linux-kernel - [PATCH v2 01/10] kvm: Restrict non-existing slot state transitions

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 10 Dec 2012 10:32:45 -0700
From:	Alex Williamson <alex.williamson@...hat.com>
To:	mtosatti@...hat.com, gleb@...hat.com
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: [PATCH v2 01/10] kvm: Restrict non-existing slot state transitions

The API documentation states:

	When changing an existing slot, it may be moved in the guest
	physical memory space, or its flags may be modified.

An "existing slot" requires a non-zero npages (memory_size).  The only
transition we should therefore allow for a non-existing slot should be
to create the slot, which includes setting a non-zero memory_size.  We
currently allow calls to modify non-existing slots, which is pointless,
confusing, and possibly wrong.

With this we know that the invalidation path of __kvm_set_memory_region
is always for a delete or move and never for adding a zero size slot.

Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
---
 virt/kvm/kvm_main.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6e8fa7e..e426704 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -753,10 +753,15 @@ int __kvm_set_memory_region(struct kvm *kvm,
 	new.npages = npages;
 	new.flags = mem->flags;
 
-	/* Disallow changing a memory slot's size. */
+	/*
+	 * Disallow changing a memory slot's size or changing anything about
+	 * zero sized slots that doesn't involve making them non-zero.
+	 */
 	r = -EINVAL;
 	if (npages && old.npages && npages != old.npages)
 		goto out_free;
+	if (!npages && !old.npages)
+		goto out_free;
 
 	/* Check for overlaps */
 	r = -EEXIST;
@@ -775,7 +780,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
 	r = -ENOMEM;
 
 	/* Allocate if a slot is being created */
-	if (npages && !old.npages) {
+	if (!old.npages) {
 		new.user_alloc = user_alloc;
 		new.userspace_addr = mem->userspace_addr;
 

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/