From 3b7008b226f3de811d4ac34238e9cf670f7c9fe7 Mon Sep 17 00:00:00 2001 From: Szymon Lukasz Date: Thu, 9 Nov 2017 21:23:35 +0100 Subject: fuse: return -ECONNABORTED on /dev/fuse read after abort Currently the userspace has no way of knowing whether the fuse connection ended because of umount or abort via sysfs. It makes it hard for filesystems to free the mountpoint after abort without worrying about removing some new mount. The patch fixes it by returning different errors when userspace reads from /dev/fuse (-ENODEV for umount and -ECONNABORTED for abort). Add a new capability flag FUSE_ABORT_ERROR. If set and the connection is gone because of sysfs abort, reading from the device will return -ECONNABORTED. Signed-off-by: Szymon Lukasz Signed-off-by: Miklos Szeredi --- fs/fuse/inode.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'fs/fuse/inode.c') diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 624f18bbfd2b..3c9b675d99da 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -371,7 +371,7 @@ void fuse_unlock_inode(struct inode *inode) static void fuse_umount_begin(struct super_block *sb) { - fuse_abort_conn(get_fuse_conn_super(sb)); + fuse_abort_conn(get_fuse_conn_super(sb), false); } static void fuse_send_destroy(struct fuse_conn *fc) @@ -393,7 +393,7 @@ static void fuse_put_super(struct super_block *sb) fuse_send_destroy(fc); - fuse_abort_conn(fc); + fuse_abort_conn(fc, false); mutex_lock(&fuse_mutex); list_del(&fc->entry); fuse_ctl_remove_conn(fc); @@ -918,6 +918,8 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req) fc->posix_acl = 1; fc->sb->s_xattr = fuse_acl_xattr_handlers; } + if (arg->flags & FUSE_ABORT_ERROR) + fc->abort_err = 1; } else { ra_pages = fc->max_read / PAGE_SIZE; fc->no_lock = 1; @@ -948,7 +950,8 @@ static void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req) FUSE_FLOCK_LOCKS | FUSE_HAS_IOCTL_DIR | FUSE_AUTO_INVAL_DATA | FUSE_DO_READDIRPLUS | FUSE_READDIRPLUS_AUTO | FUSE_ASYNC_DIO | FUSE_WRITEBACK_CACHE | FUSE_NO_OPEN_SUPPORT | - FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL; + FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL | + FUSE_ABORT_ERROR; req->in.h.opcode = FUSE_INIT; req->in.numargs = 1; req->in.args[0].size = sizeof(*arg); -- cgit v1.2.3 From 8cb08329b0809453722bc12aa912be34355bcb66 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Wed, 21 Feb 2018 11:18:07 -0600 Subject: fuse: Support fuse filesystems outside of init_user_ns In order to support mounts from namespaces other than init_user_ns, fuse must translate uids and gids to/from the userns of the process servicing requests on /dev/fuse. This patch does that, with a couple of restrictions on the namespace: - The userns for the fuse connection is fixed to the namespace from which /dev/fuse is opened. - The namespace must be the same as s_user_ns. These restrictions simplify the implementation by avoiding the need to pass around userns references and by allowing fuse to rely on the checks in setattr_prepare for ownership changes. Either restriction could be relaxed in the future if needed. For cuse the userns used is the opener of /dev/cuse. Semantically the cuse support does not appear safe for unprivileged users. Practically the permissions on /dev/cuse only make it accessible to the global root user. If something slips through the cracks in a user namespace the only users who will be able to use the cuse device are those users mapped into the user namespace. Translation in the posix acl is updated to use the uuser namespace of the filesystem. Avoiding cases which might bypass this translation is handled in a following change. This change is stronlgy based on a similar change from Seth Forshee and Dongsu Park. Cc: Seth Forshee Cc: Dongsu Park Signed-off-by: Eric W. Biederman Signed-off-by: Miklos Szeredi --- fs/fuse/acl.c | 4 ++-- fs/fuse/cuse.c | 7 ++++++- fs/fuse/dev.c | 8 ++++---- fs/fuse/dir.c | 14 +++++++------- fs/fuse/fuse_i.h | 6 +++++- fs/fuse/inode.c | 31 +++++++++++++++++++------------ 6 files changed, 43 insertions(+), 27 deletions(-) (limited to 'fs/fuse/inode.c') diff --git a/fs/fuse/acl.c b/fs/fuse/acl.c index ec85765502f1..5a48cee6d7d3 100644 --- a/fs/fuse/acl.c +++ b/fs/fuse/acl.c @@ -34,7 +34,7 @@ struct posix_acl *fuse_get_acl(struct inode *inode, int