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Date: Sat, 26 Sep 2015 13:54:41 -0700 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Chunyan Zhang <chunyan.zhang@...eadtrum.com>, Janet Liu <janet.liu@...eadtrum.com>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, Will Deacon <will.deacon@....com> Subject: [PATCH 4.2 029/134] arm64: flush FP/SIMD state correctly after execve() 4.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ard Biesheuvel <ard.biesheuvel@...aro.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@...eadtrum.com> Reported-by: Janet Liu <janet.liu@...eadtrum.com> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org> Signed-off-by: Will Deacon <will.deacon@....com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- arch/arm64/kernel/fpsimd.c | 1 + 1 file changed, 1 insertion(+) --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -158,6 +158,7 @@ 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); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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