From aea270e3f7c0db696c88a0e94b1ece7abd339c84 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Fri, 21 Feb 2020 17:09:28 +0100 Subject: [PATCH] x86/p2m: fix PoD accounting in guest_physmap_add_entry() The initial observation was that the mfn_valid() check comes too late: Neither mfn_add() nor mfn_to_page() (let alone de-referencing the result of the latter) are valid for MFNs failing this check. Move it up and - noticing that there's no caller doing so - also add an assertion that this should never produce "false" here. In turn this would have meant that the "else" to that if() could now go away, which didn't seem right at all. And indeed, considering callers like memory_exchange() or various grant table functions, the PoD accounting should have been outside of that if() from the very beginning. Signed-off-by: Jan Beulich Acked-by: Andrew Cooper --- xen/arch/x86/mm/p2m.c | 32 ++++++++++++-------------------- 1 file changed, 12 insertions(+), 20 deletions(-) diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c index 263e6b4db8..3457877bfe 100644 --- a/xen/arch/x86/mm/p2m.c +++ b/xen/arch/x86/mm/p2m.c @@ -876,6 +876,12 @@ guest_physmap_add_entry(struct domain *d, gfn_t gfn, mfn_t mfn, if ( p2m_is_foreign(t) ) return -EINVAL; + if ( !mfn_valid(mfn) ) + { + ASSERT_UNREACHABLE(); + return -EINVAL; + } + p2m_lock(p2m); P2M_DEBUG("adding gfn=%#lx mfn=%#lx\n", gfn_x(gfn), mfn_x(mfn)); @@ -976,12 +982,13 @@ guest_physmap_add_entry(struct domain *d, gfn_t gfn, mfn_t mfn, } /* Now, actually do the two-way mapping */ - if ( mfn_valid(mfn) ) + rc = p2m_set_entry(p2m, gfn, mfn, page_order, t, p2m->default_access); + if ( rc == 0 ) { - rc = p2m_set_entry(p2m, gfn, mfn, page_order, t, - p2m->default_access); - if ( rc ) - goto out; /* Failed to update p2m, bail without updating m2p. */ + pod_lock(p2m); + p2m->pod.entry_count -= pod_count; + BUG_ON(p2m->pod.entry_count < 0); + pod_unlock(p2m); if ( !p2m_is_grant(t) ) { @@ -990,22 +997,7 @@ guest_physmap_add_entry(struct domain *d, gfn_t gfn, mfn_t mfn, gfn_x(gfn_add(gfn, i))); } } - else - { - gdprintk(XENLOG_WARNING, "Adding bad mfn to p2m map (%#lx -> %#lx)\n", - gfn_x(gfn), mfn_x(mfn)); - rc = p2m_set_entry(p2m, gfn, INVALID_MFN, page_order, - p2m_invalid, p2m->default_access); - if ( rc == 0 ) - { - pod_lock(p2m); - p2m->pod.entry_count -= pod_count; - BUG_ON(p2m->pod.entry_count < 0); - pod_unlock(p2m); - } - } -out: p2m_unlock(p2m); return rc; -- 2.39.5