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linux/arch/x86/kernel/fpu
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Yu-cheng Yu dffba9a31c 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:

  b22cbe404a 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:

  4c833368f0 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: Kevin Hao <haokexin@gmail.com>
Reported-by: Joakim Tjernlund <Joakim.Tjernlund@infinera.com>
Signed-off-by: Yu-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 4c833368f0. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-01-24 09:04:48 +01:00
..
bugs.c x86/fpu: Stop saving and restoring CR0.TS in fpu__init_check_bugs() 2016-11-01 07:47:53 +01:00
core.c x86/fpu/xstate: Fix xcomp_bv in XSAVES header 2017-01-24 09:04:48 +01:00
init.c x86/fpu: Get rid of two redundant clts() calls 2016-11-01 07:47:53 +01:00
Makefile
regset.c x86/fpu/xstate: Fix PTRACE frames for XSAVES 2016-07-10 17:12:10 +02:00
signal.c x86/fpu: Remove use_eager_fpu() 2016-10-07 11:14:36 +02:00
xstate.c x86/fpu/xstate: Fix xcomp_bv in XSAVES header 2017-01-24 09:04:48 +01:00