wifi: mac80211: don't return unset power in ieee80211_get_tx_power()

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@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://lore.kernel.org/r/20230203023636.4418-1-pkshih@realtek.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index b25f612b39ebbbfc49682ccdaa3682d8af42a746..e751d4eba8f561324b40f655023e46bee754e4b5 100644 (file)
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -3079,6 +3079,10 @@ 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;
 }