Patch "MIPS: Disable preemption during prctl(PR_SET_FP_MODE, ...)" has been added to the 4.5-stable tree

[<gregkh@linuxfoundation.org>]

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

    MIPS: Disable preemption during prctl(PR_SET_FP_MODE, ...)

to the 4.5-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-disable-preemption-during-prctl-pr_set_fp_mode.patch
and it can be found in the queue-4.5 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 bd239f1e1429e7781096bf3884bdb1b2b1bb4f28 Mon Sep 17 00:00:00 2001
From: Paul Burton <paul.burton@imgtec.com>
Date: Thu, 21 Apr 2016 12:43:57 +0100
Subject: MIPS: Disable preemption during prctl(PR_SET_FP_MODE, ...)

From: Paul Burton <paul.burton@imgtec.com>

commit bd239f1e1429e7781096bf3884bdb1b2b1bb4f28 upstream.

Whilst a PR_SET_FP_MODE prctl is performed there are decisions made
based upon whether the task is executing on the current CPU. This may
change if we're preempted, so disable preemption to avoid such changes
for the lifetime of the mode switch.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Fixes: 9791554b45a2 ("MIPS,prctl: add PR_[GS]ET_FP_MODE prctl options for MIPS")
Reviewed-by: Maciej W. Rozycki <macro@imgtec.com>
Tested-by: Aurelien Jarno <aurelien@aurel32.net>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13144/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/kernel/process.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -601,6 +601,9 @@ int mips_set_process_fp_mode(struct task
 	if (!(value & PR_FP_MODE_FR) && cpu_has_fpu && cpu_has_mips_r6)
 		return -EOPNOTSUPP;
 
+	/* Proceed with the mode switch */
+	preempt_disable();
+
 	/* Save FP & vector context, then disable FPU & MSA */
 	if (task->signal == current->signal)
 		lose_fpu(1);
@@ -659,6 +662,7 @@ int mips_set_process_fp_mode(struct task
 
 	/* Allow threads to use FP again */
 	atomic_set(&task->mm->context.fp_mode_switching, 0);
+	preempt_enable();
 
 	return 0;
 }


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

queue-4.5/mips-disable-preemption-during-prctl-pr_set_fp_mode.patch
queue-4.5/mips-fix-sigreturn-via-vdso-on-micromips-kernel.patch
queue-4.5/mips-handle-highmem-pages-in-__update_cache.patch
queue-4.5/mips-fix-watchpoint-restoration.patch
queue-4.5/mips-build-micromips-vdso-for-micromips-kernels.patch
queue-4.5/mips-math-emu-fix-jalr-emulation-when-rd-0.patch
queue-4.5/mips-sync-icache-dcache-in-set_pte_at.patch
queue-4.5/mips-fix-msa-ld_-st_-asm-macros-to-use-ptr_addu.patch
queue-4.5/mips-prevent-restoration-of-msa-context-in-non-msa-kernels.patch
queue-4.5/mips-use-copy_s.fmt-rather-than-copy_u.fmt.patch