On Wed, 18 Nov 2015 15:20:05 -0800 Daniel Cashman <dcashman@xxxxxxxxxxx> wrote: > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -1568,6 +1568,28 @@ static struct ctl_table vm_table[] = { > .mode = 0644, > .proc_handler = proc_doulongvec_minmax, > }, > +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS > + { > + .procname = "mmap_rnd_bits", > + .data = &mmap_rnd_bits, > + .maxlen = sizeof(mmap_rnd_bits), > + .mode = 0644, Is there any harm in permitting the attacker to read these values? And is there any benefit in permitting non-attackers to read them? > + .proc_handler = proc_dointvec_minmax, > + .extra1 = &mmap_rnd_bits_min, > + .extra2 = &mmap_rnd_bits_max, > + }, > +#endif > +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS > + { > + .procname = "mmap_rnd_compat_bits", > + .data = &mmap_rnd_compat_bits, > + .maxlen = sizeof(mmap_rnd_compat_bits), > + .mode = 0644, > + .proc_handler = proc_dointvec_minmax, > + .extra1 = &mmap_rnd_compat_bits_min, > + .extra2 = &mmap_rnd_compat_bits_max, > + }, > +#endif > > ... > > +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS > +int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN; > +int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX; > +int mmap_rnd_bits = CONFIG_ARCH_MMAP_RND_BITS; > +#endif > +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS > +int mmap_rnd_compat_bits_min = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MIN; > +int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX; > +int mmap_rnd_compat_bits = CONFIG_ARCH_MMAP_RND_COMPAT_BITS; These could be __read_mostly. If one believes in such things. One effect of __read_mostly is to clump the write-often stuff into the same cachelines and I've never been convinced that one outweighs the other... -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>