From: "Chang S. Bae" <chang.seok....@intel.com> When FSGSBASE is enabled, copying threads and reading fsbase and gsbase using ptrace must read the actual values.
When copying a thread, use save_fsgs() and copy the saved values. For ptrace, the bases must be read from memory regardless of the selector if FSGSBASE is enabled. [ tglx: Invoke __rdgsbase_inactive() with interrupts disabled ] [ luto: Massage changelog ] Suggested-by: Andy Lutomirski <l...@kernel.org> Signed-off-by: Chang S. Bae <chang.seok....@intel.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Cc: "H . Peter Anvin" <h...@zytor.com> Cc: Andi Kleen <a...@linux.intel.com> Cc: Ravi Shankar <ravi.v.shan...@intel.com> Cc: H. Peter Anvin <h...@zytor.com> Link: https://lkml.kernel.org/r/1557309753-24073-9-git-send-email-chang.seok....@intel.com Signed-off-by: Sasha Levin <sas...@kernel.org> --- arch/x86/kernel/process.c | 10 ++++++---- arch/x86/kernel/process_64.c | 6 ++++-- 2 files changed, 10 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 9da70b279dad..0264d9bb8991 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -140,10 +140,12 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp, memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); #ifdef CONFIG_X86_64 - savesegment(gs, p->thread.gsindex); - p->thread.gsbase = p->thread.gsindex ? 0 : current->thread.gsbase; - savesegment(fs, p->thread.fsindex); - p->thread.fsbase = p->thread.fsindex ? 0 : current->thread.fsbase; + current_save_fsgs(); + p->thread.fsindex = current->thread.fsindex; + p->thread.fsbase = current->thread.fsbase; + p->thread.gsindex = current->thread.gsindex; + p->thread.gsbase = current->thread.gsbase; + savesegment(es, p->thread.es); savesegment(ds, p->thread.ds); #else diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index aefb30bc56bc..0bcb48a1264a 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -423,7 +423,8 @@ 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); @@ -437,7 +438,8 @@ 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); -- 2.25.1
