| 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
| ||
|
Message-ID: <d1940d466fc69472c8b6dda95df2e0522b2d8744.1726009989.git.ackerleytng@google.com>
Date: Tue, 10 Sep 2024 23:43:44 +0000
From: Ackerley Tng <ackerleytng@...gle.com>
To: tabba@...gle.com, quic_eberman@...cinc.com, roypat@...zon.co.uk,
jgg@...dia.com, peterx@...hat.com, david@...hat.com, rientjes@...gle.com,
fvdl@...gle.com, jthoughton@...gle.com, seanjc@...gle.com,
pbonzini@...hat.com, zhiquan1.li@...el.com, fan.du@...el.com,
jun.miao@...el.com, isaku.yamahata@...el.com, muchun.song@...ux.dev,
mike.kravetz@...cle.com
Cc: erdemaktas@...gle.com, vannapurve@...gle.com, ackerleytng@...gle.com,
qperret@...gle.com, jhubbard@...dia.com, willy@...radead.org,
shuah@...nel.org, brauner@...nel.org, bfoster@...hat.com,
kent.overstreet@...ux.dev, pvorel@...e.cz, rppt@...nel.org,
richard.weiyang@...il.com, anup@...infault.org, haibo1.xu@...el.com,
ajones@...tanamicro.com, vkuznets@...hat.com, maciej.wieczor-retman@...el.com,
pgonda@...gle.com, oliver.upton@...ux.dev, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
linux-fsdevel@...ck.org
Subject: [RFC PATCH 13/39] KVM: guest_memfd: Make guest mem use guest mem
inodes instead of anonymous inodes
Using guest mem inodes allows us to store metadata for the backing
memory on the inode. Metadata will be added in a later patch to
support HugeTLB pages.
Metadata about backing memory should not be stored on the file, since
the file represents a guest_memfd's binding with a struct kvm, and
metadata about backing memory is not unique to a specific binding and
struct kvm.
Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
---
include/uapi/linux/magic.h | 1 +
virt/kvm/guest_memfd.c | 119 ++++++++++++++++++++++++++++++-------
2 files changed, 100 insertions(+), 20 deletions(-)
diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
index bb575f3ab45e..169dba2a6920 100644
--- a/include/uapi/linux/magic.h
+++ b/include/uapi/linux/magic.h
@@ -103,5 +103,6 @@
#define DEVMEM_MAGIC 0x454d444d /* "DMEM" */
#define SECRETMEM_MAGIC 0x5345434d /* "SECM" */
#define PID_FS_MAGIC 0x50494446 /* "PIDF" */
+#define GUEST_MEMORY_MAGIC 0x474d454d /* "GMEM" */
#endif /* __LINUX_MAGIC_H__ */
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 8f079a61a56d..5d7fd1f708a6 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -1,12 +1,17 @@
// SPDX-License-Identifier: GPL-2.0
+#include <linux/fs.h>
+#include <linux/mount.h>
#include <linux/backing-dev.h>
#include <linux/falloc.h>
#include <linux/kvm_host.h>
+#include <linux/pseudo_fs.h>
#include <linux/pagemap.h>
#include <linux/anon_inodes.h>
#include "kvm_mm.h"
+static struct vfsmount *kvm_gmem_mnt;
+
struct kvm_gmem {
struct kvm *kvm;
struct xarray bindings;
@@ -302,6 +307,38 @@ static inline struct file *kvm_gmem_get_file(struct kvm_memory_slot *slot)
return get_file_active(&slot->gmem.file);
}
+static const struct super_operations kvm_gmem_super_operations = {
+ .statfs = simple_statfs,
+};
+
+static int kvm_gmem_init_fs_context(struct fs_context *fc)
+{
+ struct pseudo_fs_context *ctx;
+
+ if (!init_pseudo(fc, GUEST_MEMORY_MAGIC))
+ return -ENOMEM;
+
+ ctx = fc->fs_private;
+ ctx->ops = &kvm_gmem_super_operations;
+
+ return 0;
+}
+
+static struct file_system_type kvm_gmem_fs = {
+ .name = "kvm_guest_memory",
+ .init_fs_context = kvm_gmem_init_fs_context,
+ .kill_sb = kill_anon_super,
+};
+
+static void kvm_gmem_init_mount(void)
+{
