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

Greg Kroah-Hartman
2018-01-01T14:48:25Z

From: Thomas Gleixner <tglx@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 <luto@amacapital.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@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;
}