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From:   Jia-Ju Bai <baijiaju1990@gmail.com>
To:     gregkh@linuxfoundation.org, suniel.spartan@gmail.com
Cc:     devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org,
        Jia-Ju Bai <baijiaju1990@gmail.com>
Subject: [PATCH 2/6] staging: rtl8192u: Replace GFP_ATOMIC with GFP_KERNEL in ieee80211_tkip_init
Date:   Tue, 10 Apr 2018 20:23:29 +0800
Message-Id: <1523363009-30846-1-git-send-email-baijiaju1990@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

ieee80211_tkip_init() is never called in atomic context.

ieee80211_tkip_init() is only set as ".init" in
struct ieee80211_crypto_ops.
The call chains ending up at "->init" function are:
[1] ->init() <- ieee80211_wpa_set_encryption() <-
    ieee80211_wpa_supplicant_ioctl()
[2] ->init() <- ieee80211_wx_set_encode_ext_rsl() <-
    r8192_wx_set_enc_ext()
[3] ->init() <- ieee80211_wx_set_encode_rsl() <-
    r8192_wx_set_enc()

ieee80211_wpa_supplicant_ioctl(), r8192_wx_set_enc_ext() and
r8192_wx_set_enc() call mutex_lock(), which indicates these functions
are not called in atomic context.

Despite never getting called from atomic context,
ieee80211_tkip_init() calls kzalloc() with GFP_ATOMIC,
which does not sleep for allocation.
GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
which can sleep and improve the possibility of sucessful allocation.

This is found by a static analysis tool named DCNS written by myself.
And I also manually check it.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c b/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c
index 60ecfec..a7efaae 100644
--- a/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c
+++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c
@@ -66,7 +66,7 @@ static void *ieee80211_tkip_init(int key_idx)
 {
 	struct ieee80211_tkip_data *priv;
 
-	priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
+	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		goto fail;
 	priv->key_idx = key_idx;
-- 
1.9.1