From 6afbdd059c27330eccbd85943354f94c2b83a7fe Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Mon, 30 Mar 2009 21:55:23 -0600 Subject: [PATCH] lguest: fix spurious BUG_ON() on invalid guest stack. Impact: fix crash on misbehaving guest gpte_addr() contains a BUG_ON(), insisting that the present flag is set. We need to return before we call it if that isn't the case. Signed-off-by: Rusty Russell Cc: stable@kernel.org --- drivers/lguest/page_tables.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c index 576a8318221..82ff484bd8c 100644 --- a/drivers/lguest/page_tables.c +++ b/drivers/lguest/page_tables.c @@ -373,8 +373,10 @@ unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr) /* First step: get the top-level Guest page table entry. */ gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t); /* Toplevel not present? We can't map it in. */ - if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) + if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) { kill_guest(cpu, "Bad address %#lx", vaddr); + return -1UL; + } gpte = lgread(cpu, gpte_addr(gpgd, vaddr), pte_t); if (!(pte_flags(gpte) & _PAGE_PRESENT)) -- 2.41.1