[PATCH 1/4] userns: Allow for fuse filesystems outside the initial user namespace

[Eric W. Biederman]

Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
---
 fs/fuse/dev.c    | 10 +++++-----
 fs/fuse/dir.c    | 41 ++++++++++++++++++++++++++++++-----------
 fs/fuse/fuse_i.h |  3 +++
 fs/fuse/inode.c  | 10 ++++++++--
 4 files changed, 46 insertions(+), 18 deletions(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index ca887314aba9..e01f30c51b3c 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -124,10 +124,10 @@ static void __fuse_put_request(struct fuse_req *req)
 	atomic_dec(&req->count);
 }
 
-static void fuse_req_init_context(struct fuse_req *req)
+static void fuse_req_init_context(struct fuse_conn *fc, struct fuse_req *req)
 {
-	req->in.h.uid = from_kuid_munged(&init_user_ns, current_fsuid());
-	req->in.h.gid = from_kgid_munged(&init_user_ns, current_fsgid());
+	req->in.h.uid = from_kuid_munged(fc->user_ns, current_fsuid());
+	req->in.h.gid = from_kgid_munged(fc->user_ns, current_fsgid());
 	req->in.h.pid = current->pid;
 }
 
@@ -168,7 +168,7 @@ static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages,
 		goto out;
 	}
 
-	fuse_req_init_context(req);
+	fuse_req_init_context(fc, req);
 	req->waiting = 1;
 	req->background = for_background;
 	return req;
@@ -257,7 +257,7 @@ struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
 	if (!req)
 		req = get_reserved_req(fc, file);
 
-	fuse_req_init_context(req);
+	fuse_req_init_context(fc, req);
 	req->waiting = 1;
 	req->background = 0;
 	return req;
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index de1d84af9f7c..d74c75a057cd 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -886,7 +886,7 @@ static int fuse_link(struct dentry *entry, struct inode *newdir,
 	return err;
 }
 
-static void fuse_fillattr(struct inode *inode, struct fuse_attr *attr,
+static int fuse_fillattr(struct inode *inode, struct fuse_attr *attr,
 			  struct kstat *stat)
 {
 	unsigned int blkbits;
@@ -905,8 +905,12 @@ static void fuse_fillattr(struct inode *inode, struct fuse_attr *attr,
 	stat->ino = attr->ino;
 	stat->mode = (inode->i_mode & S_IFMT) | (attr->mode & 07777);
 	stat->nlink = attr->nlink;
-	stat->uid = make_kuid(&init_user_ns, attr->uid);
-	stat->gid = make_kgid(&init_user_ns, attr->gid);
+	stat->uid = make_kuid(fc->user_ns, attr->uid);
+	if (!uid_valid(stat->uid))
+		return -EOVERFLOW;
+	stat->gid = make_kgid(fc->user_ns, attr->gid);
+	if (!gid_valid(stat->gid))
+		return -EOVERFLOW;
 	stat->rdev = inode->i_rdev;
 	stat->atime.tv_sec = attr->atime;
 	stat->atime.tv_nsec = attr->atimensec;
@@ -923,6 +927,7 @@ static void fuse_fillattr(struct inode *inode, struct fuse_attr *attr,
 		blkbits = inode->i_sb->s_blocksize_bits;
 
 	stat->blksize = 1 << blkbits;
+	return 0;
 }
 
 static int fuse_do_getattr(struct inode *inode, struct kstat *stat,
@@ -973,7 +978,8 @@ static int fuse_do_getattr(struct inode *inode, struct kstat *stat,
 					       attr_timeout(&outarg),
 					       attr_version);
 			if (stat)
-				fuse_fillattr(inode, &outarg.attr, stat);
+				err = fuse_fillattr(inode, &outarg.attr,
+						    stat);
 		}
 	}
 	return err;
@@ -1556,17 +1562,25 @@ static bool update_mtime(unsigned ivalid, bool trust_local_mtime)
 	return true;
 }
 
-static void iattr_to_fattr(struct iattr *iattr, struct fuse_setattr_in *arg,
-			   bool trust_local_cmtime)
+static int iattr_to_fattr(struct fuse_conn *fc, struct iattr *iattr,
+			   struct fuse_setattr_in *arg, bool trust_local_cmtime)
 {
 	unsigned ivalid = iattr->ia_valid;
 
