Copy real FS/GSBASE values instead of approximation when FSGSBASE is enabled.
Suggested-by: Andy Lutomirski <[email protected]> Signed-off-by: Chang S. Bae <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Andi Kleen <[email protected]> --- arch/x86/kernel/process_64.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index d3abe4748d8b..c4de0907d909 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -422,7 +422,8 @@ unsigned long x86_fsbase_read_task(struct task_struct *task) if (task == current) fsbase = x86_fsbase_read_cpu(); - else if (task->thread.fsindex == 0) + else if (static_cpu_has(X86_FEATURE_FSGSBASE) || + (task->thread.fsindex == 0)) fsbase = task->thread.fsbase; else fsbase = x86_fsgsbase_read_task(task, task->thread.fsindex); @@ -436,7 +437,8 @@ unsigned long x86_gsbase_read_task(struct task_struct *task) if (task == current) gsbase = x86_gsbase_read_cpu_inactive(); - else if (task->thread.gsindex == 0) + else if (static_cpu_has(X86_FEATURE_FSGSBASE) || + (task->thread.gsindex == 0)) gsbase = task->thread.gsbase; else gsbase = x86_fsgsbase_read_task(task, task->thread.gsindex); @@ -475,10 +477,11 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp, p->thread.sp = (unsigned long) fork_frame; p->thread.io_bitmap_ptr = NULL; - savesegment(gs, p->thread.gsindex); - p->thread.gsbase = p->thread.gsindex ? 0 : me->thread.gsbase; - savesegment(fs, p->thread.fsindex); - p->thread.fsbase = p->thread.fsindex ? 0 : me->thread.fsbase; + save_fsgs(me); + p->thread.fsindex = me->thread.fsindex; + p->thread.fsbase = me->thread.fsbase; + p->thread.gsindex = me->thread.gsindex; + p->thread.gsbase = me->thread.gsbase; savesegment(es, p->thread.es); savesegment(ds, p->thread.ds); memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); -- 2.19.1
