[PATCH v6 38/40] ext4: support idmapped mounts
Christian Brauner
christian.brauner at ubuntu.com
Thu Jan 21 13:19:57 UTC 2021
Enable idmapped mounts for ext4. All dedicated helpers we need for this
exist. So this basically just means we're passing down the
user_namespace argument from the VFS methods to the relevant helpers.
Let's create simple example where we idmap an ext4 filesystem:
root at f2-vm:~# truncate -s 5G ext4.img
root at f2-vm:~# mkfs.ext4 ./ext4.img
mke2fs 1.45.5 (07-Jan-2020)
Discarding device blocks: done
Creating filesystem with 1310720 4k blocks and 327680 inodes
Filesystem UUID: 3fd91794-c6ca-4b0f-9964-289a000919cf
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736
Allocating group tables: done
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done
root at f2-vm:~# losetup -f --show ./ext4.img
/dev/loop0
root at f2-vm:~# mount /dev/loop0 /mnt
root at f2-vm:~# ls -al /mnt/
total 24
drwxr-xr-x 3 root root 4096 Oct 28 13:34 .
drwxr-xr-x 30 root root 4096 Oct 28 13:22 ..
drwx------ 2 root root 16384 Oct 28 13:34 lost+found
# Let's create an idmapped mount at /idmapped1 where we map uid and gid
# 0 to uid and gid 1000
root at f2-vm:/# ./mount-idmapped --map-mount b:0:1000:1 /mnt/ /idmapped1/
root at f2-vm:/# ls -al /idmapped1/
total 24
drwxr-xr-x 3 ubuntu ubuntu 4096 Oct 28 13:34 .
drwxr-xr-x 30 root root 4096 Oct 28 13:22 ..
drwx------ 2 ubuntu ubuntu 16384 Oct 28 13:34 lost+found
# Let's create an idmapped mount at /idmapped2 where we map uid and gid
# 0 to uid and gid 2000
root at f2-vm:/# ./mount-idmapped --map-mount b:0:2000:1 /mnt/ /idmapped2/
root at f2-vm:/# ls -al /idmapped2/
total 24
drwxr-xr-x 3 2000 2000 4096 Oct 28 13:34 .
drwxr-xr-x 31 root root 4096 Oct 28 13:39 ..
drwx------ 2 2000 2000 16384 Oct 28 13:34 lost+found
Let's create another example where we idmap the rootfs filesystem
without a mapping for uid 0 and gid 0:
# Create an idmapped mount of for a full POSIX range of rootfs under
# /mnt but without a mapping for uid 0 to reduce attack surface
root at f2-vm:/# ./mount-idmapped --map-mount b:1:1:65536 / /mnt/
# Since we don't have a mapping for uid and gid 0 all files owned by
# uid and gid 0 should show up as uid and gid 65534:
root at f2-vm:/# ls -al /mnt/
total 664
drwxr-xr-x 31 nobody nogroup 4096 Oct 28 13:39 .
drwxr-xr-x 31 root root 4096 Oct 28 13:39 ..
lrwxrwxrwx 1 nobody nogroup 7 Aug 25 07:44 bin -> usr/bin
drwxr-xr-x 4 nobody nogroup 4096 Oct 28 13:17 boot
drwxr-xr-x 2 nobody nogroup 4096 Aug 25 07:48 dev
drwxr-xr-x 81 nobody nogroup 4096 Oct 28 04:00 etc
drwxr-xr-x 4 nobody nogroup 4096 Oct 28 04:00 home
lrwxrwxrwx 1 nobody nogroup 7 Aug 25 07:44 lib -> usr/lib
lrwxrwxrwx 1 nobody nogroup 9 Aug 25 07:44 lib32 -> usr/lib32
lrwxrwxrwx 1 nobody nogroup 9 Aug 25 07:44 lib64 -> usr/lib64
lrwxrwxrwx 1 nobody nogroup 10 Aug 25 07:44 libx32 -> usr/libx32
drwx------ 2 nobody nogroup 16384 Aug 25 07:47 lost+found
drwxr-xr-x 2 nobody nogroup 4096 Aug 25 07:44 media
drwxr-xr-x 31 nobody nogroup 4096 Oct 28 13:39 mnt
drwxr-xr-x 2 nobody nogroup 4096 Aug 25 07:44 opt
drwxr-xr-x 2 nobody nogroup 4096 Apr 15 2020 proc
drwx--x--x 6 nobody nogroup 4096 Oct 28 13:34 root
drwxr-xr-x 2 nobody nogroup 4096 Aug 25 07:46 run
lrwxrwxrwx 1 nobody nogroup 8 Aug 25 07:44 sbin -> usr/sbin
drwxr-xr-x 2 nobody nogroup 4096 Aug 25 07:44 srv
drwxr-xr-x 2 nobody nogroup 4096 Apr 15 2020 sys
drwxrwxrwt 10 nobody nogroup 4096 Oct 28 13:19 tmp
drwxr-xr-x 14 nobody nogroup 4096 Oct 20 13:00 usr
drwxr-xr-x 12 nobody nogroup 4096 Aug 25 07:45 var
# Since we do have a mapping for uid and gid 1000 all files owned by
# uid and gid 1000 should simply show up as uid and gid 1000:
root at f2-vm:/# ls -al /mnt/home/ubuntu/
total 40
drwxr-xr-x 3 ubuntu ubuntu 4096 Oct 28 00:43 .
