Messages in this thread Patch in this message | | | From | Rusty Russell <> | Date | Fri, 27 Mar 2009 10:21:40 +1030 | Subject | [PATCH 1/5] lguest: fix spurious BUG_ON() on invalid guest stack. |
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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 <rusty@rustcorp.com.au> --- 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 --- a/drivers/lguest/page_tables.c +++ b/drivers/lguest/page_tables.c @@ -373,8 +373,10 @@ unsigned long guest_pa(struct lg_cpu *cp /* 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))
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