[x86] kvm: Reload pit counters for all channels when restoring state (CVE-2015-7513)

3 files changed, 56 insertions, 0 deletions

diff --git a/debian/changelog b/debian/changelog
index bcb12a961a3c..031bdfee2b04 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -13,6 +13,8 @@ linux (4.3.3-3) UNRELEASED; urgency=medium
 
   [ Salvatore Bonaccorso ]
   * ovl: fix permission checking for setattr (CVE-2015-8660)
+  * [x86] kvm: Reload pit counters for all channels when restoring state
+    (CVE-2015-7513)
 
  -- Ben Hutchings <ben@decadent.org.uk>  Fri, 18 Dec 2015 20:19:24 +0000
 
diff --git a/debian/patches/bugfix/x86/KVM-x86-Reload-pit-counters-for-all-channels-when-re.patch b/debian/patches/bugfix/x86/KVM-x86-Reload-pit-counters-for-all-channels-when-re.patch
new file mode 100644
index 000000000000..9359d34e0e3b
--- /dev/null
+++ b/debian/patches/bugfix/x86/KVM-x86-Reload-pit-counters-for-all-channels-when-re.patch
@@ -0,0 +1,53 @@
+From: Andrew Honig <ahonig@google.com>
+Date: Wed, 18 Nov 2015 14:50:23 -0800
+Subject: KVM: x86: Reload pit counters for all channels when restoring state
+Origin: https://git.kernel.org/linus/0185604c2d82c560dab2f2933a18f797e74ab5a8
+
+Currently if userspace restores the pit counters with a count of 0
+on channels 1 or 2 and the guest attempts to read the count on those
+channels, then KVM will perform a mod of 0 and crash.  This will ensure
+that 0 values are converted to 65536 as per the spec.
+
+This is CVE-2015-7513.
+
+Signed-off-by: Andy Honig <ahonig@google.com>
+Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
+[carnil: Backport to 4.3.3: context]
+---
+ arch/x86/kvm/x86.c | 8 ++++++--
+ 1 file changed, 6 insertions(+), 2 deletions(-)
+
+--- a/arch/x86/kvm/x86.c
++++ b/arch/x86/kvm/x86.c
+@@ -3437,10 +3437,11 @@ static int kvm_vm_ioctl_get_pit(struct k
+ static int kvm_vm_ioctl_set_pit(struct kvm *kvm, struct kvm_pit_state *ps)
+ {
+ 	int r = 0;
+-
++	int i;
+ 	mutex_lock(&kvm->arch.vpit->pit_state.lock);
+ 	memcpy(&kvm->arch.vpit->pit_state, ps, sizeof(struct kvm_pit_state));
+-	kvm_pit_load_count(kvm, 0, ps->channels[0].count, 0);
++	for (i = 0; i < 3; i++)
++		kvm_pit_load_count(kvm, i, ps->channels[i].count, 0);
+ 	mutex_unlock(&kvm->arch.vpit->pit_state.lock);
+ 	return r;
+ }
+@@ -3461,6 +3462,7 @@ static int kvm_vm_ioctl_get_pit2(struct
+ static int kvm_vm_ioctl_set_pit2(struct kvm *kvm, struct kvm_pit_state2 *ps)
+ {
+ 	int r = 0, start = 0;
++	int i;
+ 	u32 prev_legacy, cur_legacy;
+ 	mutex_lock(&kvm->arch.vpit->pit_state.lock);
+ 	prev_legacy = kvm->arch.vpit->pit_state.flags & KVM_PIT_FLAGS_HPET_LEGACY;
+@@ -3470,7 +3472,8 @@ static int kvm_vm_ioctl_set_pit2(struct
+ 	memcpy(&kvm->arch.vpit->pit_state.channels, &ps->channels,
+ 	       sizeof(kvm->arch.vpit->pit_state.channels));
+ 	kvm->arch.vpit->pit_state.flags = ps->flags;
+-	kvm_pit_load_count(kvm, 0, kvm->arch.vpit->pit_state.channels[0].count, start);
++	for (i = 0; i < 3; i++)
++		kvm_pit_load_count(kvm, i, kvm->arch.vpit->pit_state.channels[i].count, start);
+ 	mutex_unlock(&kvm->arch.vpit->pit_state.lock);
+ 	return r;
+ }
diff --git a/debian/patches/series b/debian/patches/series
index 9cafb259e8da..94167d7a9a87 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -127,3 +127,4 @@ bugfix/all/xen-pciback-for-xen_pci_op_disable_msi-x-only-disabl.patch
 bugfix/all/xen-pciback-don-t-allow-msi-x-ops-if-pci_command_mem.patch
 bugfix/all/ptrace-being-capable-wrt-a-process-requires-mapped-uids-gids.patch
 bugfix/all/keys-fix-race-between-read-and-revoke.patch
+bugfix/x86/KVM-x86-Reload-pit-counters-for-all-channels-when-re.patch