From: Hari Chandrakanthan quic_haric@quicinc.com
[ Upstream commit 2826139f9295821fe2b049318a1cc057ec003131 ]
Currently, the link_valid field is not initialized in the monitor Rx path. This can result in random values for the link_valid and link_id leads to undefined behaviour in mac80211. Therefore, initialize the link_valid field in the monitor Rx path.
Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.3.1-00173-QCAHKSWPL_SILICONZ-1 Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3
Signed-off-by: Hari Chandrakanthan quic_haric@quicinc.com Tested-by: Nicolas Escande nico.escande@gmail.com Reviewed-by: Vasanthakumar Thiagarajan vasanthakumar.thiagarajan@oss.qualcomm.com Signed-off-by: Karthikeyan Periyasamy quic_periyasa@quicinc.com Link: https://patch.msgid.link/20250324062518.2752822-2-quic_periyasa@quicinc.com Signed-off-by: Jeff Johnson jeff.johnson@oss.qualcomm.com Signed-off-by: Sasha Levin sashal@kernel.org ---
Based on my analysis of the commit and the code context, here is my assessment: **YES** This commit should be backported to stable kernel trees. Here's my extensive analysis: ## Technical Analysis **Code Change Impact:** The commit adds a single line `status->link_valid = 0;` at the beginning of the `ath12k_dp_mon_rx_deliver_msdu()` function in the monitor Rx path. This initializes the `link_valid` field in the `ieee80211_rx_status` structure before any subsequent processing. **Root Cause and Problem:** 1. **Uninitialized Memory Issue**: The `ieee80211_rx_status` structure contains the `link_valid` field (1 bit) and `link_id` field (4 bits) that were not being initialized in the monitor Rx path. 2. **Undefined Behavior**: Without initialization, these fields contain random stack memory values, which can cause unpredictable behavior in mac80211 when it processes received frames. 3. **MLO Context**: The `link_valid` and `link_id` fields are specifically used for Multi-Link Operation (MLO) in WiFi 7, where mac80211 needs to know which link a frame was received on. ## Why This Should Be Backported **1. Bug Fix Nature:** - This is clearly a bug fix that addresses undefined behavior caused by uninitialized fields - The commit message explicitly states this fixes "undefined behaviour in mac80211" - Similar to reference commit #2 (which was backported) that fixed uninitialized variables **2. User Impact:** - Uninitialized fields can cause mac80211 to make incorrect decisions about packet processing - May lead to packet drops, incorrect link handling, or other unpredictable wireless behavior - Monitor mode is commonly used by network analysis tools, making this user-facing **3. Risk Assessment:** - **Very Low Risk**: The change is minimal (single line initialization) - **No Side Effects**: Setting `link_valid = 0` is the correct default for monitor mode - **Safe Change**: Only affects the monitor Rx path, doesn't change core functionality **4. Code Pattern Consistency:** Looking at the regular Rx path in `dp_rx.c`, I can see the same pattern: ```c if (pubsta && pubsta->valid_links) { status->link_valid = 1; status->link_id = peer->link_id; } ``` The monitor path was missing the corresponding initialization, creating an inconsistency where: - Regular Rx path: Properly sets `link_valid = 1` when appropriate - Monitor Rx path: Left `link_valid` uninitialized (now fixed to `link_valid = 0`) **5. Containment:** - Change is confined to a single function in the monitor path - No architectural changes or new feature additions - Follows established kernel practices for field initialization **6. Stable Tree Criteria Match:** - ✅ Important bug fix (undefined behavior) - ✅ Minimal risk of regression - ✅ Small, contained change - ✅ No new features - ✅ Affects user-facing functionality (monitor mode) **7. Reference Precedent:** This follows the same pattern as the backported commit #2 which fixed uninitialized variables and commit #3 which fixed incorrect field usage, both of which were deemed suitable for backporting. The commit properly addresses a real bug that could affect users of monitor mode with ath12k WiFi 7 devices, with virtually no risk of introducing regressions.
drivers/net/wireless/ath/ath12k/dp_mon.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/net/wireless/ath/ath12k/dp_mon.c b/drivers/net/wireless/ath/ath12k/dp_mon.c index d22800e894850..b1350e60e2131 100644 --- a/drivers/net/wireless/ath/ath12k/dp_mon.c +++ b/drivers/net/wireless/ath/ath12k/dp_mon.c @@ -1970,6 +1970,8 @@ static void ath12k_dp_mon_rx_deliver_msdu(struct ath12k *ar, struct napi_struct bool is_mcbc = rxcb->is_mcbc; bool is_eapol_tkip = rxcb->is_eapol;
+ status->link_valid = 0; + if ((status->encoding == RX_ENC_HE) && !(status->flag & RX_FLAG_RADIOTAP_HE) && !(status->flag & RX_FLAG_SKIP_MONITOR)) { he = skb_push(msdu, sizeof(known));