| Message ID | 20170923101733.kyq2avp6om2d2s3n@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
* Ingo Molnar <mingo@kernel.org> wrote: > > * Eric Biggers <ebiggers3@gmail.com> wrote: > > > On Fri, Sep 22, 2017 at 07:33:14AM +0200, Ingo Molnar wrote: > > > > > > * Eric Biggers <ebiggers3@gmail.com> wrote: > > > > > > > From: Eric Biggers <ebiggers@google.com> > > > > > > > > This series fixes the bug found by syzkaller where the ptrace syscall > > > > can be used to set invalid bits in a task's FPU state. I also found > > > > that an equivalent bug was reachable using the sigreturn syscall, so the > > > > first patch fixes the bug in both cases. > > > > > > > > The other two patches start validating the other parts of the > > > > xstate_header and make it so that invalid FPU states can no longer be > > > > abused to leak the FPU registers of other processes. > > > > > > > > Changes since v2: > > > > - Use an exception handler to handle invalid FPU states > > > > (suggested by Andy Lutomirski) > > > > - Check the size of xstate_header.reserved at build time > > > > (suggested by Dave Hansen) > > > > > > > > Eric Biggers (3): > > > > x86/fpu: don't let userspace set bogus xcomp_bv > > > > x86/fpu: tighten validation of user-supplied xstate_header > > > > x86/fpu: reinitialize FPU registers if restoring FPU state fails > > > > > > > > arch/x86/include/asm/fpu/internal.h | 51 +++++++++++-------------------------- > > > > arch/x86/include/asm/fpu/xstate.h | 25 ++++++++++++++++++ > > > > arch/x86/kernel/fpu/regset.c | 20 +++++++-------- > > > > arch/x86/kernel/fpu/signal.c | 15 ++++++++--- > > > > arch/x86/kernel/fpu/xstate.c | 27 ++++++++------------ > > > > arch/x86/mm/extable.c | 24 +++++++++++++++++ > > > > 6 files changed, 94 insertions(+), 68 deletions(-) > > > > > > Ok - could you please rebase these to to tip:master that is at: > > > > > > git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git master > > > > > > In particular this has a WIP.x86/fpu branch with FPU fixes+changes queued up but > > > not merged upstream (yet), which conflict with these changes. I'd like to merge > > > them all together. > > > > > > > Working on it, but there is a problem with current tip. PTRACE_GETREGSET is > > causing the following warning: > > Yes, the warning should be harmless, and I fixed it locally earlier today - does > the patch below solve it for you as well? Note that this fix is now part of tip:master as well, so if you re-test -tip you should get all the latest fixes as well (including yours!). Thanks, Ingo
On Sat, Sep 23, 2017 at 01:29:32PM +0200, Ingo Molnar wrote: > > > > > > > > Ok - could you please rebase these to to tip:master that is at: > > > > > > > > git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git master > > > > > > > > In particular this has a WIP.x86/fpu branch with FPU fixes+changes queued up but > > > > not merged upstream (yet), which conflict with these changes. I'd like to merge > > > > them all together. > > > > > > > > > > Working on it, but there is a problem with current tip. PTRACE_GETREGSET is > > > causing the following warning: > > > > Yes, the warning should be harmless, and I fixed it locally earlier today - does > > the patch below solve it for you as well? > > Note that this fix is now part of tip:master as well, so if you re-test -tip you > should get all the latest fixes as well (including yours!). > No issues so far with the latest tip/master (commit e7c6e3675331). Eric
============================> Subject: x86/fpu: Simplify fpu__activate_fpstate_read() From: Ingo Molnar <mingo@kernel.org> Date: Sat Sep 23 11:41:23 CEST 2017 fpu__activate_fpstate_read() can only ever be called for a non-current, non-executing (stopped) task - so make sure this is checked via a warning and remove the current-task logic. This also fixes an incorrect (but harmless) warning triggered by of the earlier patches. Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/kernel/fpu/core.c | 24 ++++++++---------------- 1 file changed, 8 insertions(+), 16 deletions(-) Index: linux/arch/x86/kernel/fpu/core.c =================================================================== --- linux.orig/arch/x86/kernel/fpu/core.c +++ linux/arch/x86/kernel/fpu/core.c @@ -256,26 +256,18 @@ EXPORT_SYMBOL_GPL(fpu__activate_curr); * * If the task has not used the FPU before then initialize its * fpstate. - * - * If the task has used the FPU before then save it. */ void fpu__activate_fpstate_read(struct fpu *fpu) { - /* - * If fpregs are active (in the current CPU), then - * copy them to the fpstate: - */ - if (fpu->fpstate_active) { - fpu__save(fpu); - } else { - if (!fpu->fpstate_active) { - fpstate_init(&fpu->state); - trace_x86_fpu_init_state(fpu); + WARN_ON_FPU(fpu == ¤t->thread.fpu); + + if (!fpu->fpstate_active) { + fpstate_init(&fpu->state); + trace_x86_fpu_init_state(fpu); - trace_x86_fpu_activate_state(fpu); - /* Safe to do for current and for stopped child tasks: */ - fpu->fpstate_active = 1; - } + trace_x86_fpu_activate_state(fpu); + /* Safe to do for current and for stopped child tasks: */ + fpu->fpstate_active = 1; } }