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@xxxxxxxxxxxxxxx> know about it.
>From 674c242c9323d3c293fc4f9a3a3a619fe3063290 Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Date: Thu, 27 Aug 2015 07:12:33 +0100
Subject: arm64: flush FP/SIMD state correctly after execve()
From: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
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@xxxxxxxxxxxxxx>
Reported-by: Janet Liu <janet.liu@xxxxxxxxxxxxxx>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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(¤t->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@xxxxxxxxxx are
queue-3.18/arm64-flush-fp-simd-state-correctly-after-execve.patch
queue-3.18/arm64-fpsimd-prevent-registers-leaking-across-exec.patch