type) return ERR_PTR(-ENOMEM); size = fuse_getxattr(inode, name, value, PAGE_SIZE); if (size > 0) - acl = posix_acl_from_xattr(&init_user_ns, value, size); + acl = posix_acl_from_xattr(fc->user_ns, value, size); else if ((size == 0) || (size == -ENODATA) || (size == -EOPNOTSUPP && fc->no_getxattr)) acl = NULL; @@ -81,7 +81,7 @@ int fuse_set_acl(struct inode *inode, struct posix_acl *acl, int type) if (!value) return -ENOMEM; - ret = posix_acl_to_xattr(&init_user_ns, acl, value, size); + ret = posix_acl_to_xattr(fc->user_ns, acl, value, size); if (ret < 0) { kfree(value); return ret; diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c index 31d33b69957f..8f68181256c0 100644 --- a/fs/fuse/cuse.c +++ b/fs/fuse/cuse.c @@ -48,6 +48,7 @@ #include #include #include +#include #include "fuse_i.h" @@ -498,7 +499,11 @@ static int cuse_channel_open(struct inode *inode, struct file *file) if (!cc) return -ENOMEM; - fuse_conn_init(&cc->fc); + /* + * Limit the cuse channel to requests that can + * be represented in file->f_cred->user_ns. + */ + fuse_conn_init(&cc->fc, file->f_cred->user_ns); fud = fuse_dev_alloc(&cc->fc); if (!fud) { diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 4852f8803156..686631f12001 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -156,8 +156,8 @@ static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages, goto out; } - req->in.h.uid = from_kuid(&init_user_ns, current_fsuid()); - req->in.h.gid = from_kgid(&init_user_ns, current_fsgid()); + req->in.h.uid = from_kuid(fc->user_ns, current_fsuid()); + req->in.h.gid = from_kgid(fc->user_ns, current_fsgid()); req->in.h.pid = pid_nr_ns(task_pid(current), fc->pid_ns); __set_bit(FR_WAITING, &req->flags); @@ -257,8 +257,8 @@ struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc, if (!req) req = get_reserved_req(fc, file); - 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 = pid_nr_ns(task_pid(current), fc->pid_ns); __set_bit(FR_WAITING, &req->flags); diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 7a980b4462d9..cf8a1cd7a62e 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -858,8 +858,8 @@ 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); + stat->gid = make_kgid(fc->user_ns, attr->gid); stat->rdev = inode->i_rdev; stat->atime.tv_sec = attr->atime; stat->atime.tv_nsec = attr->atimensec; @@ -1475,17 +1475,17 @@ 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 void 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); + arg->valid |= FATTR_UID, arg->uid = from_kuid(fc->user_ns, iattr->ia_uid); if (ivalid & ATTR_GID) - arg->valid |= FATTR_GID, arg->gid = from_kgid(&init_user_ns, iattr->ia_gid); + arg->valid |= FATTR_GID, arg->gid = from_kgid(fc->user_ns, iattr->ia_gid); if (ivalid & ATTR_SIZE) arg->valid |= FATTR_SIZE, arg->size = iattr->ia_size; if (ivalid & ATTR_ATIME) { @@ -1657,7 +1657,7 @@ int fuse_do_setattr(struct dentry *dentry, struct iattr *attr, memset(&inarg, 0, sizeof(inarg)); memset(&outarg, 0, sizeof(outarg)); - iattr_to_fattr(attr, &inarg, trust_local_cmtime); + iattr_to_fattr(fc, attr, &inarg, trust_local_cmtime); 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 7d2e7deea64b..f630951df8dc 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -26,6 +26,7 @@ #include #include #include +#include /** Max number of pages that can be used in a single read request */ #define FUSE_MAX_PAGES_PER_REQ 32 @@ -466,6 +467,9 @@ struct fuse_conn { /** The pid namespace for this mount */ struct pid_namespace *pid_ns; + /** The user namespace for this mount */ + struct user_namespace *user_ns; + /** Maximum read size */ unsigned max_read; @@ -876,7 +880,7 @@ struct fuse_conn *fuse_conn_get(struct fuse_conn *fc); /** * Initialize fuse_conn */ -void fuse_conn_init(struct fuse_conn *fc); +void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns); /** * Release reference to fuse_conn diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 3c9b675d99da..1643043d4fe5 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -171,8 +171,8 @@ void fuse_change_attributes_common(struct inode *inode, struct fuse_attr *attr, inode->i_ino = fuse_squash_ino(attr->ino); inode->i_mode = (inode->i_mode & S_IFMT) | (attr->mode & 07777); set_nlink(inode, attr->nlink); - inode->i_uid = make_kuid(&init_user_ns, attr->uid); - inode->i_gid = make_kgid(&init_user_ns, attr->gid); + inode->i_uid = make_kuid(fc->user_ns, attr->uid); + inode->i_gid = make_kgid(fc->user_ns, attr->gid); inode->i_blocks = attr->blocks; inode->i_atime.tv_sec = attr->atime; inode->i_atime.tv_nsec = attr->atimensec; @@ -477,7 +477,8 @@ static int fuse_match_uint(substring_t *s, unsigned int *res) return err; } -static int parse_fuse_opt(char *opt, struct fuse_mount_data *d, int is_bdev) +static int parse_fuse_opt(char *opt, struct fuse_mount_data *d, int is_bdev, + struct user_namespace *user_ns) { char *p; memset(d, 0, sizeof(struct fuse_mount_data)); @@ -513,7 +514,7 @@ static int parse_fuse_opt(char *opt, struct fuse_mount_data *d, int is_bdev) case OPT_USER_ID: if (fuse_match_uint(&args[0], &uv)) return 0; - d->user_id = make_kuid(current_user_ns(), uv); + d->user_id = make_kuid(user_ns, uv); if (!uid_valid(d->user_id)) return 0; d->user_id_present = 1; @@ -522,7 +523,7 @@ static int parse_fuse_opt(char *opt, struct fuse_mount_data *d, int is_bdev) case OPT_GROUP_ID: if (fuse_match_uint(&args[0], &uv)) return 0; - d->group_id = make_kgid(current_user_ns(), uv); + d->group_id = make_kgid(user_ns, uv); if (!gid_valid(d->group_id)) return 0; d->group_id_present = 1; @@ -565,8 +566,8 @@ 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->default_permissions) seq_puts(m, ",default_permissions"); if (fc->allow_other) @@ -597,7 +598,7 @@ static void fuse_pqueue_init(struct fuse_pqueue *fpq) fpq->connected = 1; } -void fuse_conn_init(struct fuse_conn *fc) +void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns) { memset(fc, 0, sizeof(*fc)); spin_lock_init(&fc->lock); @@ -621,6 +622,7 @@ void fuse_conn_init(struct fuse_conn *fc) fc->attr_version = 1; get_random_bytes(&fc->scramble_key, sizeof(fc->scramble_key)); fc->pid_ns = get_pid_ns(task_active_pid_ns(current)); + fc->user_ns = get_user_ns(user_ns); } EXPORT_SYMBOL_GPL(fuse_conn_init); @@ -630,6 +632,7 @@ void fuse_conn_put(struct fuse_conn *fc) if (fc->destroy_req) fuse_request_free(fc->destroy_req); put_pid_ns(fc->pid_ns); + put_user_ns(fc->user_ns); fc->release(fc); } } @@ -1064,7 +1067,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent) sb->s_flags &= ~(SB_NOSEC | SB_I_VERSION); - if (!parse_fuse_opt(data, &d, is_bdev)) + if (!parse_fuse_opt(data, &d, is_bdev, sb->s_user_ns)) goto err; if (is_bdev) { @@ -1089,8 +1092,12 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent) if (!file) goto err; - if ((file->f_op != &fuse_dev_operations) || - (file->f_cred->user_ns != &init_user_ns)) + /* + * Require mount to happen from the same user namespace which + * opened /dev/fuse to prevent potential attacks. + */ + if (file->f_op != &fuse_dev_operations || + file->f_cred->user_ns != sb->s_user_ns) goto err_fput; fc = kmalloc(sizeof(*fc), GFP_KERNEL); @@ -1098,7 +1105,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent) if (!fc) goto err_fput; - fuse_conn_init(fc); + fuse_conn_init(fc, sb->s_user_ns); fc->release = fuse_free_conn; fud = fuse_dev_alloc(fc); -- cgit v1.2.3 From e45b2546e23c2d10f8585063a15c745a7603fac9 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Fri, 4 May 2018 11:47:28 -0500 Subject: fuse: Ensure posix acls are translated outside of init_user_ns Ensure the translation happens by failing to read or write posix acls when the filesystem has not indicated it supports posix acls. This ensures that modern cached posix acl support is available and used when dealing with posix acls. This is important because only that path has the code to convernt the uids and gids in posix acls into the user namespace of a fuse filesystem. Signed-off-by: "Eric W. Biederman" Signed-off-by: Miklos Szeredi --- fs/fuse/fuse_i.h | 1 + fs/fuse/inode.c | 7 +++++++ fs/fuse/xattr.c | 43 +++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 51 insertions(+) (limited to 'fs/fuse/inode.c') diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index f630951df8dc..5256ad333b05 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -985,6 +985,7 @@ ssize_t fuse_listxattr(struct dentry *entry, char *list, size_t size); int fuse_removexattr(struct inode *inode, const char *name); extern const struct xattr_handler *fuse_xattr_handlers[]; extern const struct xattr_handler *fuse_acl_xattr_handlers[]; +extern const