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x86/fpu: Emulate XRSTOR's behavior if the xfeatures PKRU bit is not set

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commit d7e5aceace upstream

The hardware XRSTOR instruction resets the PKRU register to its hardware
init value (namely 0) if the PKRU bit is not set in the xfeatures mask.
Emulating that here restores the pre-5.14 behavior for PTRACE_SET_REGSET
with NT_X86_XSTATE, and makes sigreturn (which still uses XRSTOR) and
behave identically.

Fixes: e84ba47e31 ("x86/fpu: Hook up PKRU into ptrace()")
Signed-off-by: Kyle Huey <me@kylehuey.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20221115230932.7126-6-khuey%40kylehuey.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Kyle Huey
2023-01-09 13:02:13 -08:00
committed by Greg Kroah-Hartman
parent 3f1c81426a
commit 3c1940c549
1 changed files with 2 additions and 1 deletions
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3
arch/x86/kernel/fpu/xstate.c
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@@ -1168,7 +1168,8 @@ static int copy_uabi_to_xstate(struct xregs_state *xsave, const void *kbuf,
xpkru = __raw_xsave_addr(xsave, XFEATURE_PKRU);
*pkru = xpkru->pkru;
}
} else
*pkru = 0;
/*
* The state that came in from userspace was user-state only.