On Mon, Dec 22, 2014 at 12:08 PM, Dave Hansen <[email protected]> wrote: > > From: Dave Hansen <[email protected]> > > We had originally planned on submitting MPX support in one patch > set. We eventually broke it up in to two pieces for easier > review. One of the features that didn't make the first round > was supporting 32-bit binaries on 64-bit kernels. > > Once we split the set up, we never added code to restrict 32-bit > binaries from _using_ MPX on 64-bit kernels. > > The 32-bit bounds tables are a different format than the 64-bit > ones. Without this patch, the kernel will try to read a 32-bit > binary's tables as if they were the 64-bit version. They will > likely be noticed as being invalid rather quickly and the app > will get killed, but that's kinda mean. > > This patch adds an explicit check, and will make a 64-bit kernel > essentially behave as if it has no MPX support when called from > a 32-bit binary. > > I intend to remove this check once the mixed binary support is > added. Those patches are posted if anyone is interested: > > https://lkml.org/lkml/2014/12/12/632 > > Signed-off-by: Dave Hansen <[email protected]> > Cc: Andy Lutomirski <[email protected]> > --- > > b/arch/x86/mm/mpx.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff -puN > arch/x86/mm/mpx.c~x86-mpx-explicitly-disable-32-bit-on-64-bit-for-3_19 > arch/x86/mm/mpx.c > --- a/arch/x86/mm/mpx.c~x86-mpx-explicitly-disable-32-bit-on-64-bit-for-3_19 > 2014-12-22 12:06:18.308911687 -0800 > +++ b/arch/x86/mm/mpx.c 2014-12-22 12:06:18.311911822 -0800 > @@ -349,6 +349,12 @@ static __user void *task_get_bounds_dir( > return MPX_INVALID_BOUNDS_DIR; > > /* > + * 32-bit binaries on 64-bit kernels are currently > + * unsupported. > + */ > + if (IS_ENABLED(CONFIG_X86_64) && test_thread_flag(TIF_IA32)) > + return MPX_INVALID_BOUNDS_DIR;
Should this check mm->ia32_compat instead? Otherwise, Reviewed-by: Andy Lutomirski <[email protected]> > + /* > * The bounds directory pointer is stored in a register > * only accessible if we first do an xsave. > */ > _ -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
