[PATCH 4.14 144/146] x86/ldt: Make LDT pgtable free conditional

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <t...@linutronix.de>

commit 7f414195b0c3612acd12b4611a5fe75995cf10c7 upstream.

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 <l...@amacapital.net>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 arch/x86/kernel/ldt.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/ldt.c
+++ b/arch/x86/kernel/ldt.c
@@ -426,7 +426,8 @@ static int write_ldt(void __user *ptr, u
                 * 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;
        }