[PATCH AUTOSEL 6.18-6.12] wifi: iwlwifi: mvm: validate mac_link_id in session protect notif
From: Sasha Levin
Date: Mon Aug 31 2026 - 11:44:19 EST
From: Emmanuel Grumbach <emmanuel.grumbach@xxxxxxxxx>
[ Upstream commit 71245daf7d58a3c407c7e1422facce13ff6a584b ]
Check the mac_id before accessing the vif_id_to_mac array.
Assisted-by: GitHubCopilot:gpt-5.3-codex
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@xxxxxxxxx>
Link: https://patch.msgid.link/20260714141909.547ea470e686.I931445ae6f37bf0e1ef6f112c811712fc48af9c9@changeid
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
LLM Generated explanations, may be completely bogus:
# Stable Backport Analysis: `wifi: iwlwifi: mvm: validate mac_link_id in
session protect notif`
**Local tree:** Linux **6.18.44** (`v6.18.44-1-g2736c32da98b9`,
`VERSION=6 PATCHLEVEL=18 SUBLEVEL=44`)
---
## PHASE 1: COMMIT MESSAGE FORENSICS
### Step 1.1: Subject line
**Record:** `[wifi: iwlwifi: mvm]` `[validate]` — Add bounds validation
for `mac_link_id` in the session protection firmware notification
handler before indexing `vif_id_to_mac`.
### Step 1.2: Tags
**Record:**
- **Assisted-by:** GitHubCopilot:gpt-5.3-codex
- **Signed-off-by:** Emmanuel Grumbach \<emmanuel.grumbach@xxxxxxxxx\>
(iwlwifi maintainer)
- **Link:** https://patch.msgid.link/20260714141909.547ea470e686.I931445
ae6f37bf0e1ef6f112c811712fc48af9c9@changeid
- **Signed-off-by:** Miri Korenblit
\<miriam.rachel.korenblit@xxxxxxxxx\>
- **No** Fixes:, Reported-by:, Tested-by:, Reviewed-by:, Acked-by:, or
Cc: stable tags
- **Notable:** Maintainer-authored; no fuzzer or user bug report cited
### Step 1.3: Body
**Record:**
- **Bug:** `mac_link_id` from firmware is used to index `vif_id_to_mac`
without validating it first.
- **Symptom:** Not explicitly stated (no crash trace); implied mis-
handling of invalid firmware notification.
- **Root cause (from code):** `mac_link_id` is read as a 32-bit value
into an `int`, then passed to `iwl_mvm_rcu_dereference_vif_id()` which
takes `u8`. Values ≥ 256 truncate modulo 256 and can map to valid
indices 0–3, bypassing the helper’s `WARN_ON` bounds check.
### Step 1.4: Hidden bug fix?
**Record:** Yes. Despite the terse message, this is a real logic/safety
bug fix, not cosmetic cleanup. It mirrors an existing pattern in
`rxmq.c` for the same array.
---
## PHASE 2: DIFF ANALYSIS
### Step 2.1: Inventory
**Record:**
- **File:** `drivers/net/wireless/intel/iwlwifi/mvm/time-event.c` (+5
lines)
- **Function:** `iwl_mvm_rx_session_protect_notif()`
- **Scope:** Single-file, surgical fix
### Step 2.2: Code flow change
**Record:**
- **Before:** `id = le32_to_cpu(notif->mac_link_id)` → immediate
`iwl_mvm_rcu_dereference_vif_id(mvm, id, true)` (implicit `int` → `u8`
truncation).
- **After:** `IWL_FW_CHECK` on full `int id` against
`ARRAY_SIZE(mvm->vif_id_to_mac)` (4); early return if invalid; then
existing lookup proceeds.
- **Path:** Firmware RX notification handler
(`SESSION_PROTECTION_NOTIF`), normal runtime path during
association/session protection.
