• Yu-cheng Yu's avatar
    x86/fpu/xstate: Fix xcomp_bv in XSAVES header · dffba9a3
    Yu-cheng Yu authored
    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:
    
      b22cbe40 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
    others:
    
    	https://bugzilla.kernel.org/show_bug.cgi?id=190061
    
    Fix it by setting xcomp_bv correctly.
    
    This patch also moves the xcomp_bv initialization to the proper
    place, which was in copyin_to_xsaves() as of:
    
      4c833368 x86/fpu: Set the xcomp_bv when we fake up a XSAVES area
    
    which fixed the bug too, but it's more efficient and cleaner to
    initialize things once per boot, not for every signal handling
    operation.
    Reported-by: default avatarKevin Hao <haokexin@gmail.com>
    Reported-by: default avatarJoakim Tjernlund <Joakim.Tjernlund@infinera.com>
    Signed-off-by: default avatarYu-cheng Yu <yu-cheng.yu@intel.com>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Borislav Petkov <bp@suse.de>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: Fenghua Yu <fenghua.yu@intel.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: haokexin@gmail.com
    Link: http://lkml.kernel.org/r/1485212084-4418-1-git-send-email-yu-cheng.yu@intel.com
    [ Combined it with 4c833368. ]
    Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    dffba9a3
xstate.c 28.3 KB