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userns: Remove the now unnecessary FS_USERNS_DEV_MOUNT flag 

Now that SB_I_NODEV controls the nodev behavior devpts can just clear
this flag during mount.  Simplifying the code and making it easier
to audit how the code works.  While still preserving the invariant
that s_iflags is only modified during mount.

Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2016-06-09 15:44:48 -05:00
parent 67690f937c
commit cc50a07a24
3 changed files with 3 additions and 4 deletions
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3
fs/devpts/inode.c
View File

@ -396,6 +396,7 @@ devpts_fill_super(struct super_block *s, void *data, int silent)
{
struct inode *inode;
s->s_iflags &= ~SB_I_NODEV;
s->s_blocksize = 1024;
s->s_blocksize_bits = 10;
s->s_magic = DEVPTS_SUPER_MAGIC;
@ -480,7 +481,7 @@ static struct file_system_type devpts_fs_type = {
.name = "devpts",
.mount = devpts_mount,
.kill_sb = devpts_kill_sb,
.fs_flags = FS_USERNS_MOUNT | FS_USERNS_DEV_MOUNT,
.fs_flags = FS_USERNS_MOUNT,
};
/*

3
fs/super.c
View File

@ -206,8 +206,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
init_waitqueue_head(&s->s_writers.wait_unfrozen);
s->s_bdi = &noop_backing_dev_info;
s->s_flags = flags;
if ((s->s_user_ns != &init_user_ns) &&
!(type->fs_flags & FS_USERNS_DEV_MOUNT))
if (s->s_user_ns != &init_user_ns)
s->s_iflags |= SB_I_NODEV;
INIT_HLIST_NODE(&s->s_instances);
INIT_HLIST_BL_HEAD(&s->s_anon);

1
include/linux/fs.h
View File

@ -2022,7 +2022,6 @@ struct file_system_type {
#define FS_BINARY_MOUNTDATA 2
#define FS_HAS_SUBTYPE 4
#define FS_USERNS_MOUNT 8 /* Can be mounted by userns root */
#define FS_USERNS_DEV_MOUNT 16 /* A userns mount does not imply MNT_NODEV */
#define FS_RENAME_DOES_D_MOVE 32768 /* FS will handle d_move() during rename() internally. */
struct dentry *(*mount) (struct file_system_type *, int,
const char *, void *);