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SubjectRe: x86: Make sure IDT is page aligned
On Thu, Jul 18, 2013 at 06:36:07PM -0700, Kees Cook wrote:
> On Thu, Jul 18, 2013 at 6:30 PM, Greg KH <gregkh@linuxfoundation.org> wrote:
> > On Fri, Jul 19, 2013 at 01:15:26AM +0000, Linux Kernel Mailing List wrote:
> >> Gitweb: http://git.kernel.org/linus/;a=commit;h=4df05f361937ee86e5a8c9ead8aeb6a19ea9b7d7
> >> Commit: 4df05f361937ee86e5a8c9ead8aeb6a19ea9b7d7
> >> Parent: 5ff560fd48d5b3d82fa0c3aff625c9da1a301911
> >> Author: Kees Cook <keescook@chromium.org>
> >> AuthorDate: Tue Jul 16 11:34:41 2013 -0700
> >> Committer: H. Peter Anvin <hpa@linux.intel.com>
> >> CommitDate: Tue Jul 16 15:14:48 2013 -0700
> >>
> >> x86: Make sure IDT is page aligned
> >>
> >> Since the IDT is referenced from a fixmap, make sure it is page aligned.
> >> Merge with 32-bit one, since it was already aligned to deal with F00F
> >> bug. Since bss is cleared before IDT setup, it can live there. This also
> >> moves the other *_idt_table variables into common locations.
> >>
> >> This avoids the risk of the IDT ever being moved in the bss and having
> >> the mapping be offset, resulting in calling incorrect handlers. In the
> >> current upstream kernel this is not a manifested bug, but heavily patched
> >> kernels (such as those using the PaX patch series) did encounter this bug.
> >>
> >> The tables other than idt_table technically do not need to be page
> >> aligned, at least not at the current time, but using a common
> >> declaration avoids mistakes. On 64 bits the table is exactly one page
> >> long, anyway.
> >>
> >> Signed-off-by: Kees Cook <keescook@chromium.org>
> >> Link: http://lkml.kernel.org/r/20130716183441.GA14232@www.outflux.net
> >> Reported-by: PaX Team <pageexec@gmail.com>
> >> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
> >> ---
> >> arch/x86/kernel/head_64.S | 15 ---------------
> >> arch/x86/kernel/tracepoint.c | 6 ++----
> >> arch/x86/kernel/traps.c | 12 ++++++------
> >> 3 files changed, 8 insertions(+), 25 deletions(-)
> >
> > This patch is now in Linus's tree. Kees, did you also want this in the
> > -stable tree(s)?
>
> The potential problem was introduced with
> 4eefbe792baedb474e256d35370849992fcf1c79, so 3.10 needs it, yes. I had
> also sent a much smaller version here:
> http://git.kernel.org/cgit/linux/kernel/git/kees/linux.git/commit/?h=idt-stable&id=794c1e0df641e13050cfc4af340fc3c85bed4ea3
>
> Either will address the problem. If there is no problem with taking
> the larger clean-up for stable, then that's probably easiest.

I'd prefer to stick with what ended up in Linus's tree, so I'll just
queue this one up in a future stable 3.10 release, thanks.

greg k-h


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