On Thu, Apr 23, 2015 at 10:15 PM, Andy Lutomirski <l...@kernel.org> wrote: > AMD CPUs don't reinitialize the SS descriptor on SYSRET, so SYSRET > with SS == 0 results in an invalid usermode state in which SS is > apparently equal to __USER_DS but causes #SS if used. > > Work around the issue by replacing NULL SS values with __KERNEL_DS > in __switch_to, thus ensuring that SYSRET never happens with SS set > to NULL. > > This was exposed by a recent vDSO cleanup. > > Fixes: e7d6eefaaa44 x86/vdso32/syscall.S: Do not load __USER32_DS to %ss > Signed-off-by: Andy Lutomirski <l...@kernel.org> > --- > > Tested only on Intel, which isn't very interesting. I'll tidy up > and send a test case, too, once Borislav confirms that it works. > > Please don't actually apply this until we're sure we understand the > scope of the issue. If this doesn't affect SYSRETQ, then we might > to fix it on before SYSRETL to avoid impacting 64-bit processes > at all.
It works with Wine. Tested on an AMD Phenom II. -- Brian Gerst -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