drwxr-xr-x 4 nobody nogroup 4096 Oct 28 04:00 ..
-rw------- 1 ubuntu ubuntu 2936 Oct 28 12:26 .bash_history
-rw-r--r-- 1 ubuntu ubuntu 220 Feb 25 2020 .bash_logout
-rw-r--r-- 1 ubuntu ubuntu 3771 Feb 25 2020 .bashrc
-rw-r--r-- 1 ubuntu ubuntu 807 Feb 25 2020 .profile
-rw-r--r-- 1 ubuntu ubuntu 0 Oct 16 16:11 .sudo_as_admin_successful
-rw------- 1 ubuntu ubuntu 1144 Oct 28 00:43 .viminfo
Link: https://lore.kernel.org/r/20210112220124.837960-37-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch at lst.de>
Cc: David Howells <dhowells at redhat.com>
Cc: Al Viro <viro at zeniv.linux.org.uk>
Cc: linux-ext4 at vger.kernel.org
Cc: linux-fsdevel at vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
/* v2 */
unchanged
/* v3 */
unchanged
/* v4 */
- Mauricio Vásquez Bernal <mauricio at kinvolk.io>:
- Fix spelling mistake in ext4's new idmapped mount config option.
- Christoph Hellwig <hch at lst.de>:
- Drop the config option. If ever want an administrator to disable this
feature we can simply introduce a sysctl.
- Serge Hallyn <serge at hallyn.com>:
- Use "mnt_userns" to refer to a vfsmount's userns everywhere to make
terminology consistent.
/* v5 */
base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837
- Christoph Hellwig <hch at lst.de>:
- Use new file_mnt_user_ns() helper.
- Christian Brauner <christian.brauner at ubuntu.com>:
- Improve commit message.
/* v6 */
unchanged
base-commit: 19c329f6808995b142b3966301f217c831e7cf31
---
fs/ext4/acl.c | 3 +--
fs/ext4/ext4.h | 13 +++++++------
fs/ext4/ialloc.c | 7 ++++---
fs/ext4/inode.c | 11 ++++++-----
fs/ext4/ioctl.c | 19 +++++++++++--------
fs/ext4/namei.c | 30 ++++++++++++++++--------------
fs/ext4/super.c | 2 +-
7 files changed, 46 insertions(+), 39 deletions(-)
diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
index 059434e0f36c..c5eaffccecc3 100644
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -246,8 +246,7 @@ ext4_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
ext4_fc_start_update(inode);
if ((type == ACL_TYPE_ACCESS) && acl) {
- error = posix_acl_update_mode(&init_user_ns, inode, &mode,
- &acl);
+ error = posix_acl_update_mode(mnt_userns, inode, &mode, &acl);
if (error)
goto out_stop;
if (mode != inode->i_mode)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 3c750f5e8ebd..644fd69185d3 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2755,18 +2755,19 @@ extern int ext4fs_dirhash(const struct inode *dir, const char *name, int len,
/* ialloc.c */
extern int ext4_mark_inode_used(struct super_block *sb, int ino);
-extern struct inode *__ext4_new_inode(handle_t *, struct inode *, umode_t,
+extern struct inode *__ext4_new_inode(struct user_namespace *, handle_t *,
+ struct inode *, umode_t,
const struct qstr *qstr, __u32 goal,
uid_t *owner, __u32 i_flags,
int handle_type, unsigned int line_no,
int nblocks);
-#define ext4_new_inode(handle, dir, mode, qstr, goal, owner, i_flags) \
- __ext4_new_inode((handle), (dir), (mode), (qstr), (goal), (owner), \
- i_flags, 0, 0, 0)
-#define ext4_new_inode_start_handle(dir, mode, qstr, goal, owner, \
+#define ext4_new_inode(handle, dir, mode, qstr, goal, owner, i_flags) \
+ __ext4_new_inode(&init_user_ns, (handle), (dir), (mode), (qstr), \
+ (goal), (owner), i_flags, 0, 0, 0)
