x86/fpu: Mop up xfeatures_mask_uabi()

Use the new fpu_user_cfg to retrieve the information instead of
xfeatures_mask_uabi() which will be no longer correct when dynamically
enabled features become available.

Using fpu_user_cfg is appropriate when setting XCOMP_BV in the
init_fpstate since it has space allocated for "max_features". But,
normal fpstates might only have space for default xfeatures. Since
XRSTOR* derives the format of the XSAVE buffer from XCOMP_BV, this can
lead to XRSTOR reading out of bounds.

So when copying actively used fpstate, simply read the XCOMP_BV features
bits directly out of the fpstate instead.

This correction courtesy of Dave Hansen <dave.hansen@linux.intel.com>

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211014230739.408879849@linutronix.de

1 files changed, 0 insertions, 9 deletions

diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index fe7c9af9ea42..3c890b97f195 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -84,15 +84,6 @@ static inline u64 xfeatures_mask_supervisor(void)
 }
 
 /*
- * The xfeatures which are enabled in XCR0 and expected to be in ptrace
- * buffers and signal frames.
- */
-static inline u64 xfeatures_mask_uabi(void)
-{
-	return fpu_kernel_cfg.max_features & XFEATURE_MASK_USER_SUPPORTED;
-}
-
-/*
  * The xfeatures which are restored by the kernel when returning to user
  * mode. This is not necessarily the same as xfeatures_mask_uabi() as the
  * kernel does not manage all XCR0 enabled features via xsave/xrstor as