+ kvm_gmem_mnt = kern_mount(&kvm_gmem_fs);
+ BUG_ON(IS_ERR(kvm_gmem_mnt));
+
+ /* For giggles. Userspace can never map this anyways. */
+ kvm_gmem_mnt->mnt_flags |= MNT_NOEXEC;
+}
+
static struct file_operations kvm_gmem_fops = {
.open = generic_file_open,
.release = kvm_gmem_release,
@@ -311,6 +348,8 @@ static struct file_operations kvm_gmem_fops = {
void kvm_gmem_init(struct module *module)
{
kvm_gmem_fops.owner = module;
+
+ kvm_gmem_init_mount();
}
static int kvm_gmem_migrate_folio(struct address_space *mapping,
@@ -392,11 +431,67 @@ static const struct inode_operations kvm_gmem_iops = {
.setattr = kvm_gmem_setattr,
};
+static struct inode *kvm_gmem_inode_make_secure_inode(const char *name,
+ loff_t size, u64 flags)
+{
+ const struct qstr qname = QSTR_INIT(name, strlen(name));
+ struct inode *inode;
+ int err;
+
+ inode = alloc_anon_inode(kvm_gmem_mnt->mnt_sb);
+ if (IS_ERR(inode))
+ return inode;
+
+ err = security_inode_init_security_anon(inode, &qname, NULL);
+ if (err) {
+ iput(inode);
+ return ERR_PTR(err);
+ }
+
+ inode->i_private = (void *)(unsigned long)flags;
+ inode->i_op = &kvm_gmem_iops;
+ inode->i_mapping->a_ops = &kvm_gmem_aops;
+ inode->i_mode |= S_IFREG;
+ inode->i_size = size;
+ mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
+ mapping_set_inaccessible(inode->i_mapping);
+ /* Unmovable mappings are supposed to be marked unevictable as well. */
+ WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping));
+
+ return inode;
+}
+
+static struct file *kvm_gmem_inode_create_getfile(void *priv, loff_t size,
+ u64 flags)
+{
+ static const char *name = "[kvm-gmem]";
+ struct inode *inode;
+ struct file *file;
+
+ if (kvm_gmem_fops.owner && !try_module_get(kvm_gmem_fops.owner))
+ return ERR_PTR(-ENOENT);
+
+ inode = kvm_gmem_inode_make_secure_inode(name, size, flags);
+ if (IS_ERR(inode))
+ return ERR_CAST(inode);
+
+ file = alloc_file_pseudo(inode, kvm_gmem_mnt, name, O_RDWR,
+ &kvm_gmem_fops);
+ if (IS_ERR(file)) {
+ iput(inode);
+ return file;
+ }
+
+ file->f_mapping = inode->i_mapping;
+ file->f_flags |= O_LARGEFILE;
+ file->private_data = priv;
+
+ return file;
+}
+
static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags)
{
- const char *anon_name = "[kvm-gmem]";
struct kvm_gmem *gmem;
- struct inode *inode;
struct file *file;
int fd, err;
@@ -410,32 +505,16 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags)
goto err_fd;
}
- file = anon_inode_create_getfile(anon_name, &kvm_gmem_fops, gmem,
- O_RDWR, NULL);
+ file = kvm_gmem_inode_create_getfile(gmem, size, flags);
if (IS_ERR(file)) {
err = PTR_ERR(file);
goto err_gmem;
}
- file->f_flags |= O_LARGEFILE;
-
- inode = file->f_inode;
- WARN_ON(file->f_mapping != inode->i_mapping);
-
- inode->i_private = (void *)(unsigned long)flags;
- inode->i_op = &kvm_gmem_iops;
- inode->i_mapping->a_ops = &kvm_gmem_aops;
- inode->i_mode |= S_IFREG;
- inode->i_size = size;
- mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
- mapping_set_inaccessible(inode->i_mapping);
- /* Unmovable mappings are supposed to be marked unevictable as well. */
- WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping));
-
kvm_get_kvm(kvm);
gmem->kvm = kvm;
xa_init(&gmem->bindings);
- list_add(&gmem->entry, &inode->i_mapping->i_private_list);
+ list_add(&gmem->entry, &file_inode(file)->i_mapping->i_private_list);
fd_install(fd, file);
return fd;
--
2.46.0.598.g6f2099f65c-goog
Powered by blists - more mailing lists