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linux-next/fs/efivarfs/file.c
Christian Brauner 21cb47be6f
inode: make init and permission helpers idmapped mount aware
The inode_owner_or_capable() helper determines whether the caller is the
owner of the inode or is capable with respect to that inode. Allow it to
handle idmapped mounts. If the inode is accessed through an idmapped
mount it according to the mount's user namespace. Afterwards the checks
are identical to non-idmapped mounts. If the initial user namespace is
passed nothing changes so non-idmapped mounts will see identical
behavior as before.

Similarly, allow the inode_init_owner() helper to handle idmapped
mounts. It initializes a new inode on idmapped mounts by mapping the
fsuid and fsgid of the caller from the mount's user namespace. If the
initial user namespace is passed nothing changes so non-idmapped mounts
will see identical behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-7-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:16 +01:00

192 lines
4.0 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2012 Red Hat, Inc.
* Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
*/
#include <linux/efi.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/mount.h>
#include "internal.h"
static ssize_t efivarfs_file_write(struct file *file,
const char __user *userbuf, size_t count, loff_t *ppos)
{
struct efivar_entry *var = file->private_data;
void *data;
u32 attributes;
struct inode *inode = file->f_mapping->host;
unsigned long datasize = count - sizeof(attributes);
ssize_t bytes;
bool set = false;
if (count < sizeof(attributes))
return -EINVAL;
if (copy_from_user(&attributes, userbuf, sizeof(attributes)))
return -EFAULT;
if (attributes & ~(EFI_VARIABLE_MASK))
return -EINVAL;
data = memdup_user(userbuf + sizeof(attributes), datasize);
if (IS_ERR(data))
return PTR_ERR(data);
bytes = efivar_entry_set_get_size(var, attributes, &datasize,
data, &set);
if (!set && bytes) {
if (bytes == -ENOENT)
bytes = -EIO;
goto out;
}
if (bytes == -ENOENT) {
drop_nlink(inode);
d_delete(file->f_path.dentry);
dput(file->f_path.dentry);
} else {
inode_lock(inode);
i_size_write(inode, datasize + sizeof(attributes));
inode->i_mtime = current_time(inode);
inode_unlock(inode);
}
bytes = count;
out:
kfree(data);
return bytes;
}
static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
size_t count, loff_t *ppos)
{
struct efivar_entry *var = file->private_data;
unsigned long datasize = 0;
u32 attributes;
void *data;
ssize_t size = 0;
int err;
while (!__ratelimit(&file->f_cred->user->ratelimit))
msleep(50);
err = efivar_entry_size(var, &datasize);
/*
* efivarfs represents uncommitted variables with
* zero-length files. Reading them should return EOF.
*/
if (err == -ENOENT)
return 0;
else if (err)
return err;
data = kmalloc(datasize + sizeof(attributes), GFP_KERNEL);
if (!data)
return -ENOMEM;
size = efivar_entry_get(var, &attributes, &datasize,
data + sizeof(attributes));
if (size)
goto out_free;
memcpy(data, &attributes, sizeof(attributes));
size = simple_read_from_buffer(userbuf, count, ppos,
data, datasize + sizeof(attributes));
out_free:
kfree(data);
return size;
}
static inline unsigned int efivarfs_getflags(struct inode *inode)
{
unsigned int i_flags;
unsigned int flags = 0;
i_flags = inode->i_flags;
if (i_flags & S_IMMUTABLE)
flags |= FS_IMMUTABLE_FL;
return flags;
}
static int
efivarfs_ioc_getxflags(struct file *file, void __user *arg)
{
struct inode *inode = file->f_mapping->host;
unsigned int flags = efivarfs_getflags(inode);
if (copy_to_user(arg, &flags, sizeof(flags)))
return -EFAULT;
return 0;
}
static int
efivarfs_ioc_setxflags(struct file *file, void __user *arg)
{
struct inode *inode = file->f_mapping->host;
unsigned int flags;
unsigned int i_flags = 0;
unsigned int oldflags = efivarfs_getflags(inode);
int error;
if (!inode_owner_or_capable(&init_user_ns, inode))
return -EACCES;
if (copy_from_user(&flags, arg, sizeof(flags)))
return -EFAULT;
if (flags & ~FS_IMMUTABLE_FL)
return -EOPNOTSUPP;
if (flags & FS_IMMUTABLE_FL)
i_flags |= S_IMMUTABLE;
error = mnt_want_write_file(file);
if (error)
return error;
inode_lock(inode);
error = vfs_ioc_setflags_prepare(inode, oldflags, flags);
if (error)
goto out;
inode_set_flags(inode, i_flags, S_IMMUTABLE);
out:
inode_unlock(inode);
mnt_drop_write_file(file);
return error;
}
static long
efivarfs_file_ioctl(struct file *file, unsigned int cmd, unsigned long p)
{
void __user *arg = (void __user *)p;
switch (cmd) {
case FS_IOC_GETFLAGS:
return efivarfs_ioc_getxflags(file, arg);
case FS_IOC_SETFLAGS:
return efivarfs_ioc_setxflags(file, arg);
}
return -ENOTTY;
}
const struct file_operations efivarfs_file_operations = {
.open = simple_open,
.read = efivarfs_file_read,
.write = efivarfs_file_write,
.llseek = no_llseek,
.unlocked_ioctl = efivarfs_file_ioctl,
};