| From | Andrei Vagin <> | Date | Wed, 13 Jul 2022 21:04:02 -0700 | Subject | Re: [patch V4 09/65] x86/fpu: Sanitize xstateregs_set() |
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On Wed, Jun 23, 2021 at 5:24 AM Thomas Gleixner <tglx@linutronix.de> wrote: .... > > - /* > - * mxcsr reserved bits must be masked to zero for security reasons. > - */ > - xsave->i387.mxcsr &= mxcsr_feature_mask; > - > - /* > - * In case of failure, mark all states as init: > - */ > - if (ret) > - fpstate_init(&fpu->state); > + fpu__prepare_write(fpu); > + ret = copy_kernel_to_xstate(&fpu->state.xsave, kbuf ?: tmpbuf);
This change breaks gVisor. Now, when we set a new fpu state without fp,sse and ymm via ptrace, mxcsr isn't reset to the default value. The issue is reproduced only on hosts without xsaves. On hosts with xsaves, it works as expected.
Thanks, Andrei
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