4.2-stable review patch. If anyone has any objections, please let me know.
------------------
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
@@ -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 stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html