[PATCH 01/10] fs: add is_mapped_mnt() helper
From: Christian Brauner <brauner@kernel.org>
Date: 2021-11-23 11:42:55
Subsystem:
cachefiles: fs-cache backend for caching on mounted filesystems, ecrypt file system, filesystems (vfs and infrastructure), kernel nfsd, sunrpc, and lockd servers, overlay filesystem, the rest · Maintainers:
David Howells, Tyler Hicks, Alexander Viro, Christian Brauner, Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein, Linus Torvalds
From: Christian Brauner <redacted> 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. Cc: Seth Forshee <redacted> Cc: Christoph Hellwig <hch@lst.de> Cc: Al Viro <viro@zeniv.linux.org.uk> CC: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner <redacted> --- 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..8130142d89c2 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_mapped_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..331ac3a59515 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_mapped_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 659a8f39c61a..7d7b80b375a4 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_mapped_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..292bde9e1eb3 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_mapped_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..113575fc6155 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_mapped_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..788c687bb052 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_mapped_mnt(mnt)) seq_puts(m, ",idmapped"); }
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1cb616fc1105..192242476b2b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h@@ -2725,6 +2725,20 @@ static inline struct user_namespace *file_mnt_user_ns(struct file *file) { return mnt_user_ns(file->f_path.mnt); } + +/** + * is_mapped_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_mapped_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);
--
2.30.2