[PATCH AUTOSEL 4.19 1/7] wifi: mac80211: don't return unset power in ieee80211_get_tx_power()

[Sasha Levin]

From: Ping-Ke Shih <pkshih@xxxxxxxxxxx>

[ Upstream commit e160ab85166e77347d0cbe5149045cb25e83937f ]

We can get a UBSAN warning if ieee80211_get_tx_power() returns the
INT_MIN value mac80211 internally uses for "unset power level".

 UBSAN: signed-integer-overflow in net/wireless/nl80211.c:3816:5
 -2147483648 * 100 cannot be represented in type 'int'
 CPU: 0 PID: 20433 Comm: insmod Tainted: G        WC OE
 Call Trace:
  dump_stack+0x74/0x92
  ubsan_epilogue+0x9/0x50
  handle_overflow+0x8d/0xd0
  __ubsan_handle_mul_overflow+0xe/0x10
  nl80211_send_iface+0x688/0x6b0 [cfg80211]
  [...]
  cfg80211_register_wdev+0x78/0xb0 [cfg80211]
  cfg80211_netdev_notifier_call+0x200/0x620 [cfg80211]
  [...]
  ieee80211_if_add+0x60e/0x8f0 [mac80211]
  ieee80211_register_hw+0xda5/0x1170 [mac80211]

In this case, simply return an error instead, to indicate
that no data is available.

Cc: Zong-Zhe Yang <kevin_yang@xxxxxxxxxxx>
Signed-off-by: Ping-Ke Shih <pkshih@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230203023636.4418-1-pkshih@xxxxxxxxxxx
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/mac80211/cfg.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 5659af1bec179..77d8ed184c1c4 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -2452,6 +2452,10 @@ static int ieee80211_get_tx_power(struct wiphy *wiphy,
 	else
 		*dbm = sdata->vif.bss_conf.txpower;
 
+	/* INT_MIN indicates no power level was set yet */
+	if (*dbm == INT_MIN)
+		return -EINVAL;
+
 	return 0;
 }
 
-- 
2.42.0