Re: b43 crashes on rmmod (bcm4331)

["Michael Büsch" <m@bues.ch>]

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On Wed, 13 Jun 2018 13:09:05 +0200
Michael Büsch <m@bues.ch> wrote:

> On Wed, 13 Jun 2018 14:01:53 +0300
> Wirz <spam@lukas-wirz.de> wrote:
> 
> > > CONFIG_B43_HWRNG completely switches off hwrng support in b43.
> > > I don't see how a change in hwrng core could still lead to a crash in
> > > b43 with this option switched off.
> > > 
> > > What do you mean by "manually in the .config"?    
> > 
> > What I meant is, that I have outcommented the line 'CONFIG_B43_HWRNG=y'
> > in .config.
> >   
> > > Can you try to properly switch off the setting with make menuconfig and
> > > then recompile everything from scratch (make clean)?    
> > 
> > I was intending to do that before, but I cannot find the option for
> > that.  Searching for b43_hwrng in menuconfig only shows the dependencies
> > of that option, and the Kconfig file where it is defined, but not the
> > path in menuconfig.  Do I indirectly set CONFIG_B43_HWRNG through the
> > parameters it depends on?  I'm sorry, but this is obviously above my
> > level of expertise ...  
> 
> Whoops, sorry. You are right. This is an automatic config option.
> That also means your manual editing of .config would be overridden.
> 
> You can edit drivers/net/wireless/broadcom/b43/Kconfig
> go to the section config B43_HWRNG
> and change 'default y' to 'default n'
> 
> That should disable it.



Could you please also try the attached patch?
There seems to be a problem in hwrng core in that it does not disable
the current RNG, if the new RNG fails to initialize.
I don't know if that's the problem here, though.


diff --git a/drivers/char/hw_random/core.c
b/drivers/char/hw_random/core.c index 91bb98c42a1c..aaf9e5afaad4 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -516,11 +516,18 @@ EXPORT_SYMBOL_GPL(hwrng_register);
 
 void hwrng_unregister(struct hwrng *rng)
 {
+	int err;
+
 	mutex_lock(&rng_mutex);
 
 	list_del(&rng->list);
-	if (current_rng == rng)
-		enable_best_rng();
+	if (current_rng == rng) {
+		err = enable_best_rng();
+		if (err) {
+			drop_current_rng();
+			cur_rng_set_by_user = 0;
+		}
+	}
 
 	if (list_empty(&rng_list)) {
 		mutex_unlock(&rng_mutex);



-- 
Michael

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diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 91bb98c42a1c..aaf9e5afaad4 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -516,11 +516,18 @@ EXPORT_SYMBOL_GPL(hwrng_register);
 
 void hwrng_unregister(struct hwrng *rng)
 {
+	int err;
+
 	mutex_lock(&rng_mutex);
 
 	list_del(&rng->list);
-	if (current_rng == rng)
-		enable_best_rng();
+	if (current_rng == rng) {
+		err = enable_best_rng();
+		if (err) {
+			drop_current_rng();
+			cur_rng_set_by_user = 0;
+		}
+	}
 
 	if (list_empty(&rng_list)) {
 		mutex_unlock(&rng_mutex);

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