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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>
Cc: stable@kernel.org
This commit is contained in:
Rusty Russell 2009-03-30 21:55:23 -06:00
parent c5f841f178
commit 6afbdd059c
1 changed files with 3 additions and 1 deletions
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4
drivers/lguest/page_tables.c
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@ -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))