2021-11-15 06:09:31

by Bixuan Cui

Subject: [PATCH -next] mac80211: fix suspicious RCU usage in ieee80211_set_tx_power()

Fix suspicious RCU usage warning:

=============================
WARNING: suspicious RCU usage
5.15.0-syzkaller #0 Not tainted
-----------------------------
net/mac80211/cfg.c:2710 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
2 locks held by syz-executor.0/3744:
#0: ffffffff8d199ed0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40
net/netlink/genetlink.c:802
#1: ffff8880282f8628 (&rdev->wiphy.mtx){+.+.}-{3:3}, at: wiphy_lock
include/net/cfg80211.h:5377 [inline]
#1: ffff8880282f8628 (&rdev->wiphy.mtx){+.+.}-{3:3}, at:
nl80211_set_wiphy+0x1c6/0x2c20 net/wireless/nl80211.c:3287

stack backtrace:
CPU: 0 PID: 3744 Comm: syz-executor.0 Not tainted 5.15.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
ieee80211_set_tx_power+0x74c/0x860 net/mac80211/cfg.c:2710
rdev_set_tx_power net/wireless/rdev-ops.h:580 [inline]
nl80211_set_wiphy+0xd5b/0x2c20 net/wireless/nl80211.c:3384
genl_family_rcv_msg_doit+0x228/0x320 net/netlink/genetlink.c:731
genl_family_rcv_msg net/netlink/genetlink.c:775 [inline]
genl_rcv_msg+0x328/0x580 net/netlink/genetlink.c:792
netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2491
genl_rcv+0x24/0x40 net/netlink/genetlink.c:803
netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1345
netlink_sendmsg+0x86d/0xda0 net/netlink/af_netlink.c:1916
sock_sendmsg_nosec net/socket.c:704 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:724
____sys_sendmsg+0x6e8/0x810 net/socket.c:2409
___sys_sendmsg+0xf3/0x170 net/socket.c:2463
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2492
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported-by: [email protected]
Signed-off-by: Bixuan Cui <[email protected]>
---
net/mac80211/cfg.c | 27 +++++++++++++++++++--------
1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 1ab8483..14fbe9e 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -2702,14 +2702,19 @@ static int ieee80211_set_tx_power(struct wiphy *wiphy,
enum nl80211_tx_power_setting txp_type = type;
bool update_txp_type = false;
bool has_monitor = false;
+ int ret = 0;
+
+ rtnl_lock();

if (wdev) {
sdata = IEEE80211_WDEV_TO_SUB_IF(wdev);

if (sdata->vif.type == NL80211_IFTYPE_MONITOR) {
sdata = rtnl_dereference(local->monitor_sdata);
- if (!sdata)
- return -EOPNOTSUPP;
+ if (!sdata) {
+ ret = -EOPNOTSUPP;
+ goto out;
+ }
}

switch (type) {
@@ -2719,8 +2724,10 @@ static int ieee80211_set_tx_power(struct wiphy *wiphy,
break;
case NL80211_TX_POWER_LIMITED:
case NL80211_TX_POWER_FIXED:
- if (mbm < 0 || (mbm % 100))
- return -EOPNOTSUPP;
+ if (mbm < 0 || (mbm % 100)) {
+ ret = -EOPNOTSUPP;
+ goto out;
+ }
sdata->user_power_level = MBM_TO_DBM(mbm);
break;
}
@@ -2732,7 +2739,7 @@ static int ieee80211_set_tx_power(struct wiphy *wiphy,

ieee80211_recalc_txpower(sdata, update_txp_type);

- return 0;
+ goto out;
}

switch (type) {
@@ -2742,8 +2749,10 @@ static int ieee80211_set_tx_power(struct wiphy *wiphy,
break;
case NL80211_TX_POWER_LIMITED:
case NL80211_TX_POWER_FIXED:
- if (mbm < 0 || (mbm % 100))
- return -EOPNOTSUPP;
+ if (mbm < 0 || (mbm % 100)) {
+ ret = -EOPNOTSUPP;
+ goto out;
+ }
local->user_power_level = MBM_TO_DBM(mbm);
break;
}
@@ -2778,7 +2787,9 @@ static int ieee80211_set_tx_power(struct wiphy *wiphy,
}
}

- return 0;
+out:
+ rtnl_unlock();
+ return ret;
}

static int ieee80211_get_tx_power(struct wiphy *wiphy,
--
1.8.3.1

2021-11-26 12:39:36

by Johannes Berg

Subject: Re: [PATCH -next] mac80211: fix suspicious RCU usage in ieee80211_set_tx_power()

On Mon, 2021-11-15 at 14:09 +0800, Bixuan Cui wrote:
>
> diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
> index 1ab8483..14fbe9e 100644
> --- a/net/mac80211/cfg.c
> +++ b/net/mac80211/cfg.c
> @@ -2702,14 +2702,19 @@ static int ieee80211_set_tx_power(struct wiphy *wiphy,
> enum nl80211_tx_power_setting txp_type = type;
> bool update_txp_type = false;
> bool has_monitor = false;
> + int ret = 0;
> +
> + rtnl_lock();
>

This will almost certainly result in lockups, or at least lockdep
complaints, that's just wrong.

johannes