamped to
min(firmware_len, sizeof(struct ath12k_wmi_mac_phy_caps_params)). The
subsequent memcpy() destination advances by sizeof(full struct) per slot
via C pointer arithmetic, not by the clamped len. When firmware sends
short TLVs, the second and later slots are written past the end of the
allocation.

The reader in ath12k_pull_mac_phy_cap_svc_ready_ext() also indexes the
buffer with full-struct pointer arithmetic, so the allocation must match
that stride.

Fix by using kzalloc_objs(), which derives the element size from the
pointer type, making allocation size and pointer stride provably
consistent regardless of what len the firmware provides.

Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.1.c7-00108-QCAHMTSWPL_V1.0_V2.0_SILICONZ_UPSTREAM-3

Fixes: d889913205cf ("wifi: ath12k: driver for Qualcomm Wi-Fi 7 devices")
Assisted-by: Claude:claude-sonnet-4-6
Signed-off-by: Jeff Johnson <[email protected]>
---
 drivers/net/wireless/ath/ath12k/wmi.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/ath/ath12k/wmi.c b/drivers/net/wireless/ath/ath12k/wmi.c
index 672eae237ac6..d466baf5e90a 100644
--- a/drivers/net/wireless/ath/ath12k/wmi.c
+++ b/drivers/net/wireless/ath/ath12k/wmi.c
@@ -4765,14 +4765,16 @@ static int ath12k_wmi_mac_phy_caps_parse(struct ath12k_base *soc,
 	if (svc_rdy_ext->n_mac_phy_caps >= svc_rdy_ext->tot_phy_id)
 		return -ENOBUFS;
 
-	len = min_t(u16, len, sizeof(struct ath12k_wmi_mac_phy_caps_params));
 	if (!svc_rdy_ext->n_mac_phy_caps) {
-		svc_rdy_ext->mac_phy_caps = kzalloc((svc_rdy_ext->tot_phy_id) * len,
-						    GFP_ATOMIC);
+		svc_rdy_ext->mac_phy_caps =
+			kzalloc_objs(*svc_rdy_ext->mac_phy_caps,
+				     svc_rdy_ext->tot_phy_id,
+				     GFP_ATOMIC);
 		if (!svc_rdy_ext->mac_phy_caps)
 			return -ENOMEM;
 	}
 
+	len = min_t(u16, len, sizeof(struct ath12k_wmi_mac_phy_caps_params));
 	memcpy(svc_rdy_ext->mac_phy_caps + svc_rdy_ext->n_mac_phy_caps, ptr, len);
 	svc_rdy_ext->n_mac_phy_caps++;
 	return 0;

-- 
2.43.0