lkml.org 
[lkml]   [2018]   [Oct]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [RFC PATCH v4 06/27] x86/cet: Control protection exception handler
    From
    Date
    On Wed, 2018-10-03 at 12:39 +0200, Eugene Syromiatnikov wrote:
    > On Fri, Sep 21, 2018 at 08:03:30AM -0700, Yu-cheng Yu wrote:
    > > +dotraplinkage void
    > > +do_control_protection(struct pt_regs *regs, long error_code)
    > > +{
    > > + struct task_struct *tsk;
    > > +
    > > + RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
    > > + if (notify_die(DIE_TRAP, "control protection fault", regs,
    > > + error_code, X86_TRAP_CP, SIGSEGV) == NOTIFY_STOP)
    > > + return;
    > > + cond_local_irq_enable(regs);
    > > +
    > > + if (!user_mode(regs))
    > > + die("kernel control protection fault", regs, error_code);
    > > +
    > > + if (!static_cpu_has(X86_FEATURE_SHSTK) &&
    > > + !static_cpu_has(X86_FEATURE_IBT))
    > > + WARN_ONCE(1, "CET is disabled but got control "
    > > + "protection fault\n");
    > > +
    > > + tsk = current;
    > > + tsk->thread.error_code = error_code;
    > > + tsk->thread.trap_nr = X86_TRAP_CP;
    > > +
    > > + if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
    > > + printk_ratelimit()) {
    > > + unsigned int max_err;
    > > +
    > > + max_err = ARRAY_SIZE(control_protection_err) - 1;
    > > + if ((error_code < 0) || (error_code > max_err))
    > > + error_code = 0;
    > > + pr_info("%s[%d] control protection ip:%lx sp:%lx
    > > error:%lx(%s)",
    > > + tsk->comm, task_pid_nr(tsk),
    > > + regs->ip, regs->sp, error_code,
    > > + control_protection_err[error_code]);
    > > + print_vma_addr(KERN_CONT " in ", regs->ip);
    > > + pr_cont("\n");
    > > + }
    > > +
    > > + force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
    >
    > That way, no information is provided to userspace (both application and
    > debugger), which is rather unfortunate. It would be nice if a new SEGV_*
    > code was added at least, and CET error (with error code constant provided
    > in UAPI) is passed via si_errno. (Having ip/sp/*ssp would be even
    > better, but I'm not exactly sure about ramifications of providing this
    > kind of information to user space).

    Ok, I will add that.

    Yu-cheng

    \
     
     \ /
      Last update: 2018-10-03 18:22    [W:6.636 / U:0.040 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site