Messages in this thread | | | Subject | Re: [PATCH] x86/split_lock: Sanitize userspace and guest error output | From | Xiaoyao Li <> | Date | Fri, 5 Jun 2020 23:29:57 +0800 |
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On 6/5/2020 7:44 PM, Prarit Bhargava wrote: > There are two problems with kernel messages in fatal mode that > were found during testing of guests and userspace programs. > > The first is that no kernel message is output when the split lock detector > is triggered with a userspace program. As a result the userspace process > dies from receiving SIGBUS with no indication to the user of what caused > the process to die. > > The second problem is that only the first triggering guest causes a kernel > message to be output because the message is output with pr_warn_once(). > This also results in a loss of information to the user. > > While fixing these I noticed that the same message was being output > three times so I'm cleaning that up too. > > Fix fatal mode output, and use consistent messages for fatal and > warn modes for both userspace and guests. > > Signed-off-by: Prarit Bhargava <prarit@redhat.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Borislav Petkov <bp@alien8.de> > Cc: x86@kernel.org > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: Tony Luck <tony.luck@intel.com> > Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org> > Cc: Sean Christopherson <sean.j.christopherson@intel.com> > Cc: Rahul Tanwar <rahul.tanwar@linux.intel.com> > Cc: Xiaoyao Li <xiaoyao.li@intel.com> > Cc: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> > Cc: Dave Hansen <dave.hansen@linux.intel.com> > --- > arch/x86/kernel/cpu/intel.c | 24 ++++++++++-------------- > 1 file changed, 10 insertions(+), 14 deletions(-) > > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c > index 166d7c355896..463022aa9b7a 100644 > --- a/arch/x86/kernel/cpu/intel.c > +++ b/arch/x86/kernel/cpu/intel.c > @@ -1074,10 +1074,14 @@ static void split_lock_init(void) > split_lock_verify_msr(sld_state != sld_off); > } > > -static void split_lock_warn(unsigned long ip) > +static bool split_lock_warn(unsigned long ip, int fatal) > { > - pr_warn_ratelimited("#AC: %s/%d took a split_lock trap at address: 0x%lx\n", > - current->comm, current->pid, ip); > + pr_warn_ratelimited("#AC: %s/%d %ssplit_lock trap at address: 0x%lx\n", > + current->comm, current->pid, > + sld_state == sld_fatal ? "fatal " : "", ip); > + > + if (sld_state == sld_fatal || fatal) > + return false; > > /* > * Disable the split lock detection for this task so it can make > @@ -1086,18 +1090,13 @@ static void split_lock_warn(unsigned long ip) > */ > sld_update_msr(false); > set_tsk_thread_flag(current, TIF_SLD); > + return true; > } > > bool handle_guest_split_lock(unsigned long ip) > { > - if (sld_state == sld_warn) { > - split_lock_warn(ip); > + if (split_lock_warn(ip, 0)) > return true; > - } > - > - pr_warn_once("#AC: %s/%d %s split_lock trap at address: 0x%lx\n", > - current->comm, current->pid, > - sld_state == sld_fatal ? "fatal" : "bogus", ip); > > current->thread.error_code = 0; > current->thread.trap_nr = X86_TRAP_AC; > @@ -1108,10 +1107,7 @@ EXPORT_SYMBOL_GPL(handle_guest_split_lock); > > bool handle_user_split_lock(struct pt_regs *regs, long error_code) > { > - if ((regs->flags & X86_EFLAGS_AC) || sld_state == sld_fatal) > - return false; > - split_lock_warn(regs->ip); > - return true; > + return split_lock_warn(regs->ip, regs->flags & X86_EFLAGS_AC);
It's incorrect. You change the behavior that it will print the split lock warning even when CPL 3 Alignment Check is turned on.
> } > > /* >
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