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x86/mm, tracing: Fix CR2 corruption

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Despite the current efforts to read CR2 before tracing happens there still
exist a number of possible holes:

  idtentry page_fault             do_page_fault           has_error_code=1
    call error_entry
      TRACE_IRQS_OFF
        call trace_hardirqs_off*
          #PF // modifies CR2

      CALL_enter_from_user_mode
        __context_tracking_exit()
          trace_user_exit(0)
            #PF // modifies CR2

    call do_page_fault
      address = read_cr2(); /* whoopsie */

And similar for i386.

Fix it by pulling the CR2 read into the entry code, before any of that
stuff gets a chance to run and ruin things.

Reported-by: He Zhe <zhe.he@windriver.com>
Reported-by: Eiichi Tsukata <devel@etsukata.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: bp@alien8.de
Cc: rostedt@goodmis.org
Cc: torvalds@linux-foundation.org
Cc: hpa@zytor.com
Cc: dave.hansen@linux.intel.com
Cc: jgross@suse.com
Cc: joel@joelfernandes.org
Link: https://lkml.kernel.org/r/20190711114336.116812491@infradead.org

Debugged-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Peter Zijlstra
2019-07-11 13:40:59 +02:00
committed by Thomas Gleixner
parent 4234653e88
commit a0d14b8909
7 changed files with 59 additions and 51 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
arch/x86/kernel/kvm.c
View File

@@ -242,23 +242,23 @@ EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason);
NOKPROBE_SYMBOL(kvm_read_and_reset_pf_reason);
dotraplinkage void
do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
do_async_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address)
{
enum ctx_state prev_state;
switch (kvm_read_and_reset_pf_reason()) {
default:
do_page_fault(regs, error_code);
do_page_fault(regs, error_code, address);
break;
case KVM_PV_REASON_PAGE_NOT_PRESENT:
/* page is swapped out by the host. */
prev_state = exception_enter();
kvm_async_pf_task_wait((u32)read_cr2(), !user_mode(regs));
kvm_async_pf_task_wait((u32)address, !user_mode(regs));
exception_exit(prev_state);
break;
case KVM_PV_REASON_PAGE_READY:
rcu_irq_enter();
kvm_async_pf_task_wake((u32)read_cr2());
kvm_async_pf_task_wake((u32)address);
rcu_irq_exit();
break;
}