+#define ext4_new_inode_start_handle(mnt_userns, dir, mode, qstr, goal, owner, \
type, nblocks) \
- __ext4_new_inode(NULL, (dir), (mode), (qstr), (goal), (owner), \
+ __ext4_new_inode((mnt_userns), NULL, (dir), (mode), (qstr), (goal), (owner), \
0, (type), __LINE__, (nblocks))
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 00c1ec6eee16..bf9028950a51 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -919,7 +919,8 @@ static int ext4_xattr_credits_for_new_inode(struct inode *dir, mode_t mode,
* For other inodes, search forward from the parent directory's block
* group to find a free inode.
*/
-struct inode *__ext4_new_inode(handle_t *handle, struct inode *dir,
+struct inode *__ext4_new_inode(struct user_namespace *mnt_userns,
+ handle_t *handle, struct inode *dir,
umode_t mode, const struct qstr *qstr,
__u32 goal, uid_t *owner, __u32 i_flags,
int handle_type, unsigned int line_no,
@@ -969,10 +970,10 @@ struct inode *__ext4_new_inode(handle_t *handle, struct inode *dir,
i_gid_write(inode, owner[1]);
} else if (test_opt(sb, GRPID)) {
inode->i_mode = mode;
- inode->i_uid = current_fsuid();
+ inode->i_uid = fsuid_into_mnt(mnt_userns);
inode->i_gid = dir->i_gid;
} else
- inode_init_owner(&init_user_ns, inode, dir, mode);
+ inode_init_owner(mnt_userns, inode, dir, mode);
if (ext4_has_feature_project(sb) &&
ext4_test_inode_flag(dir, EXT4_INODE_PROJINHERIT))
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index ce45535336fa..8fbf85b3547e 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -20,6 +20,7 @@
*/
#include <linux/fs.h>
+#include <linux/mount.h>
#include <linux/time.h>
#include <linux/highuid.h>
#include <linux/pagemap.h>
@@ -5338,7 +5339,7 @@ int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
ATTR_GID | ATTR_TIMES_SET))))
return -EPERM;
- error = setattr_prepare(&init_user_ns, dentry, attr);
+ error = setattr_prepare(mnt_userns, dentry, attr);
if (error)
return error;
@@ -5513,7 +5514,7 @@ int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
}
if (!error) {
- setattr_copy(&init_user_ns, inode, attr);
+ setattr_copy(mnt_userns, inode, attr);
mark_inode_dirty(inode);
}
@@ -5525,7 +5526,7 @@ int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
ext4_orphan_del(NULL, inode);
if (!error && (ia_valid & ATTR_MODE))
- rc = posix_acl_chmod(&init_user_ns, inode, inode->i_mode);
+ rc = posix_acl_chmod(mnt_userns, inode, inode->i_mode);
err_out:
if (error)
@@ -5572,7 +5573,7 @@ int ext4_getattr(struct user_namespace *mnt_userns, const struct path *path,
STATX_ATTR_NODUMP |
STATX_ATTR_VERITY);
- generic_fillattr(&init_user_ns, inode, stat);
+ generic_fillattr(mnt_userns, inode, stat);
return 0;
}
@@ -5583,7 +5584,7 @@ int ext4_file_getattr(struct user_namespace *mnt_userns,
struct inode *inode = d_inode(path->dentry);
u64 delalloc_blocks;
- ext4_getattr(&init_user_ns, path, stat, request_mask, query_flags);
+ ext4_getattr(mnt_userns, path, stat, request_mask, query_flags);
/*
* If there is inline data in the inode, the inode will normally not
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index ab80e2493fdc..56ad9c4b6350 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -107,10 +107,12 @@ void ext4_reset_inode_seed(struct inode *inode)
* important fields of the inodes.
*
* @sb: the super block of the filesystem
+ * @mnt_userns: user namespace of the mount the inode was found from
* @inode: the inode to swap with EXT4_BOOT_LOADER_INO
*
*/
static long swap_inode_boot_loader(struct super_block *sb,
+ struct user_namespace *mnt_userns,
struct inode *inode)
{
handle_t *handle;
@@ -139,7 +141,7 @@ static long swap_inode_boot_loader(struct super_block *sb,
}
if (IS_RDONLY(inode) || IS_APPEND(inode) || IS_IMMUTABLE(inode) ||
- !inode_owner_or_capable(&init_user_ns, inode) ||
+ !inode_owner_or_capable(mnt_userns, inode) ||
!capable(CAP_SYS_ADMIN)) {
err = -EPERM;
goto journal_err_out;
@@ -815,6 +817,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
struct inode *inode = file_inode(filp);
struct super_block *sb = inode->i_sb;
struct ext4_inode_info *ei = EXT4_I(inode);
+ struct user_namespace *mnt_userns = file_mnt_user_ns(filp);
unsigned int flags;
ext4_debug("cmd = %u, arg = %lu\n", cmd, arg);
@@ -830,7 +833,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
case FS_IOC_SETFLAGS: {
int err;
- if (!inode_owner_or_capable(&init_user_ns, inode))
+ if (!inode_owner_or_capable(mnt_userns, inode))
return -EACCES;
if (get_user(flags, (int __user *) arg))
@@ -872,7 +875,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
__u32 generation;
int err;
- if (!inode_owner_or_capable(&init_user_ns, inode))
+ if (!inode_owner_or_capable(mnt_userns, inode))
return -EPERM;
if (ext4_has_metadata_csum(inode->i_sb)) {
@@ -1011,7 +1014,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
case EXT4_IOC_MIGRATE:
{
int err;
- if (!inode_owner_or_capable(&init_user_ns, inode))
+ if (!inode_owner_or_capable(mnt_userns, inode))
return -EACCES;
err = mnt_want_write_file(filp);
@@ -1033,7 +1036,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
case EXT4_IOC_ALLOC_DA_BLKS:
{
int err;
- if (!inode_owner_or_capable(&init_user_ns, inode))
+ if (!inode_owner_or_capable(mnt_userns, inode))
return -EACCES;
err = mnt_want_write_file(filp);
@@ -1052,7 +1055,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
err = mnt_want_write_file(filp);
if (err)
return err;
- err = swap_inode_boot_loader(sb, inode);
+ err = swap_inode_boot_loader(sb, mnt_userns, inode);
mnt_drop_write_file(filp);
return err;
}
@@ -1218,7 +1221,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
case EXT4_IOC_CLEAR_ES_CACHE:
{
- if (!inode_owner_or_capable(&init_user_ns, inode))
+ if (!inode_owner_or_capable(mnt_userns, inode))
return -EACCES;
ext4_clear_inode_es(inode);
return 0;
@@ -1264,7 +1267,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
return -EFAULT;
/* Make sure caller has proper permission */
- if (!inode_owner_or_capable(&init_user_ns, inode))
+ if (!inode_owner_or_capable(mnt_userns, inode))
return -EACCES;
if (fa.fsx_xflags & ~EXT4_SUPPORTED_FS_XFLAGS)
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 13dff80aedcb..877c602ae063 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2610,8 +2610,8 @@ static int ext4_create(struct user_namespace *mnt_userns, struct inode *dir,
credits = (EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3);
retry:
- inode = ext4_new_inode_start_handle(dir, mode, &dentry->d_name, 0,
- NULL, EXT4_HT_DIR, credits);
+ inode = ext4_new_inode_start_handle(mnt_userns, dir, mode, &dentry->d_name,
+ 0, NULL, EXT4_HT_DIR, credits);
handle = ext4_journal_current_handle();
err = PTR_ERR(inode);
if (!IS_ERR(inode)) {
@@ -2645,8 +2645,8 @@ static int ext4_mknod(struct user_namespace *mnt_userns, struct inode *dir,
credits = (EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3);
retry:
- inode = ext4_new_inode_start_handle(dir, mode, &dentry->d_name, 0,
- NULL, EXT4_HT_DIR, credits);
+ inode = ext4_new_inode_start_handle(mnt_userns, dir, mode, &dentry->d_name,
+ 0, NULL, EXT4_HT_DIR, credits);
handle = ext4_journal_current_handle();
err = PTR_ERR(inode);
if (!IS_ERR(inode)) {
@@ -2677,7 +2677,7 @@ static int ext4_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
return err;
retry:
- inode = ext4_new_inode_start_handle(dir, mode,
+ inode = ext4_new_inode_start_handle(mnt_userns, dir, mode,
NULL, 0, NULL,
EXT4_HT_DIR,
EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb) +
@@ -2792,7 +2792,7 @@ static int ext4_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
credits = (EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3);
retry:
- inode = ext4_new_inode_start_handle(dir, S_IFDIR | mode,
+ inode = ext4_new_inode_start_handle(mnt_userns, dir, S_IFDIR | mode,
&dentry->d_name,
0, NULL, EXT4_HT_DIR, credits);
handle = ext4_journal_current_handle();
@@ -3335,7 +3335,7 @@ static int ext4_symlink(struct user_namespace *mnt_userns, struct inode *dir,
EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3;
}
- inode = ext4_new_inode_start_handle(dir, S_IFLNK|S_IRWXUGO,
+ inode = ext4_new_inode_start_handle(mnt_userns, dir, S_IFLNK|S_IRWXUGO,
&dentry->d_name, 0, NULL,
EXT4_HT_DIR, credits);
handle = ext4_journal_current_handle();
@@ -3664,7 +3664,8 @@ static void ext4_update_dir_count(handle_t *handle, struct ext4_renament *ent)
}
}
-static struct inode *ext4_whiteout_for_rename(struct ext4_renament *ent,
+static struct inode *ext4_whiteout_for_rename(struct user_namespace *mnt_userns,
+ struct ext4_renament *ent,
int credits, handle_t **h)
{
struct inode *wh;
@@ -3678,7 +3679,8 @@ static struct inode *ext4_whiteout_for_rename(struct ext4_renament *ent,
credits += (EXT4_MAXQUOTAS_TRANS_BLOCKS(ent->dir->i_sb) +
EXT4_XATTR_TRANS_BLOCKS + 4);
retry:
- wh = ext4_new_inode_start_handle(ent->dir, S_IFCHR | WHITEOUT_MODE,
+ wh = ext4_new_inode_start_handle(mnt_userns, ent->dir,
+ S_IFCHR | WHITEOUT_MODE,
&ent->dentry->d_name, 0, NULL,
EXT4_HT_DIR, credits);
@@ -3705,9 +3707,9 @@ static struct inode *ext4_whiteout_for_rename(struct ext4_renament *ent,
* while new_{dentry,inode) refers to the destination dentry/inode
* This comes from rename(const char *oldpath, const char *newpath)
*/
-static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
- struct inode *new_dir, struct dentry *new_dentry,
- unsigned int flags)
+static int ext4_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
+ struct dentry *old_dentry, struct inode *new_dir,
+ struct dentry *new_dentry, unsigned int flags)
{
handle_t *handle = NULL;
struct ext4_renament old = {
@@ -3791,7 +3793,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
goto end_rename;
}
} else {
- whiteout = ext4_whiteout_for_rename(&old, credits, &handle);
+ whiteout = ext4_whiteout_for_rename(mnt_userns, &old, credits, &handle);
if (IS_ERR(whiteout)) {
retval = PTR_ERR(whiteout);
whiteout = NULL;
@@ -4110,7 +4112,7 @@ static int ext4_rename2(struct user_namespace *mnt_userns,
new_dir, new_dentry);
}
- return ext4_rename(old_dir, old_dentry, new_dir, new_dentry, flags);
+ return ext4_rename(mnt_userns, old_dir, old_dentry, new_dir, new_dentry, flags);
}
/*
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 9a6f9875aa34..a77fbb79e813 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -6654,7 +6654,7 @@ static struct file_system_type ext4_fs_type = {
.name = "ext4",
.mount = ext4_mount,
.kill_sb = kill_block_super,
- .fs_flags = FS_REQUIRES_DEV,
+ .fs_flags = FS_REQUIRES_DEV | FS_ALLOW_IDMAP,
};
MODULE_ALIAS_FS("ext4");
--
2.30.0
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