Re: [tip:x86/urgent] x86/fpu/xstate: Fix xcomp_bv in XSAVES header
From: Yu-cheng Yu
Date: Tue Feb 14 2017 - 16:31:12 EST
On Tue, Jan 24, 2017 at 12:46:17AM -0800, tip-bot for Yu-cheng Yu wrote:
> Commit-ID: dffba9a31c7769be3231c420d4b364c92ba3f1ac
> Gitweb: http://git.kernel.org/tip/dffba9a31c7769be3231c420d4b364c92ba3f1ac
> Author: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
> AuthorDate: Mon, 23 Jan 2017 14:54:44 -0800
> Committer: Ingo Molnar <mingo@xxxxxxxxxx>
> CommitDate: Tue, 24 Jan 2017 09:04:48 +0100
> x86/fpu/xstate: Fix xcomp_bv in XSAVES header
> The compacted-format XSAVES area is determined at boot time and
> never changed after. The field xsave.header.xcomp_bv indicates
> which components are in the fixed XSAVES format.
> In fpstate_init() we did not set xcomp_bv to reflect the XSAVES
> format since at the time there is no valid data.
> However, after we do copy_init_fpstate_to_fpregs() in fpu__clear(),
> as in commit:
> b22cbe404a9c x86/fpu: Fix invalid FPU ptrace state after execve()
> and when __fpu_restore_sig() does fpu__restore() for a COMPAT-mode
> app, a #GP occurs. This can be easily triggered by doing valgrind on
> a COMPAT-mode "Hello World," as reported by Joakim Tjernlund and
> Fix it by setting xcomp_bv correctly.
Please consider pulling this into the stable tree because my previous
patch in commit:
b22cbe404a9c x86/fpu: Fix invalid FPU ptrace state after execve()
exposes the same issue in the stable tree.