[PATCH AUTOSEL 5.15 07/11] wifi: mac80211: drop invalid source address OCB frames

[Sasha Levin <sashal@kernel.org>]

From: Johannes Berg <johannes.berg@intel.com>

[ Upstream commit d1b1a5eb27c4948e8811cf4dbb05aaf3eb10700c ]

In OCB, don't accept frames from invalid source addresses
(and in particular don't try to create stations for them),
drop the frames instead.

Reported-by: syzbot+8b512026a7ec10dcbdd9@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/r/6788d2d9.050a0220.20d369.0028.GAE@google.com/
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Tested-by: syzbot+8b512026a7ec10dcbdd9@syzkaller.appspotmail.com
Link: https://patch.msgid.link/20250616171838.7433379cab5d.I47444d63c72a0bd58d2e2b67bb99e1fea37eec6f@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

**YES**

This commit should be backported to stable kernel trees. Here's my
extensive analysis:

## Security Vulnerability Fixed

The commit fixes a clear security vulnerability in OCB (Outside Context
of a BSS) mode where frames with invalid source addresses are accepted
and processed. Looking at the code change:

```c
+               /* reject invalid/our STA address */
+               if (!is_valid_ether_addr(hdr->addr2) ||
+                   ether_addr_equal(sdata->dev->dev_addr, hdr->addr2))
+                       return false;
```

This adds critical validation that was missing, preventing:

1. **Invalid MAC addresses** (all zeros, broadcast/multicast addresses)
   from being accepted
2. **Self-spoofing attacks** where frames appear to come from the
   device's own address

## Comparison with Similar Historical Fixes

This fix follows the exact pattern of Similar Commit #1 (Backport
Status: YES):
- That commit added `!is_valid_ether_addr(hdr->addr2)` check to ADHOC
  mode
- It fixed WARN_ON spam in `sta_info_insert_check()`
- It was deemed suitable for stable backporting

The OCB fix addresses the same class of vulnerability in a different
interface mode.

## Impact Without the Fix

Without this validation, the `ieee80211_ocb_rx_no_sta()` function would:
1. Create station entries for invalid addresses
2. Potentially trigger WARN_ON messages causing log spam
3. Allow resource exhaustion attacks by creating many invalid stations
4. Risk crashes or undefined behavior from invalid station entries

## Stable Backport Criteria Met

1. **Fixes a real bug**: Yes - invalid frames are incorrectly accepted
2. **Security impact**: Yes - potential DoS via resource exhaustion
3. **Small and contained**: Yes - adds 4 lines of validation
4. **Clear fix**: Yes - straightforward address validation
5. **No new features**: Correct - only adds missing validation
6. **Tested**: Yes - verified by syzbot

## Not Like the "NO" Examples

Unlike the commits marked for NO backporting:
- This is not adding new functionality (like link-addressed frames
  support)
- This is not a code cleanup or optimization
- This is fixing a concrete security issue reported by syzbot
- This has minimal risk of regression

The fix is essential for OCB mode security and should be backported to
all stable kernels that support OCB mode (since 2014).

 net/mac80211/rx.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 26943c93f14c4..6c160ff2aab90 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -4168,6 +4168,10 @@ static bool ieee80211_accept_frame(struct ieee80211_rx_data *rx)
 		if (!multicast &&
 		    !ether_addr_equal(sdata->dev->dev_addr, hdr->addr1))
 			return false;
+		/* reject invalid/our STA address */
+		if (!is_valid_ether_addr(hdr->addr2) ||
+		    ether_addr_equal(sdata->dev->dev_addr, hdr->addr2))
+			return false;
 		if (!rx->sta) {
 			int rate_idx;
 			if (status->encoding != RX_ENC_LEGACY)
-- 
2.39.5