 	if (ivalid & ATTR_MODE)
 		arg->valid |= FATTR_MODE,   arg->mode = iattr->ia_mode;
-	if (ivalid & ATTR_UID)
-		arg->valid |= FATTR_UID,    arg->uid = from_kuid(&init_user_ns, iattr->ia_uid);
-	if (ivalid & ATTR_GID)
-		arg->valid |= FATTR_GID,    arg->gid = from_kgid(&init_user_ns, iattr->ia_gid);
+	if (ivalid & ATTR_UID) {
+		arg->valid |= FATTR_UID;
+		arg->uid = from_kuid(fc->user_ns, iattr->ia_uid);
+		if (arg->uid == (uid_t)-1)
+			return -EOVERFLOW;
+	}
+	if (ivalid & ATTR_GID) {
+		arg->valid |= FATTR_GID;
+		arg->gid = from_kgid(fc->user_ns, iattr->ia_gid);
+		if (arg->gid == (gid_t)-1)
+			return -EOVERFLOW;
+	}
 	if (ivalid & ATTR_SIZE)
 		arg->valid |= FATTR_SIZE,   arg->size = iattr->ia_size;
 	if (ivalid & ATTR_ATIME) {
@@ -1588,6 +1602,7 @@ static void iattr_to_fattr(struct iattr *iattr, struct fuse_setattr_in *arg,
 		arg->ctime = iattr->ia_ctime.tv_sec;
 		arg->ctimensec = iattr->ia_ctime.tv_nsec;
 	}
+	return 0;
 }
 
 /*
@@ -1741,7 +1756,11 @@ int fuse_do_setattr(struct inode *inode, struct iattr *attr,
 
 	memset(&inarg, 0, sizeof(inarg));
 	memset(&outarg, 0, sizeof(outarg));
-	iattr_to_fattr(attr, &inarg, trust_local_cmtime);
+	err = iattr_to_fattr(fc, attr, &inarg, trust_local_cmtime);
+	if (err) {
+		goto error;
+	}
+
 	if (file) {
 		struct fuse_file *ff = file->private_data;
 		inarg.valid |= FATTR_FH;
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index e8e47a6ab518..e7dbbb5d62b4 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -598,6 +598,9 @@ struct fuse_conn {
 
 	/** Read/write semaphore to hold when accessing sb. */
 	struct rw_semaphore killsb;
+
+	/** User namespace to communicate uids and gids to the fuse daemon */
+	struct user_namespace *user_ns;
 };
 
 static inline struct fuse_conn *get_fuse_conn_super(struct super_block *sb)
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 03246cd9d47a..894288f7ad67 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -20,6 +20,7 @@
 #include <linux/random.h>
 #include <linux/sched.h>
 #include <linux/exportfs.h>
+#include <linux/user_namespace.h>
 
 MODULE_AUTHOR("Miklos Szeredi <miklos@xxxxxxxxxx>");
 MODULE_DESCRIPTION("Filesystem in Userspace");
@@ -577,8 +578,8 @@ static int fuse_show_options(struct seq_file *m, struct dentry *root)
 	struct super_block *sb = root->d_sb;
 	struct fuse_conn *fc = get_fuse_conn_super(sb);
 
-	seq_printf(m, ",user_id=%u", from_kuid_munged(&init_user_ns, fc->user_id));
-	seq_printf(m, ",group_id=%u", from_kgid_munged(&init_user_ns, fc->group_id));
+	seq_printf(m, ",user_id=%u", from_kuid_munged(fc->user_ns, fc->user_id));
+	seq_printf(m, ",group_id=%u", from_kgid_munged(fc->user_ns, fc->group_id));
 	if (fc->flags & FUSE_DEFAULT_PERMISSIONS)
 		seq_puts(m, ",default_permissions");
 	if (fc->flags & FUSE_ALLOW_OTHER)
@@ -616,6 +617,7 @@ void fuse_conn_init(struct fuse_conn *fc)
 	fc->initialized = 0;
 	fc->attr_version = 1;
 	get_random_bytes(&fc->scramble_key, sizeof(fc->scramble_key));
+	fc->user_ns = get_user_ns(current_user_ns());
 }
 EXPORT_SYMBOL_GPL(fuse_conn_init);
 
@@ -624,6 +626,8 @@ void fuse_conn_put(struct fuse_conn *fc)
 	if (atomic_dec_and_test(&fc->count)) {
 		if (fc->destroy_req)
 			fuse_request_free(fc->destroy_req);
+		put_user_ns(fc->user_ns);
+		fc->user_ns = NULL;
 		fc->release(fc);
 	}
 }
@@ -1033,6 +1037,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_maxbytes = MAX_LFS_FILESIZE;
 	sb->s_time_gran = 1;
 	sb->s_export_op = &fuse_export_operations;
+	sb->s_user_ns = get_user_ns(current_user_ns());
 
 	file = fget(d.fd);
 	err = -EINVAL;
@@ -1149,6 +1154,7 @@ static void fuse_kill_sb_anon(struct super_block *sb)
 	}
 
 	kill_anon_super(sb);
+	put_user_ns(sb->s_user_ns);
 }
 
 static struct file_system_type fuse_fs_type = {
-- 
1.9.1


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 filename=0002-fuse-Teach-fuse-how-to-handle-the-pid-namespace.patch