Messages in this thread |  | | | Date | Sat, 26 Jul 2008 16:37:56 +0200 | | From | Ingo Molnar <> | | Subject | Re: [patch] x64, fpu: fix possible FPU leakage in error conditions |
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* Suresh Siddha <suresh.b.siddha@intel.com> wrote:
> On Thu, Jul 24, 2008 at 03:43:44PM -0700, Linus Torvalds wrote: > > So how about this patch as a starting point? This is the RightThing(tm) to > > do regardless, and if it then makes it easier to do some other cleanups, > > we should do it first. What do you think? > > Linus, Attached is my last attempt for the day. Please review. Thanks. > --- > > restore_fpu_checking() calls init_fpu() in error conditions. While > this is wrong(as our main intention is to clear the fpu state of the > thread), this was benign before the commit > 92d140e21f1ce8cf99320afbbcad73879128e6dc. > > Post commit 92d140e21f1ce8cf99320afbbcad73879128e6dc, live FPU > registers may not belong to this process at this error scenario. > > In the error condition for restore_fpu_checking() (especially during > the 64bit signal return), we are doing init_fpu(), which saves the > live FPU register state (possibly belonging to some other process > context) into the thread struct (through unlazy_fpu() in init_fpu()). > This is wrong and can leak the FPU data. > > For the signal handler restore error condition in restore_i387(), > clear the fpu state present in the thread struct(before ultimately > sending a SIGSEGV for badframe). > > For the paranoid error condition check in math_state_restore(), send a > SIGSEGV, if we fail to restore the state.
i've applied your patch to tip/x86/fpu for further testing. I suspect once it proves reliable we can merge it into v2.6.27, after -rc1.
Ingo
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