[PATCH] Revert "staging:r8188eu: use lib80211 CCMP decrypt"

[Larry Finger]

On 12/30/18 12:39 PM, Michael Straube wrote:
> Commit 6bd082af7e36 ("staging:r8188eu: use lib80211 CCMP decrypt")
> is causing hardfreeze whenever the driver tries to connect to my wifi
> network. That makes the driver unusable on my system. Reverting the
> commit fixes the issue and the driver works properly.
> 
> Dec 29 19:21:17 gentoo kernel: BUG: scheduling while atomic: swapper/6/0/0x00000100

Michael,

I have verified the freezes that you see. Although I have not been able to 
capture the console dump, I think we are likely seeing the same problem.

I do have a work-around in that I have not gotten any freezes when I force 
module lib80211_crypt_ccmp to be loaded before I load module r8188eu. This clue 
was used in finding what seems to be a good fix.

I do not know anything about demand loading of modules using 
try_then_request_module(); however, I noticed that the macro actually calls 
__request_module(), which has the following comment:

  * Load a module using the user mode module loader. The function returns
  * zero on success or a negative errno code or positive exit code from
  * "modprobe" on failure. Note that a successful module load does not mean
  * the module did not then unload and exit on an error of its own. Callers
  * must check that the service they requested is now available not blindly
  * invoke it.

I note that it says "user mode module loader". Routine rtw_aes_decrypt() is 
likely inside some sort of locking, which leads to the "scheduling while atomic" 
bug that you see. As a result, I suspect that the module is not loaded, and that 
leads to the NULL dereference when the module is accessed. Please try the 
one-line patch attached, which forces lib80211 to load when r8188eu is loaded. 
With this patch, I have been connected to an AES-encrypted AP for nearly 3 hours 
with no problems.

Larry


-------------- next part --------------
diff --git a/drivers/staging/rtl8188eu/core/rtw_security.c b/drivers/staging/rtl8188eu/core/rtw_security.c
index f7407632e80b..052656a22821 100644
--- a/drivers/staging/rtl8188eu/core/rtw_security.c
+++ b/drivers/staging/rtl8188eu/core/rtw_security.c
@@ -1291,7 +1291,7 @@ u32 rtw_aes_decrypt(struct adapter *padapter, u8 *precvframe)
 			struct sk_buff *skb = ((struct recv_frame *)precvframe)->pkt;
 			void *crypto_private = NULL;
 			u8 *key, *pframe = skb->data;
-			struct lib80211_crypto_ops *crypto_ops = try_then_request_module(lib80211_get_crypto_ops("CCMP"), "lib80211_crypt_ccmp");
+			struct lib80211_crypto_ops *crypto_ops = lib80211_get_crypto_ops("CCMP");
 			struct security_priv *psecuritypriv = &padapter->securitypriv;
 			char iv[8], icv[8];