linux-kernel - [PATCH v2] wifi: nl80211: reject cooked mode if it is set along with other flags

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Message-ID: <20250131152657.5606-1-v.shevtsov@mt-integration.ru>
Date: Fri, 31 Jan 2025 20:26:55 +0500
From: Vitaliy Shevtsov <v.shevtsov@...integration.ru>
To: Johannes Berg <johannes@...solutions.net>
CC: Vitaliy Shevtsov <v.shevtsov@...integration.ru>, Michael Wu
	<flamingice@...rmilk.net>, "John W. Linville" <linville@...driver.com>,
	<linux-wireless@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<lvc-project@...uxtesting.org>,
	<syzbot+2e5c1e55b9e5c28a3da7@...kaller.appspotmail.com>
Subject: [PATCH v2] wifi: nl80211: reject cooked mode if it is set along with other flags

It is possible to set both MONITOR_FLAG_COOK_FRAMES and MONITOR_FLAG_ACTIVE
flags simultaneously on the same monitor interface from the userspace. This
causes a sub-interface to be created with no IEEE80211_SDATA_IN_DRIVER bit
set because the monitor interface is in the cooked state and it takes
precedence over all other states. When the interface is then being deleted
the kernel calls WARN_ONCE() from check_sdata_in_driver() because of missing
that bit.

Fix this by rejecting MONITOR_FLAG_COOK_FRAMES if it is set along with
other flags.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 66f7ac50ed7c ("nl80211: Add monitor interface configuration flags")
Reported-by: syzbot+2e5c1e55b9e5c28a3da7@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2e5c1e55b9e5c28a3da7
Signed-off-by: Vitaliy Shevtsov <v.shevtsov@...integration.ru>
---
v2: update patch name and description,
    reject cooked mode if the one is set along with other flags.

 net/wireless/nl80211.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index d7d3da0f6833..fdb2aac951d1 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -4220,6 +4220,11 @@ static int parse_monitor_flags(struct nlattr *nla, u32 *mntrflags)
 		if (flags[flag])
 			*mntrflags |= (1<<flag);
 
+	/* cooked monitor mode is incompatible with other modes */
+	if (*mntrflags & MONITOR_FLAG_COOK_FRAMES &&
+	    *mntrflags != MONITOR_FLAG_COOK_FRAMES)
+		return -EOPNOTSUPP;
+
 	*mntrflags |= MONITOR_FLAG_CHANGED;
 
 	return 0;
-- 
2.48.1