Patch "arm64: flush FP/SIMD state correctly after execve()" has been added to the 3.18-stable tree

Patch "arm64: flush FP/SIMD state correctly after execve()" has been added to the 3.18-stable tree

[gregkh]

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

    arm64: flush FP/SIMD state correctly after execve()

to the 3.18-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:
     arm64-flush-fp-simd-state-correctly-after-execve.patch
and it can be found in the queue-3.18 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 674c242c9323d3c293fc4f9a3a3a619fe3063290 Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date: Thu, 27 Aug 2015 07:12:33 +0100
Subject: arm64: flush FP/SIMD state correctly after execve()

From: Ard Biesheuvel <ard.biesheuvel@linaro.org>

commit 674c242c9323d3c293fc4f9a3a3a619fe3063290 upstream.

When a task calls execve(), its FP/SIMD state is flushed so that
none of the original program state is observeable by the incoming
program.

However, since this flushing consists of setting the in-memory copy
of the FP/SIMD state to all zeroes, the CPU field is set to CPU 0 as
well, which indicates to the lazy FP/SIMD preserve/restore code that
the FP/SIMD state does not need to be reread from memory if the task
is scheduled again on CPU 0 without any other tasks having entered
userland (or used the FP/SIMD in kernel mode) on the same CPU in the
mean time. If this happens, the FP/SIMD state of the old program will
still be present in the registers when the new program starts.

So set the CPU field to the invalid value of NR_CPUS when performing
the flush, by calling fpsimd_flush_task_state().

Reported-by: Chunyan Zhang <chunyan.zhang@spreadtrum.com>
Reported-by: Janet Liu <janet.liu@spreadtrum.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm64/kernel/fpsimd.c |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -157,6 +157,7 @@ void fpsimd_thread_switch(struct task_st
 void fpsimd_flush_thread(void)
 {
 	memset(&current->thread.fpsimd_state, 0, sizeof(struct fpsimd_state));
+	fpsimd_flush_task_state(current);
 	set_thread_flag(TIF_FOREIGN_FPSTATE);
 }
 


Patches currently in stable-queue which might be from ard.biesheuvel@linaro.org are

queue-3.18/arm64-flush-fp-simd-state-correctly-after-execve.patch
queue-3.18/arm64-fpsimd-prevent-registers-leaking-across-exec.patch