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fs: add is_idmapped_mnt() helper 

Multiple places open-code the same check to determine whether a given
mount is idmapped. Introduce a simple helper function that can be used
instead. This allows us to get rid of the fragile open-coding. We will
later change the check that is used to determine whether a given mount
is idmapped. Introducing a helper allows us to do this in a single
place instead of doing it for multiple places.

Link: https://lore.kernel.org/r/20211123114227.3124056-2-brauner@kernel.org (v1)
Link: https://lore.kernel.org/r/20211130121032.3753852-2-brauner@kernel.org (v2)
Link: https://lore.kernel.org/r/20211203111707.3901969-2-brauner@kernel.org
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
CC: linux-fsdevel@vger.kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Seth Forshee <sforshee@digitalocean.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
This commit is contained in:
Christian Brauner 2021-12-03 12:16:58 +01:00
parent d58071a8a7
commit bb49e9e730
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
7 changed files with 20 additions and 6 deletions
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2
fs/cachefiles/bind.c
View File

@ -117,7 +117,7 @@ static int cachefiles_daemon_add_cache(struct cachefiles_cache *cache)
root = path.dentry;
ret = -EINVAL;
if (mnt_user_ns(path.mnt) != &init_user_ns) {
if (is_idmapped_mnt(path.mnt)) {
pr_warn("File cache on idmapped mounts not supported");
goto error_unsupported;
}

2
fs/ecryptfs/main.c
View File

@ -537,7 +537,7 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags
goto out_free;
}
if (mnt_user_ns(path.mnt) != &init_user_ns) {
if (is_idmapped_mnt(path.mnt)) {
rc = -EINVAL;
printk(KERN_ERR "Mounting on idmapped mounts currently disallowed\n");
goto out_free;

2
fs/namespace.c
View File

@ -3936,7 +3936,7 @@ static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
* mapping. It makes things simpler and callers can just create
* another bind-mount they can idmap if they want to.
*/
if (mnt_user_ns(m) != &init_user_ns)
if (is_idmapped_mnt(m))
return -EPERM;
/* The underlying filesystem doesn't support idmapped mounts yet. */

2
fs/nfsd/export.c
View File

@ -427,7 +427,7 @@ static int check_export(struct path *path, int *flags, unsigned char *uuid)
return -EINVAL;
}
if (mnt_user_ns(path->mnt) != &init_user_ns) {
if (is_idmapped_mnt(path->mnt)) {
dprintk("exp_export: export of idmapped mounts not yet supported.\n");
return -EINVAL;
}

2
fs/overlayfs/super.c
View File

@ -873,7 +873,7 @@ static int ovl_mount_dir_noesc(const char *name, struct path *path)
pr_err("filesystem on '%s' not supported\n", name);
goto out_put;
}
if (mnt_user_ns(path->mnt) != &init_user_ns) {
if (is_idmapped_mnt(path->mnt)) {
pr_err("idmapped layers are currently not supported\n");
goto out_put;
}

2
fs/proc_namespace.c
View File

@ -80,7 +80,7 @@ static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
seq_puts(m, fs_infop->str);
}
if (mnt_user_ns(mnt) != &init_user_ns)
if (is_idmapped_mnt(mnt))
seq_puts(m, ",idmapped");
}

14
include/linux/fs.h
View File

@ -2724,6 +2724,20 @@ static inline struct user_namespace *file_mnt_user_ns(struct file *file)
{
return mnt_user_ns(file->f_path.mnt);
}
/**
* is_idmapped_mnt - check whether a mount is mapped
* @mnt: the mount to check
*
* If @mnt has an idmapping attached to it @mnt is mapped.
*
* Return: true if mount is mapped, false if not.
*/
static inline bool is_idmapped_mnt(const struct vfsmount *mnt)
{
return mnt_user_ns(mnt) != &init_user_ns;
}
extern long vfs_truncate(const struct path *, loff_t);
int do_truncate(struct user_namespace *, struct dentry *, loff_t start,
unsigned int time_attrs, struct file *filp);