Commit 674c242c authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Will Deacon

arm64: flush FP/SIMD state correctly after execve()

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().

Cc: <stable@vger.kernel.org>
Reported-by: default avatarChunyan Zhang <chunyan.zhang@spreadtrum.com>
Reported-by: default avatarJanet Liu <janet.liu@spreadtrum.com>
Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 5166c20e
...@@ -158,6 +158,7 @@ void fpsimd_thread_switch(struct task_struct *next) ...@@ -158,6 +158,7 @@ void fpsimd_thread_switch(struct task_struct *next)
void fpsimd_flush_thread(void) void fpsimd_flush_thread(void)
{ {
memset(&current->thread.fpsimd_state, 0, sizeof(struct fpsimd_state)); memset(&current->thread.fpsimd_state, 0, sizeof(struct fpsimd_state));
fpsimd_flush_task_state(current);
set_thread_flag(TIF_FOREIGN_FPSTATE); set_thread_flag(TIF_FOREIGN_FPSTATE);
} }
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment