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fs: support getname_maybe_null() in move_mount()

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Allow move_mount() to work with NULL path arguments.

Link: https://lore.kernel.org/r/20250221-brauner-open_tree-v1-8-dbcfcb98c676@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2025-02-21 14:13:07 +01:00
parent 3f1724dd56
commit f9fde814de
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
2 changed files with 61 additions and 33 deletions
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93
fs/namespace.c
View File

@ -2465,6 +2465,7 @@ int count_mounts(struct mnt_namespace *ns, struct mount *mnt)
enum mnt_tree_flags_t {
MNT_TREE_MOVE = BIT(0),
MNT_TREE_BENEATH = BIT(1),
MNT_TREE_PROPAGATION = BIT(2),
};
/**
@ -3436,8 +3437,8 @@ static int can_move_mount_beneath(const struct path *from,
return 0;
}
static int do_move_mount(struct path *old_path, struct path *new_path,
bool beneath)
static int do_move_mount(struct path *old_path,
struct path *new_path, enum mnt_tree_flags_t flags)
{
struct mnt_namespace *ns;
struct mount *p;
@ -3445,8 +3446,7 @@ static int do_move_mount(struct path *old_path, struct path *new_path,
struct mount *parent;
struct mountpoint *mp, *old_mp;
int err;
bool attached;
enum mnt_tree_flags_t flags = 0;
bool attached, beneath = flags & MNT_TREE_BENEATH;
mp = do_lock_mount(new_path, beneath);
if (IS_ERR(mp))
@ -3547,7 +3547,7 @@ static int do_move_mount_old(struct path *path, const char *old_name)
if (err)
return err;
err = do_move_mount(&old_path, path, false);
err = do_move_mount(&old_path, path, 0);
path_put(&old_path);
return err;
}
@ -4388,6 +4388,21 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
return ret;
}
static inline int vfs_move_mount(struct path *from_path, struct path *to_path,
enum mnt_tree_flags_t mflags)
{
int ret;
ret = security_move_mount(from_path, to_path);
if (ret)
return ret;
if (mflags & MNT_TREE_PROPAGATION)
return do_set_group(from_path, to_path);
return do_move_mount(from_path, to_path, mflags);
}
/*
* Move a mount from one place to another. In combination with
* fsopen()/fsmount() this is used to install a new mount and in combination
@ -4401,8 +4416,12 @@ SYSCALL_DEFINE5(move_mount,
int, to_dfd, const char __user *, to_pathname,
unsigned int, flags)
{
struct path from_path, to_path;
unsigned int lflags;
struct path to_path __free(path_put) = {};
struct path from_path __free(path_put) = {};
struct filename *to_name __free(putname) = NULL;
struct filename *from_name __free(putname) = NULL;
unsigned int lflags, uflags;
enum mnt_tree_flags_t mflags = 0;
int ret = 0;
if (!may_mount())
@ -4415,43 +4434,51 @@ SYSCALL_DEFINE5(move_mount,
(MOVE_MOUNT_BENEATH | MOVE_MOUNT_SET_GROUP))
return -EINVAL;
/* If someone gives a pathname, they aren't permitted to move
* from an fd that requires unmount as we can't get at the flag
* to clear it afterwards.
*/
if (flags & MOVE_MOUNT_SET_GROUP) mflags |= MNT_TREE_PROPAGATION;
if (flags & MOVE_MOUNT_BENEATH) mflags |= MNT_TREE_BENEATH;
lflags = 0;
if (flags & MOVE_MOUNT_F_SYMLINKS) lflags |= LOOKUP_FOLLOW;
if (flags & MOVE_MOUNT_F_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
if (flags & MOVE_MOUNT_F_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
ret = user_path_at(from_dfd, from_pathname, lflags, &from_path);
if (ret < 0)
return ret;
if (flags & MOVE_MOUNT_F_EMPTY_PATH) uflags = AT_EMPTY_PATH;
from_name = getname_maybe_null(from_pathname, uflags);
if (IS_ERR(from_name))
return PTR_ERR(from_name);
lflags = 0;
if (flags & MOVE_MOUNT_T_SYMLINKS) lflags |= LOOKUP_FOLLOW;
if (flags & MOVE_MOUNT_T_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
if (flags & MOVE_MOUNT_T_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
if (flags & MOVE_MOUNT_T_EMPTY_PATH) uflags = AT_EMPTY_PATH;
to_name = getname_maybe_null(to_pathname, uflags);
if (IS_ERR(to_name))
return PTR_ERR(to_name);
ret = user_path_at(to_dfd, to_pathname, lflags, &to_path);
if (ret < 0)
goto out_from;
if (!to_name && to_dfd >= 0) {
CLASS(fd_raw, f_to)(to_dfd);
if (fd_empty(f_to))
return -EBADF;
ret = security_move_mount(&from_path, &to_path);
if (ret < 0)
goto out_to;
to_path = fd_file(f_to)->f_path;
path_get(&to_path);
} else {
ret = filename_lookup(to_dfd, to_name, lflags, &to_path, NULL);
if (ret)
return ret;
}
if (flags & MOVE_MOUNT_SET_GROUP)
ret = do_set_group(&from_path, &to_path);
else
ret = do_move_mount(&from_path, &to_path,
(flags & MOVE_MOUNT_BENEATH));
if (!from_name && from_dfd >= 0) {
CLASS(fd_raw, f_from)(from_dfd);
if (fd_empty(f_from))
return -EBADF;
out_to:
path_put(&to_path);
out_from:
path_put(&from_path);
return ret;
return vfs_move_mount(&fd_file(f_from)->f_path, &to_path, mflags);
}
ret = filename_lookup(from_dfd, from_name, lflags, &from_path, NULL);
if (ret)
return ret;
return vfs_move_mount(&from_path, &to_path, mflags);
}
/*

1
include/linux/fs.h
View File

@ -2855,6 +2855,7 @@ static inline struct filename *getname_maybe_null(const char __user *name, int f
return __getname_maybe_null(name);
}
extern void putname(struct filename *name);
DEFINE_FREE(putname, struct filename *, if (!IS_ERR_OR_NULL(_T)) putname(_T))
extern int finish_open(struct file *file, struct dentry *dentry,
int (*open)(struct inode *, struct file *));