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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen stable-4.15] x86/p2m: guard (in particular) identity mapping entries
commit 7850fe53a59f73fbb0a61c36141c6a6563e3eeca
Author: Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Aug 25 14:43:45 2021 +0200
Commit: Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Aug 25 14:43:45 2021 +0200
x86/p2m: guard (in particular) identity mapping entries
Such entries, created by set_identity_p2m_entry(), should only be
destroyed by clear_identity_p2m_entry(). However, similarly, entries
created by set_mmio_p2m_entry() should only be torn down by
clear_mmio_p2m_entry(), so the logic gets based upon p2m_mmio_direct as
the entry type (separation between "ordinary" and 1:1 mappings would
require a further indicator to tell apart the two).
As to the guest_remove_page() change, commit 48dfb297a20a ("x86/PVH:
allow guest_remove_page to remove p2m_mmio_direct pages"), which
introduced the call to clear_mmio_p2m_entry(), claimed this was done for
hwdom only without this actually having been the case. However, this
code shouldn't be there in the first place, as MMIO entries shouldn't be
dropped this way. Avoid triggering the warning again that 48dfb297a20a
silenced by an adjustment to xenmem_add_to_physmap_one() instead.
Note that guest_physmap_mark_populate_on_demand() gets tightened beyond
the immediate purpose of this change.
Note also that I didn't inspect code which isn't security supported,
e.g. sharing, paging, or altp2m.
This is CVE-2021-28694 / part of XSA-378.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Paul Durrant <paul@xxxxxxx>
master commit: 753cb68e653002e89fdcd1c80e52905fdbfb78cb
master date: 2021-08-25 14:17:32 +0200
---
xen/arch/x86/mm/p2m-pod.c | 12 ++++++------
xen/arch/x86/mm/p2m.c | 15 +++++++++------
xen/common/memory.c | 11 ++++++++++-
xen/include/asm-x86/p2m.h | 5 ++---
4 files changed, 27 insertions(+), 16 deletions(-)
diff --git a/xen/arch/x86/mm/p2m-pod.c b/xen/arch/x86/mm/p2m-pod.c
index ae153fa6e6..8abc57265c 100644
--- a/xen/arch/x86/mm/p2m-pod.c
+++ b/xen/arch/x86/mm/p2m-pod.c
@@ -1299,17 +1299,17 @@ guest_physmap_mark_populate_on_demand(struct domain *d,
unsigned long gfn_l,
p2m->get_entry(p2m, gfn_add(gfn, i), &ot, &a, 0, &cur_order, NULL);
n = 1UL << min(order, cur_order);
- if ( p2m_is_ram(ot) )
+ if ( ot == p2m_populate_on_demand )
+ {
+ /* Count how many PoD entries we'll be replacing if successful */
+ pod_count += n;
+ }
+ else if ( ot != p2m_invalid && ot != p2m_mmio_dm )
{
P2M_DEBUG("gfn_to_mfn returned type %d!\n", ot);
rc = -EBUSY;
goto out;
}
- else if ( ot == p2m_populate_on_demand )
- {
- /* Count how man PoD entries we'll be replacing if successful */
- pod_count += n;
- }
}
/* Now, actually do the two-way mapping */
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 59764c6073..4cbb177aa9 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -799,7 +799,8 @@ p2m_remove_page(struct p2m_domain *p2m, gfn_t gfn, mfn_t
mfn,
&cur_order, NULL);
if ( p2m_is_valid(t) &&
- (!mfn_valid(mfn) || !mfn_eq(mfn_add(mfn, i), mfn_return)) )
+ (!mfn_valid(mfn) || t == p2m_mmio_direct ||
+ !mfn_eq(mfn_add(mfn, i), mfn_return)) )
return -EILSEQ;
i += (1UL << cur_order) -
@@ -899,7 +900,7 @@ guest_physmap_add_entry(struct domain *d, gfn_t gfn, mfn_t
mfn,
if ( p2m_is_foreign(t) )
return -EINVAL;
- if ( !mfn_valid(mfn) )
+ if ( !mfn_valid(mfn) || t == p2m_mmio_direct )
{
ASSERT_UNREACHABLE();
return -EINVAL;
@@ -943,7 +944,7 @@ guest_physmap_add_entry(struct domain *d, gfn_t gfn, mfn_t
mfn,
}
if ( p2m_is_special(ot) )
{
- /* Don't permit unmapping grant/foreign this way. */
+ /* Don't permit unmapping grant/foreign/direct-MMIO this way. */
domain_crash(d);
p2m_unlock(p2m);
@@ -1399,8 +1400,8 @@ int set_identity_p2m_entry(struct domain *d, unsigned
long gfn_l,
* order+1 for caller to retry with order (guaranteed smaller than
* the order value passed in)
*/
-int clear_mmio_p2m_entry(struct domain *d, unsigned long gfn_l, mfn_t mfn,
- unsigned int order)
+static int clear_mmio_p2m_entry(struct domain *d, unsigned long gfn_l,
+ mfn_t mfn, unsigned int order)
{
int rc = -EINVAL;
gfn_t gfn = _gfn(gfn_l);
@@ -2731,7 +2732,9 @@ int xenmem_add_to_physmap_one(
/* Remove previously mapped page if it was present. */
prev_mfn = get_gfn(d, gfn_x(gpfn), &p2mt);
- if ( mfn_valid(prev_mfn) )
+ if ( p2mt == p2m_mmio_direct )
+ rc = -EPERM;
+ else if ( mfn_valid(prev_mfn) )
{
if ( is_special_page(mfn_to_page(prev_mfn)) )
/* Special pages are simply unhooked from this phys slot. */
diff --git a/xen/common/memory.c b/xen/common/memory.c
index 76b9f58478..297b98a562 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -330,7 +330,7 @@ int guest_remove_page(struct domain *d, unsigned long gmfn)
}
if ( p2mt == p2m_mmio_direct )
{
- rc = clear_mmio_p2m_entry(d, gmfn, mfn, PAGE_ORDER_4K);
+ rc = -EPERM;
goto out_put_gfn;
}
#else
@@ -1875,6 +1875,15 @@ int check_get_page_from_gfn(struct domain *d, gfn_t gfn,
bool readonly,
return -EAGAIN;
}
#endif
+#ifdef CONFIG_X86
+ if ( p2mt == p2m_mmio_direct )
+ {
+ if ( page )
+ put_page(page);
+
+ return -EPERM;
+ }
+#endif
if ( !page )
return -EINVAL;
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index 18c3c42e9d..422a8b228f 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -151,7 +151,8 @@ typedef unsigned int p2m_query_t;
/* Types established/cleaned up via special accessors. */
#define P2M_SPECIAL_TYPES (P2M_GRANT_TYPES | \
- p2m_to_mask(p2m_map_foreign))
+ p2m_to_mask(p2m_map_foreign) | \
+ p2m_to_mask(p2m_mmio_direct))
/* Valid types not necessarily associated with a (valid) MFN. */
#define P2M_INVALID_MFN_TYPES (P2M_POD_TYPES \
@@ -666,8 +667,6 @@ int p2m_is_logdirty_range(struct p2m_domain *, unsigned
long start,
/* Set mmio addresses in the p2m table (for pass-through) */
int set_mmio_p2m_entry(struct domain *d, gfn_t gfn, mfn_t mfn,
unsigned int order);
-int clear_mmio_p2m_entry(struct domain *d, unsigned long gfn, mfn_t mfn,
- unsigned int order);
/* Set identity addresses in the p2m table (for pass-through) */
int set_identity_p2m_entry(struct domain *d, unsigned long gfn,
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.15
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