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Peter Anvin" , Thomas Gleixner , Ingo Molnar , Dave Hansen , Tony Luck , Andy Lutomirski , Rik van Riel , "Ravi V. Shankar" , Sebastian Andrzej Siewior , Fenghua Yu , Peter Zijlstra Subject: Re: [PATCH v2 6/8] x86/fpu/xstate: Update sanitize_restored_xstate() for supervisor xstates Message-ID: <20200221143010.GH25747@zn.tnic> References: <20200121201843.12047-1-yu-cheng.yu@intel.com> <20200121201843.12047-7-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200121201843.12047-7-yu-cheng.yu@intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 21, 2020 at 12:18:41PM -0800, Yu-cheng Yu wrote: > The function sanitize_restored_xstate() sanitizes user xstates of an XSAVE > buffer by setting the buffer's header->xfeatures to the input 'xfeatures', > effectively resetting features not in 'xfeatures' back to the init state. > > When supervisor xstates are introduced, it is necessary to make sure only > user xstates are sanitized. This patch ensures supervisor xstates are not Avoid having "This patch" or "This commit" in the commit message. It is tautologically useless. Also, do $ git grep 'This patch' Documentation/process for more details. > changed by ensuring supervisor bits stay set in header->xfeatures. > > To make names clear, also: > > - Rename the function to sanitize_restored_user_xstate(). > - Rename input parameter 'xfeatures' to 'xfeatures_from_user'. > - In __fpu__restore_sig(), rename 'xfeatures' to 'xfeatures_user'. Call them all "user_xfeatures" to differentiate that it is a function argument and not our xfeature_* macro and function names. > Signed-off-by: Yu-cheng Yu > Reviewed-by: Dave Hansen > --- > arch/x86/kernel/fpu/signal.c | 37 +++++++++++++++++++++++------------- > 1 file changed, 24 insertions(+), 13 deletions(-) > > diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c > index 4afe61987e03..e3781a4a52a8 100644 > --- a/arch/x86/kernel/fpu/signal.c > +++ b/arch/x86/kernel/fpu/signal.c > @@ -211,9 +211,9 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size) > } > > static inline void > -sanitize_restored_xstate(union fpregs_state *state, > - struct user_i387_ia32_struct *ia32_env, > - u64 xfeatures, int fx_only) > +sanitize_restored_user_xstate(union fpregs_state *state, > + struct user_i387_ia32_struct *ia32_env, > + u64 xfeatures_from_user, int fx_only) > { > struct xregs_state *xsave = &state->xsave; > struct xstate_header *header = &xsave->header; > @@ -226,13 +226,22 @@ sanitize_restored_xstate(union fpregs_state *state, > */ > > /* > - * Init the state that is not present in the memory > - * layout and not enabled by the OS. > + * 'xfeatures_from_user' might have bits clear which are > + * set in header->xfeatures. This represents features that > + * were in init state prior to a signal delivery, and need > + * to be reset back to the init state. Clear any user > + * feature bits which are set in the kernel buffer to get > + * them back to the init state. > + * > + * Supervisor state is unchanged by input from userspace. > + * Ensure that supervisor state is not modified by ensuring > + * supervisor state bits stay set. "Ensure ... by ensuring ..." Simplify pls. > */ > if (fx_only) > header->xfeatures = XFEATURE_MASK_FPSSE; > else > - header->xfeatures &= xfeatures; > + header->xfeatures &= xfeatures_from_user | > + xfeatures_mask_supervisor(); > } > > if (use_fxsr()) { -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette