x86/ldt: Make LDT pgtable free conditional

Andy prefers to be paranoid about the pagetable free in the error path of
write_ldt(). Make it conditional and warn whenever the installment of a
secondary LDT fails.

Requested-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c
index 500e90e44f86..26d713ecad34 100644
--- a/arch/x86/kernel/ldt.c
+++ b/arch/x86/kernel/ldt.c
@@ -426,7 +426,8 @@ static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode)
                  * already installed then the PTE page is already
                  * populated. Mop up a half populated page table.
                  */
-                free_ldt_pgtables(mm);
+                if (!WARN_ON_ONCE(old_ldt))
+                        free_ldt_pgtables(mm);
                 free_ldt_struct(new_ldt);
                 goto out_unlock;
         }