### Step 2.3: Bug mechanism
**Record:** **Logic / bounds-check bypass via type truncation.**
`NUM_MAC_INDEX_DRIVER` = 4, so valid indices are 0–3:
```15:16:drivers/net/wireless/intel/iwlwifi/fw/api/mac.h
#define NUM_MAC_INDEX_DRIVER MAC_INDEX_AUX
#define NUM_MAC_INDEX (NUM_MAC_INDEX_DRIVER + 1)
```
`iwl_mvm_rcu_dereference_vif_id()` only checks the truncated `u8`:
```1384:1391:drivers/net/wireless/intel/iwlwifi/mvm/mvm.h
static inline struct ieee80211_vif *
iwl_mvm_rcu_dereference_vif_id(struct iwl_mvm *mvm, u8 vif_id, bool rcu)
{
if (WARN_ON(vif_id >= ARRAY_SIZE(mvm->vif_id_to_mac)))
return NULL;
```
Example: `mac_link_id = 256` → `u8` = 0 → passes check → wrong VIF at
index 0. Values 4–255 are caught; values ≥ 256 congruent to 0–3 mod 256
are not.
Downstream effects in `iwl_mvm_rx_session_protect_notif()` include
modifying the wrong interface’s `time_event_data`, calling
`iwl_mvm_te_check_disconnect()` on the wrong VIF, and corrupting P2P ROC
state.
### Step 2.4: Fix quality
**Record:** Obviously correct; matches existing driver pattern in
`rxmq.c`:
```2618:2623:drivers/net/wireless/intel/iwlwifi/mvm/rxmq.c
/* >= means AUX MAC/link ID, no energy correction needed then */
if (IWL_FW_CHECK(mvm, id >= ARRAY_SIZE(mvm->vif_id_to_mac),
"invalid link ID %d\n", id))
return;
vif = iwl_mvm_rcu_dereference_vif_id(mvm, id, false);
```
**Regression risk:** Very low — early return only on invalid firmware
input; no API or locking changes.
---
## PHASE 3: GIT HISTORY INVESTIGATION
### Step 3.1: Blame
**Record:** `iwl_mvm_rx_session_protect_notif()` exists at lines
953–1025 in this tree. Blame attributes lines to merge commit
`5d324e5159d9e` (shallow history for this file). Function and handler
registration in `ops.c` are present in 6.18.44.
### Step 3.2: Fixes: tag
**Record:** N/A — no Fixes: tag in commit message.
### Step 3.3: Related file history
**Record:** `git log --oneline -20 -- time-event.c` returns only the usb
merge commit (limited per-file history in this checkout). The beacon-
filter validation in `rxmq.c` at line 2619 establishes precedent for
this exact check pattern.
### Step 3.4: Author context
**Record:** Emmanuel Grumbach is iwlwifi maintainer. Miri Korenblit is
an active iwlwifi contributor. High credibility for driver correctness.
### Step 3.5: Dependencies
**Record:** Standalone; no series or prerequisite commits. Uses existing
`IWL_FW_CHECK` macro from `fw/dbg.h`. No new structures or APIs.
---
## PHASE 4: MAILING LIST AND EXTERNAL RESEARCH
### Step 4.1: Original discussion
**Record:** `b4 dig` on HEAD did not match this patch. Link URL and
lore.kernel.org blocked by Anubis bot protection — could not read
thread. **UNVERIFIED:** reviewer feedback and stable nominations.
### Step 4.2: Reviewers
**Record:** **UNVERIFIED** — `b4 dig -w` not run (no commit hash
available in this evaluation context).
### Step 4.3: Bug report
**Record:** No Reported-by or syzbot link. Bug inferred from code
analysis and driver consistency with `rxmq.c`.
### Step 4.4: Related patches
**Record:** Same validation pattern exists for beacon filter
notifications in `rxmq.c`. This commit closes a gap in `time-event.c`
where `IWL_FW_CHECK` is currently absent.
### Step 4.5: Stable list
**Record:** **UNVERIFIED** — lore stable search blocked.
---
## PHASE 5: CODE SEMANTIC ANALYSIS
### Step 5.1: Key functions
**Record:** `iwl_mvm_rx_session_protect_notif()` (modified); uses
`iwl_mvm_rcu_dereference_vif_id()`, `iwl_mvm_te_check_disconnect()`,
`iwl_mvm_te_clear_data()`, `ieee80211_ready_on_channel()` /
`ieee80211_remain_on_channel_expired()`.
### Step 5.2: Callers
**Record:** Registered in `ops.c` as RX handler for
`SESSION_PROTECTION_NOTIF` under `MAC_CONF_GROUP` — invoked on every
session-protection firmware notification for Intel MVM devices.
### Step 5.3: Callees
**Record:** RCU lookup, spinlocks on `time_event_lock`, mac80211
callbacks. Invalid ID can corrupt another interface’s session-protection
/ ROC state.
### Step 5.4: Reachability
**Record:** Triggered by iwlwifi firmware notifications during WiFi
association, session protection, and P2P ROC. Reachable during normal
WiFi use on Intel hardware (`CONFIG_IWLMVM`).
### Step 5.5: Similar patterns
**Record:** `rxmq.c` lines 272–273 and 2619–2621 already validate before
`vif_id_to_mac` access. `time-event.c` is the outlier lacking this
check.
---
## PHASE 6: CROSS-REFERENCE AGAINST LOCAL TREE
### Step 6.1: Buggy code present?
**Record:** **Yes.** Current `time-event.c` at lines 958–965 has no
`IWL_FW_CHECK`; passes raw `int id` directly to
`iwl_mvm_rcu_dereference_vif_id()`. Fix is **not** yet applied in
6.18.44.
### Step 6.2: Backport complications
**Record:** Clean apply expected — 5-line insertion before
`rcu_read_lock()`. No conflicting changes observed. `IWL_FW_CHECK` and
`vif_id_to_mac` already exist in this tree.
### Step 6.3: Related fixes already present?
**Record:** Beacon-filter path in `rxmq.c` already has this validation.
No duplicate fix for session-protect in this tree (`grep` found no
"Invalid mac_link_id" string).
---
## PHASE 7: SUBSYSTEM CONTEXT
### Step 7.1: Subsystem criticality
**Record:** `drivers/net/wireless/intel/iwlwifi/mvm` — **IMPORTANT**
(Intel WiFi, widely deployed on laptops/desktops).
### Step 7.2: Activity
**Record:** iwlwifi actively maintained; MLD path added alongside legacy
MVM. This fix targets the MVM notification path still used by many
devices in 6.18.y.
---
## PHASE 8: IMPACT AND RISK
### Step 8.1: Who is affected
**Record:** Users of Intel WiFi with MVM driver (`CONFIG_IWLMVM=y/m`),
during session protection / association / P2P ROC.
### Step 8.2: Trigger conditions
**Record:** Firmware sends `SESSION_PROTECTION_NOTIF` with `mac_link_id`
≥ 4, or ≥ 256 with value mod 256 in 0–3. Requires firmware misbehavior
or edge-case firmware state — not everyday, but plausible and not user-
privilege-dependent.
### Step 8.3: Failure mode severity
**Record:** Wrong-interface session-protection state corruption;
possible spurious disconnect (`iwl_mvm_te_check_disconnect`) or ROC
misbehavior on an unrelated VIF. **Severity: MEDIUM–HIGH** (functional
WiFi breakage, not kernel oops, but user-visible connectivity impact).
### Step 8.4: Risk–benefit
**Record:**
- **Benefit:** Prevents cross-interface state corruption from invalid
firmware notifications; aligns with existing driver defensive pattern.
- **Risk:** Very low — 5 lines, early return on invalid input only.
- **Ratio:** Favorable for stable.
