On Wed, Oct 18, 2017 at 02:44:31PM +0900, Sergey Senozhatsky wrote:
> On (10/18/17 15:21), Tobin C. Harding wrote:
> [..]
> > diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> > index 86c3385b9eb3..4609738cd2cd 100644
> > --- a/lib/vsprintf.c
> > +++ b/lib/vsprintf.c
> > @@ -33,6 +33,8 @@
> > #include <linux/uuid.h>
> > #include <linux/of.h>
> > #include <net/addrconf.h>
> > +#include <linux/siphash.h>
> > +#include <linux/spinlock.h>
> > #ifdef CONFIG_BLOCK
> > #include <linux/blkdev.h>
> > #endif
> > @@ -1591,6 +1593,70 @@ char *device_node_string(char *buf, char *end,
> > struct device_node *dn,
> > return widen_string(buf, buf - buf_start, end, spec);
> > }
> >
> > +/* protects ptr_secret and have_key */
> > +DEFINE_SPINLOCK(key_lock);
> > +static siphash_key_t ptr_secret __read_mostly;
> > +static atomic_t have_key = ATOMIC_INIT(0);
> > +
> > +static int initialize_ptr_secret(void)
> > +{
> > + spin_lock(&key_lock);
> > + if (atomic_read(&have_key) == 1)
> > + goto unlock;
> > +
> > + get_random_bytes(&ptr_secret, sizeof(ptr_secret));
> > + atomic_set(&have_key, 1);
> > +
> > +unlock:
> > + spin_unlock(&key_lock);
> > + return 0;
> > +}
>
> is this spinlock legal? what happens if we are getting interrupted by NMI?
I think we can do without the spinlock. I think I was already told that when
I tried to put it [some where else] in v1.
It's fun failing in public ;)
> printk()
> vprintk_emit()
> vscnprintf()
> pointer()
> ptr_to_id()
> initialize_ptr_secret()
> spin_lock(&key_lock)
>
> ----> NMI
>
> printk()
> printk_safe_log_store()
> vscnprintf()
> pointer()
> ptr_to_id()
> initialize_ptr_secret()
> spin_lock(&key_lock) <<<<
>
>
> or am I completely misreading the patch? sorry if so.
>
> -ss
thanks,
Tobin.
