lkml.org 
[lkml]   [2002]   [Apr]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Warn users about machines with non-working WP bit
    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/

    \
     
     \ /
      Last update: 2005-03-22 13:22    [W:3.201 / U:1.160 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site