struct xattr_handler *fuse_no_acl_xattr_handlers[]; struct posix_acl; struct posix_acl *fuse_get_acl(struct inode *inode, int type); diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 1643043d4fe5..22c76cf8c2e3 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -1100,6 +1100,13 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent) file->f_cred->user_ns != sb->s_user_ns) goto err_fput; + /* + * If we are not in the initial user namespace posix + * acls must be translated. + */ + if (sb->s_user_ns != &init_user_ns) + sb->s_xattr = fuse_no_acl_xattr_handlers; + fc = kmalloc(sizeof(*fc), GFP_KERNEL); err = -ENOMEM; if (!fc) diff --git a/fs/fuse/xattr.c b/fs/fuse/xattr.c index 3caac46b08b0..433717640f78 100644 --- a/fs/fuse/xattr.c +++ b/fs/fuse/xattr.c @@ -192,6 +192,26 @@ static int fuse_xattr_set(const struct xattr_handler *handler, return fuse_setxattr(inode, name, value, size, flags); } +static bool no_xattr_list(struct dentry *dentry) +{ + return false; +} + +static int no_xattr_get(const struct xattr_handler *handler, + struct dentry *dentry, struct inode *inode, + const char *name, void *value, size_t size) +{ + return -EOPNOTSUPP; +} + +static int no_xattr_set(const struct xattr_handler *handler, + struct dentry *dentry, struct inode *nodee, + const char *name, const void *value, + size_t size, int flags) +{ + return -EOPNOTSUPP; +} + static const struct xattr_handler fuse_xattr_handler = { .prefix = "", .get = fuse_xattr_get, @@ -209,3 +229,26 @@ const struct xattr_handler *fuse_acl_xattr_handlers[] = { &fuse_xattr_handler, NULL }; + +static const struct xattr_handler fuse_no_acl_access_xattr_handler = { + .name = XATTR_NAME_POSIX_ACL_ACCESS, + .flags = ACL_TYPE_ACCESS, + .list = no_xattr_list, + .get = no_xattr_get, + .set = no_xattr_set, +}; + +static const struct xattr_handler fuse_no_acl_default_xattr_handler = { + .name = XATTR_NAME_POSIX_ACL_DEFAULT, + .flags = ACL_TYPE_ACCESS, + .list = no_xattr_list, + .get = no_xattr_get, + .set = no_xattr_set, +}; + +const struct xattr_handler *fuse_no_acl_xattr_handlers[] = { + &fuse_no_acl_access_xattr_handler, + &fuse_no_acl_default_xattr_handler, + &fuse_xattr_handler, + NULL +}; -- cgit v1.2.3 From 4ad769f3c346ec3d458e255548dec26ca5284cf6 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Tue, 29 May 2018 09:04:46 -0500 Subject: fuse: Allow fully unprivileged mounts Now that the fuse and the vfs work is complete. Allow the fuse filesystem to be mounted by the root user in a user namespace. Signed-off-by: "Eric W. Biederman" Signed-off-by: Miklos Szeredi --- fs/fuse/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/fuse/inode.c') diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 22c76cf8c2e3..48baa26993f3 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -1222,7 +1222,7 @@ static void fuse_kill_sb_anon(struct super_block *sb) static struct file_system_type fuse_fs_type = { .owner = THIS_MODULE, .name = "fuse", - .fs_flags = FS_HAS_SUBTYPE, + .fs_flags = FS_HAS_SUBTYPE | FS_USERNS_MOUNT, .mount = fuse_mount, .kill_sb = fuse_kill_sb_anon, }; -- cgit v1.2.3 From 543b8f8662fe6d21f19958b666ab0051af9db21a Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Tue, 1 May 2018 13:12:14 +0900 Subject: fuse: don't keep dead fuse_conn at fuse_fill_super(). syzbot is reporting use-after-free at fuse_kill_sb_blk() [1]. Since sb->s_fs_info field is not cleared after fc was released by fuse_conn_put() when initialization failed, fuse_kill_sb_blk() finds already released fc and tries to hold the lock. Fix this by clearing sb->s_fs_info field after calling fuse_conn_put(). [1] https://syzkaller.appspot.com/bug?id=a07a680ed0a9290585ca424546860464dd9658db Signed-off-by: Tetsuo Handa Reported-by: syzbot Fixes: 3b463ae0c626 ("fuse: invalidation reverse calls") Cc: John Muir Cc: Csaba Henk Cc: Anand Avati Cc: # v2.6.31 Signed-off-by: Miklos Szeredi --- fs/fuse/inode.c | 1 + 1 file changed, 1 insertion(+) (limited to 'fs/fuse/inode.c') diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 48baa26993f3..061500c72608 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -1193,6 +1193,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent) fuse_dev_free(fud); err_put_conn: fuse_conn_put(fc); + sb->s_fs_info = NULL; err_fput: fput(file); err: -- cgit v1.2.3