From: Rusty Russell Date: Tue, 31 Mar 2009 01:55:04 +0000 (+0000) Subject: lguest: fix spurious BUG_ON() on invalid guest stack. X-Git-Tag: v2.6.29.1~7 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=4d25e3d0370354092b04aa338df14fb0b4c63331;p=karo-tx-linux.git lguest: fix spurious BUG_ON() on invalid guest stack. upstream commit: 6afbdd059c27330eccbd85943354f94c2b83a7fe 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 Signed-off-by: Chris Wright --- diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c index 576a8318221c..82ff484bd8c8 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))