From d11994314b2bfe028bc39be24b44298787925160 Mon Sep 17 00:00:00 2001 From: Cyril Bur Date: Fri, 23 Sep 2016 16:18:12 +1000 Subject: powerpc: signals: Stop using current in signal code Much of the signal code takes a pt_regs on which it operates. Over time the signal code has needed to know more about the thread than what pt_regs can supply, this information is obtained as needed by using 'current'. This approach is not strictly incorrect however it does mean that there is now a hard requirement that the pt_regs being passed around does belong to current, this is never checked. A safer approach is for the majority of the signal functions to take a task_struct from which they can obtain pt_regs and any other information they need. The caveat that the task_struct they are passed must be current doesn't go away but can more easily be checked for. Functions called from outside powerpc signal code are passed a pt_regs and they can confirm that the pt_regs is that of current and pass current to other functions, furthurmore, powerpc signal functions can check that the task_struct they are passed is the same as current avoiding possible corruption of current (or the task they are passed) if this assertion ever fails. CC: paulus@samba.org Signed-off-by: Cyril Bur Signed-off-by: Michael Ellerman --- arch/powerpc/kernel/signal.c | 41 +++++++++++++++++++++++------------------ 1 file changed, 23 insertions(+), 18 deletions(-) (limited to 'arch/powerpc/kernel/signal.c') diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c index cb64d6feb45a..bbe77aed198d 100644 --- a/arch/powerpc/kernel/signal.c +++ b/arch/powerpc/kernel/signal.c @@ -99,22 +99,24 @@ static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka, } } -static void do_signal(struct pt_regs *regs) +static void do_signal(struct task_struct *tsk) { sigset_t *oldset = sigmask_to_save(); struct ksignal ksig; int ret; int is32 = is_32bit_task(); + BUG_ON(tsk != current); + get_signal(&ksig); /* Is there any syscall restart business here ? */ - check_syscall_restart(regs, &ksig.ka, ksig.sig > 0); + check_syscall_restart(tsk->thread.regs, &ksig.ka, ksig.sig > 0); if (ksig.sig <= 0) { /* No signal to deliver -- put the saved sigmask back */ restore_saved_sigmask(); - regs->trap = 0; + tsk->thread.regs->trap = 0; return; /* no signals delivered */ } @@ -124,23 +126,22 @@ static void do_signal(struct pt_regs *regs) * user space. The DABR will have been cleared if it * triggered inside the kernel. */ - if (current->thread.hw_brk.address && - current->thread.hw_brk.type) - __set_breakpoint(¤t->thread.hw_brk); + if (tsk->thread.hw_brk.address && tsk->thread.hw_brk.type) + __set_breakpoint(&tsk->thread.hw_brk); #endif /* Re-enable the breakpoints for the signal stack */ - thread_change_pc(current, regs); + thread_change_pc(tsk, tsk->thread.regs); if (is32) { if (ksig.ka.sa.sa_flags & SA_SIGINFO) - ret = handle_rt_signal32(&ksig, oldset, regs); + ret = handle_rt_signal32(&ksig, oldset, tsk); else - ret = handle_signal32(&ksig, oldset, regs); + ret = handle_signal32(&ksig, oldset, tsk); } else { - ret = handle_rt_signal64(&ksig, oldset, regs); + ret = handle_rt_signal64(&ksig, oldset, tsk); } - regs->trap = 0; + tsk->thread.regs->trap = 0; signal_setup_done(ret, &ksig, test_thread_flag(TIF_SINGLESTEP)); } @@ -151,8 +152,10 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags) if (thread_info_flags & _TIF_UPROBE) uprobe_notify_resume(regs); - if (thread_info_flags & _TIF_SIGPENDING) - do_signal(regs); + if (thread_info_flags & _TIF_SIGPENDING) { + BUG_ON(regs != current->thread.regs); + do_signal(current); + } if (thread_info_flags & _TIF_NOTIFY_RESUME) { clear_thread_flag(TIF_NOTIFY_RESUME); @@ -162,7 +165,7 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags) user_enter(); } -unsigned long get_tm_stackpointer(struct pt_regs *regs) +unsigned long get_tm_stackpointer(struct task_struct *tsk) { /* When in an active transaction that takes a signal, we need to be * careful with the stack. It's possible that the stack has moved back @@ -187,11 +190,13 @@ unsigned long get_tm_stackpointer(struct pt_regs *regs) */ #ifdef CONFIG_PPC_TRANSACTIONAL_MEM - if (MSR_TM_ACTIVE(regs->msr)) { + BUG_ON(tsk != current); + + if (MSR_TM_ACTIVE(tsk->thread.regs->msr)) { tm_reclaim_current(TM_CAUSE_SIGNAL); - if (MSR_TM_TRANSACTIONAL(regs->msr)) - return current->thread.ckpt_regs.gpr[1]; + if (MSR_TM_TRANSACTIONAL(tsk->thread.regs->msr)) + return tsk->thread.ckpt_regs.gpr[1]; } #endif - return regs->gpr[1]; + return tsk->thread.regs->gpr[1]; } -- cgit v1.2.3