| From | Kamal Mostafa <> | Subject | [PATCH 3.19.y-ckt 074/156] arm64: flush FP/SIMD state correctly after execve() | Date | Tue, 20 Oct 2015 14:36:55 -0700 |
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3.19.8-ckt8 -stable review patch. If anyone has any objections, please let me know.
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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: Kamal Mostafa <kamal@canonical.com> --- arch/arm64/kernel/fpsimd.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 3dca156..c31e59f 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -157,6 +157,7 @@ void fpsimd_thread_switch(struct task_struct *next) 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); } -- 1.9.1
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