From: Rusty Russell <rusty@rustcorp.com.au>
Date: Thu, 5 Sep 2013 08:15:39 +0000 (+0930)
Subject: lguest: fix BUG_ON() in invalid guest page table.
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=4623c28e222d82f87537ef66db61ebcfbd8306db;p=linux-beck.git

lguest: fix BUG_ON() in invalid guest page table.

If we discover the entry is invalid, we kill the guest, but we must
avoid calling gpte_addr() on the invalid pmd, otherwise:

	kernel BUG at drivers/lguest/page_tables.c:157!

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---

diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c
index a35d8d100165..bfb39bb56ef1 100644
--- a/drivers/lguest/page_tables.c
+++ b/drivers/lguest/page_tables.c
@@ -669,8 +669,10 @@ unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr)
 
 #ifdef CONFIG_X86_PAE
 	gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t);
-	if (!(pmd_flags(gpmd) & _PAGE_PRESENT))
+	if (!(pmd_flags(gpmd) & _PAGE_PRESENT)) {
 		kill_guest(cpu, "Bad address %#lx", vaddr);
+		return -1UL;
+	}
 	gpte = lgread(cpu, gpte_addr(cpu, gpmd, vaddr), pte_t);
 #else
 	gpte = lgread(cpu, gpte_addr(cpu, gpgd, vaddr), pte_t);