linux-kernel - [RFC PATCH 8/8] kvm: gmem: Allow restricted userspace mappings

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]

Message-ID: <20240709132041.3625501-9-roypat@amazon.co.uk>
Date: Tue, 9 Jul 2024 14:20:36 +0100
From: Patrick Roy <roypat@...zon.co.uk>
To: <seanjc@...gle.com>, <pbonzini@...hat.com>, <akpm@...ux-foundation.org>,
	<dwmw@...zon.co.uk>, <rppt@...nel.org>, <david@...hat.com>
CC: Patrick Roy <roypat@...zon.co.uk>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>,
	<x86@...nel.org>, <hpa@...or.com>, <willy@...radead.org>, <graf@...zon.com>,
	<derekmn@...zon.com>, <kalyazin@...zon.com>, <kvm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>, <dmatlack@...gle.com>,
	<tabba@...gle.com>, <chao.p.peng@...ux.intel.com>, <xmarcalx@...zon.co.uk>
Subject: [RFC PATCH 8/8] kvm: gmem: Allow restricted userspace mappings

Allow mapping guest_memfd into userspace. Since AS_INACCESSIBLE is set
on the underlying address_space struct, no GUP of guest_memfd will be
possible.

Signed-off-by: Patrick Roy <roypat@...zon.co.uk>
---
 virt/kvm/guest_memfd.c | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index dc9b0c2d0b0e..101ec2b248bf 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -319,7 +319,37 @@ static inline struct file *kvm_gmem_get_file(struct kvm_memory_slot *slot)
 	return get_file_active(&slot->gmem.file);
 }
 
+static vm_fault_t kvm_gmem_fault(struct vm_fault *vmf)
+{
+	struct folio *folio;
+
+	folio = kvm_gmem_get_folio(file_inode(vmf->vma->vm_file), vmf->pgoff, true);
+
+	if (!folio)
+		return VM_FAULT_SIGBUS;
+
+	vmf->page = folio_file_page(folio, vmf->pgoff);
+
+	return VM_FAULT_LOCKED;
+}
+
+static const struct vm_operations_struct kvm_gmem_vm_ops = {
+	.fault = kvm_gmem_fault
+};
+
+static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
+		return -EINVAL;
+
+	vm_flags_set(vma, VM_DONTDUMP);
+	vma->vm_ops = &kvm_gmem_vm_ops;
+
+	return 0;
+}
+
 static struct file_operations kvm_gmem_fops = {
+	.mmap           = kvm_gmem_mmap,
 	.open		= generic_file_open,
 	.release	= kvm_gmem_release,
 	.fallocate	= kvm_gmem_fallocate,
@@ -594,7 +624,6 @@ static int __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
 		return -EFAULT;
 	}
 
-	gmem = file->private_data;
 	if (xa_load(&gmem->bindings, index) != slot) {
 		WARN_ON_ONCE(xa_load(&gmem->bindings, index));
 		return -EIO;
-- 
2.45.2