From: Ard Biesheuvel Date: Thu, 27 Aug 2015 06:12:33 +0000 (+0100) Subject: arm64: flush FP/SIMD state correctly after execve() X-Git-Tag: v3.18.69~7 X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f5b150b99bf0aa09e0fabc36e599cae14eb5b66c;p=linux arm64: flush FP/SIMD state correctly after execve() 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 Reported-by: Janet Liu Signed-off-by: Ard Biesheuvel Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 3dca15634e69..c31e59fe2cb8 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); }