Messages in this thread | | | Date | Thu, 4 Apr 2002 00:27:22 +0200 | From | Pavel Machek <> | Subject | Re: Warn users about machines with non-working WP bit |
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Hi!
> > This might be good idea, as those machines are not safe for multiuser > > systems. > > > > --- clean.2.5/arch/i386/mm/init.c Sun Mar 10 20:06:31 2002 > > +++ linux/arch/i386/mm/init.c Mon Mar 11 21:49:14 2002 > > @@ -383,7 +383,7 @@ > > local_flush_tlb(); > > > > if (!boot_cpu_data.wp_works_ok) { > > - printk("No.\n"); > > + printk("No (that's security hole).\n"); > > #ifdef CONFIG_X86_WP_WORKS_OK > > panic("This kernel doesn't support CPU's with broken WP. Recompile it for a 386!"); > > #endif > > > > Pavel > > The "bug" is really the lack of a feature present on 486+ cpus. A 386 > will allow the kernel to write to a write-protected user page (but not a > write-protected kernel page). In user mode, write protect works as it > should. The kernel works around this by doing extra checks when writing > to user pages (check the *_user() functions). It is not a security
It is, because those checks are racy when clone() is in use. Linus stated that few times. Pavel -- Casualities in World Trade Center: ~3k dead inside the building, cryptography in U.S.A. and free speech in Czech Republic. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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