From: Christian Brauner <christian.brauner@xxxxxxxxxx> commit bb49e9e730c2906a958eee273a7819f401543d6c upstream. 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@xxxxxxxxxx (v1) Link: https://lore.kernel.org/r/20211130121032.3753852-2-brauner@xxxxxxxxxx (v2) Link: https://lore.kernel.org/r/20211203111707.3901969-2-brauner@xxxxxxxxxx Cc: Seth Forshee <sforshee@xxxxxxxxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> CC: linux-fsdevel@xxxxxxxxxxxxxxx Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx> Reviewed-by: Seth Forshee <sforshee@xxxxxxxxxxxxxxxx> Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx> Signed-off-by: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx> --- fs/cachefiles/bind.c | 2 +- fs/ecryptfs/main.c | 2 +- fs/namespace.c | 2 +- fs/nfsd/export.c | 2 +- fs/overlayfs/super.c | 2 +- fs/proc_namespace.c | 2 +- include/linux/fs.h | 14 ++++++++++++++ 7 files changed, 20 insertions(+), 6 deletions(-) diff --git a/fs/cachefiles/bind.c b/fs/cachefiles/bind.c index d463d89f5db8..146291be6263 100644 --- a/fs/cachefiles/bind.c +++ b/fs/cachefiles/bind.c @@ -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; } diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c index d66bbd2df191..2dd23a82e0de 100644 --- a/fs/ecryptfs/main.c +++ b/fs/ecryptfs/main.c @@ -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; diff --git a/fs/namespace.c b/fs/namespace.c index b696543adab8..5b5aa107b9f3 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -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. */ diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c index 9421dae22737..668c7527b17e 100644 --- a/fs/nfsd/export.c +++ b/fs/nfsd/export.c @@ -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; } diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 265181c110ae..7bb0a47cb615 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -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; } diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c index 392ef5162655..49650e54d2f8 100644 --- a/fs/proc_namespace.c +++ b/fs/proc_namespace.c @@ -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"); } diff --git a/include/linux/fs.h b/include/linux/fs.h index 56eba723477e..5720473b94b1 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2726,6 +2726,20 @@ 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); -- 2.34.1