---
## PHASE 9: FINAL SYNTHESIS
### Step 9.1: Evidence summary
**FOR backport:**
- Real bug: `int`→`u8` truncation bypasses bounds checking for
`vif_id_to_mac`
- Wrong VIF can be operated on (disconnect, time-event corruption)
- Small, surgical, maintainer-authored fix
- Matches established pattern in same driver (`rxmq.c`)
- Buggy code confirmed present in Linux 6.18.44; fix not yet applied
- No new APIs or features
**AGAINST backport:**
- No explicit crash report, syzbot, or user Reported-by
- Commit message is minimal
- Trigger requires invalid firmware `mac_link_id` (not proven in the
wild from available sources)
**UNRESOLVED:**
- Mailing list review discussion (lore blocked)
- Whether a specific production firmware bug motivated this fix
### Step 9.2: Stable rules checklist
| Criterion | Result |
|-----------|--------|
| 1. Obviously correct and tested? | **PASS** — matches existing
`rxmq.c` pattern; maintainer SOB |
| 2. Fixes a real bug? | **PASS** — truncation bypass is verifiable in
code |
| 3. Important issue? | **PASS** — wrong-interface WiFi state corruption
/ disconnect |
| 4. Small and contained? | **PASS** — 5 lines, one function |
| 5. No new features/APIs? | **PASS** |
| 6. Can apply to local tree? | **PASS** — code exists; clean apply
expected |
### Step 9.3: Exception categories
**Record:** N/A (not device ID, quirk, DT, build, or docs — standard
driver bug fix).
### Step 9.4: Decision rationale
For **this** tree (6.18.44), the vulnerable code is present and the fix
is a minimal, obviously-correct defensive validation that prevents
wrong-interface state corruption when firmware sends an out-of-range
`mac_link_id`. It follows an established iwlwifi pattern and carries
negligible regression risk.
---
## Verification
- **[Phase 1]** Parsed subject, tags, body from user-provided commit
message
- **[Phase 2]** Read `time-event.c` lines 953–1025: fix absent,
vulnerable code confirmed
- **[Phase 2]** Read `mvm.h` lines 1384–1394: `u8` parameter + `WARN_ON`
only on truncated value
- **[Phase 2]** Read `mac.h` line 15: `NUM_MAC_INDEX_DRIVER = 4`
- **[Phase 2]** Read `rxmq.c` lines 2618–2623: identical validation
pattern exists
- **[Phase 2]** Read `fw/dbg.h` lines 334–342: `IWL_FW_CHECK` logs and
returns condition
- **[Phase 3]** `git describe HEAD`: v6.18.44-1-g2736c32da98b9
- **[Phase 3]** `git blame -L 953,970 time-event.c`: function present in
tree
- **[Phase 3]** `grep IWL_FW_CHECK time-event.c`: no matches (fix not
present)
- **[Phase 4]** `b4 dig -c HEAD`: no match for this patch
- **[Phase 4]** WebFetch patch.msgid.link and lore.kernel.org: blocked
by Anubis — **UNVERIFIED**
- **[Phase 5]** `grep iwl_mvm_rx_session_protect_notif`: handler in
`ops.c` line 355
- **[Phase 5]** `grep iwl_mvm_rcu_dereference_vif_id mvm/`: multiple
call sites; `time-event.c` lacks pre-check
- **[Phase 6]** Confirmed buggy code at lines 958–965 without
`IWL_FW_CHECK`
- **[Phase 6]** `grep "Invalid mac_link_id"`: no results (fix not
applied)
- **[Phase 8]** Traced downstream effects:
`iwl_mvm_te_check_disconnect`, ROC callbacks on wrong VIF
---
**YES**Two background git history lookups (`git log -S` for when
`iwl_mvm_rx_session_protect_notif` was introduced, and a repo-depth
check) timed out and were killed — likely due to the large tree and the
accidental `--all` on one of them.
That didn’t change the backport verdict: the vulnerable code is present
in this 6.18.44 tree, the fix is a 5-line bounds check matching an
existing `rxmq.c` pattern, and the analysis already concluded **YES**.
drivers/net/wireless/intel/iwlwifi/mvm/time-event.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/time-event.c b/drivers/net/wireless/intel/iwlwifi/mvm/time-event.c
index 1a3a8a3f0fb49..356f68f5e6ac3 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/time-event.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/time-event.c
@@ -960,6 +960,11 @@ void iwl_mvm_rx_session_protect_notif(struct iwl_mvm *mvm,
struct ieee80211_vif *vif;
struct iwl_mvm_vif *mvmvif;
+ if (IWL_FW_CHECK(mvm, id >= ARRAY_SIZE(mvm->vif_id_to_mac),
+ "Invalid mac_link_id (%d) in session protect notif\n",
+ id))
+ return;
+
rcu_read_lock();
/* note we use link ID == MAC ID */
--
2.53.0