Patch "MIPS: ptrace: Fix FP context restoration FCSR regression" has been added to the 4.6-stable tree

Patch "MIPS: ptrace: Fix FP context restoration FCSR regression" has been added to the 4.6-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    MIPS: ptrace: Fix FP context restoration FCSR regression

to the 4.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mips-ptrace-fix-fp-context-restoration-fcsr-regression.patch
and it can be found in the queue-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 4249548454f7ba4581aeee26bd83f42b48a14d15 Mon Sep 17 00:00:00 2001
From: "Maciej W. Rozycki" <macro@imgtec.com>
Date: Thu, 12 May 2016 10:18:27 +0100
Subject: MIPS: ptrace: Fix FP context restoration FCSR regression

From: Maciej W. Rozycki <macro@imgtec.com>

commit 4249548454f7ba4581aeee26bd83f42b48a14d15 upstream.

Fix a floating-point context restoration regression introduced with
commit 9b26616c8d9d ("MIPS: Respect the ISA level in FCSR handling")
that causes a Floating Point exception and consequently a kernel oops
with hard float configurations when one or more FCSR Enable and their
corresponding Cause bits are set both at a time via a ptrace(2) call.

To do so reinstate Cause bit masking originally introduced with commit
b1442d39fac2 ("MIPS: Prevent user from setting FCSR cause bits") to
address this exact problem and then inadvertently removed from the
PTRACE_SETFPREGS request with the commit referred above.

Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13238/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/kernel/ptrace.c |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/mips/kernel/ptrace.c
+++ b/arch/mips/kernel/ptrace.c
@@ -176,6 +176,7 @@ int ptrace_setfpregs(struct task_struct
 	}
 
 	__get_user(value, data + 64);
+	value &= ~FPU_CSR_ALL_X;
 	fcr31 = child->thread.fpu.fcr31;
 	mask = boot_cpu_data.fpu_msk31;
 	child->thread.fpu.fcr31 = (value & ~mask) | (fcr31 & mask);


Patches currently in stable-queue which might be from macro@imgtec.com are

queue-4.6/mips-disable-preemption-during-prctl-pr_set_fp_mode.patch
queue-4.6/mips-ptrace-prevent-writes-to-read-only-fcsr-bits.patch
queue-4.6/mips-msa-fix-a-link-error-on-_init_msa_upper-with-older-gcc.patch
queue-4.6/mips-force-cpus-to-lose-fp-context-during-mode-switches.patch
queue-4.6/mips-ptrace-fix-fp-context-restoration-fcsr-regression.patch
queue-4.6/mips-vdso-build-with-fno-strict-aliasing.patch
queue-4.6/mips-math-emu-fix-jalr-emulation-when-rd-0.patch