[PATCH] iwlegacy: 4965-rs: avoid null pointer dereference error

[PATCH] iwlegacy: 4965-rs: avoid null pointer dereference error

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

il4965_rs_initialize_lq checks to see if sta is null, however, before that
check il4965_rs_use_green dereferences sta when intializing use_green.
Avoid a potential null pointer dereference error by only calling
il4965_rs_use_green after we are sure sta is not null.

Smatch analysis:

drivers/net/wireless/iwlegacy/4965-rs.c:2160 il4965_rs_initialize_lq() warn:
  variable dereferenced before check 'sta' (see line 2155)

Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/net/wireless/iwlegacy/4965-rs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/iwlegacy/4965-rs.c b/drivers/net/wireless/iwlegacy/4965-rs.c
index e8324b5..6c7493c 100644
--- a/drivers/net/wireless/iwlegacy/4965-rs.c
+++ b/drivers/net/wireless/iwlegacy/4965-rs.c
@@ -2152,7 +2152,7 @@ il4965_rs_initialize_lq(struct il_priv *il, struct ieee80211_conf *conf,
 	int rate_idx;
 	int i;
 	u32 rate;
-	u8 use_green = il4965_rs_use_green(il, sta);
+	u8 use_green;
 	u8 active_tbl = 0;
 	u8 valid_tx_ant;
 	struct il_station_priv *sta_priv;
@@ -2160,6 +2160,7 @@ il4965_rs_initialize_lq(struct il_priv *il, struct ieee80211_conf *conf,
 	if (!sta || !lq_sta)
 		return;
 
+	use_green = il4965_rs_use_green(il, sta);
 	sta_priv = (void *)sta->drv_priv;
 
 	i = lq_sta->last_txrate_idx;
-- 
1.8.1.2

Re: [PATCH] iwlegacy: 4965-rs: avoid null pointer dereference error

[Stanislaw Gruszka]

On Tue, Mar 26, 2013 at 05:35:23PM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> il4965_rs_initialize_lq checks to see if sta is null, however, before that
> check il4965_rs_use_green dereferences sta when intializing use_green.
> Avoid a potential null pointer dereference error by only calling
> il4965_rs_use_green after we are sure sta is not null.
> 
> Smatch analysis:
> 
> drivers/net/wireless/iwlegacy/4965-rs.c:2160 il4965_rs_initialize_lq() warn:
>   variable dereferenced before check 'sta' (see line 2155)
> 
> Signed-off-by: Colin Ian King <colin.king@canonical.com>

ACK