On Mon, Sep 03, 2012 at 12:38:31AM +0800, Fengguang Wu wrote:
> On Sun, Sep 02, 2012 at 03:41:34PM +0200, Bjørn Mork wrote:
> > Fengguang Wu <fengguang.wu@xxxxxxxxx> writes:
> >
> > > After the __devinit* removal series, I can still get kernel panic in
> > > show_uevent(). So there are more sources of bug..
> > >
> > > Debug patch:
> > >
> > > @@ -343,8 +343,11 @@ static ssize_t show_uevent(struct device
> > > goto out;
> > >
> > > /* copy keys to file */
> > > - for (i = 0; i < env->envp_idx; i++)
> > > + dev_err(dev, "uevent %d env[%d]: %s/.../%s\n", env->buflen, env->envp_idx, top_kobj->name, dev->kobj.name);
> > > + for (i = 0; i < env->envp_idx; i++) {
> > > + printk(KERN_ERR "uevent %d env[%d]: %s\n", (int)count, i, env->envp[i]);
> > > count += sprintf(&buf[count], "%s\n", env->envp[i]);
> > > + }
> > >
> > > Oops message, the env[] is again not properly initilized:
> > >
> > > [ 44.068623] input input0: uevent 61 env[805306368]: input0/.../input0
> > > [ 44.069552] uevent 0 env[0]: (null)
> >
> > This is a completely different CONFIG_HOTPLUG problem, only
> > demonstrating another reason why CONFIG_HOTPLUG should go away. I had a
> > hard time trying to disable it anyway ;-)
> >
> > The problem this time is lots of code assuming that a call to
> > add_uevent_var() will guarantee that env->buflen > 0. This is not true
> > if CONFIG_HOTPLUG is unset. So things like this end up overwriting
> > env->envp_idx because the array index is -1:
> >
> > if (add_uevent_var(env, "MODALIAS="))
> > return -ENOMEM;
> > len = input_print_modalias(&env->buf[env->buflen - 1],
> > sizeof(env->buf) - env->buflen,
> > dev, 0);
> >
> >
> > Don't know what the best action is, given that there seem to be a *lot*
> > of this around the kernel. This patch "fixes" the problem for me, but I
>
> It also works reliably for me: 300 boots without a single failure.
>
> Tested-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Thanks for figuring this out. I'll apply it for 3.6, but work to get
rid of CONFIG_HOTPLUG completly for 3.7 as it just causes problems.
greg k-h
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