// SPDX-License-Identifier: GPL-2.0-or-later /* * Contains mounting routines used for handling traversal via SMB junctions. * * Copyright (c) 2007 Igor Mammedov * Copyright (C) International Business Machines Corp., 2008 * Author(s): Igor Mammedov (niallain@gmail.com) * Steve French (sfrench@us.ibm.com) * Copyright (c) 2023 Paulo Alcantara */ #include #include #include #include #include #include #include #include "cifsglob.h" #include "cifsproto.h" #include "cifsfs.h" #include "cifs_debug.h" #include "fs_context.h" static LIST_HEAD(cifs_automount_list); static void cifs_expire_automounts(struct work_struct *work); static DECLARE_DELAYED_WORK(cifs_automount_task, cifs_expire_automounts); static int cifs_mountpoint_expiry_timeout = 500 * HZ; static void cifs_expire_automounts(struct work_struct *work) { struct list_head *list = &cifs_automount_list; mark_mounts_for_expiry(list); if (!list_empty(list)) schedule_delayed_work(&cifs_automount_task, cifs_mountpoint_expiry_timeout); } void cifs_release_automount_timer(void) { if (WARN_ON(!list_empty(&cifs_automount_list))) return; cancel_delayed_work_sync(&cifs_automount_task); } /** * cifs_build_devname - build a devicename from a UNC and optional prepath * @nodename: pointer to UNC string * @prepath: pointer to prefixpath (or NULL if there isn't one) * * Build a new cifs devicename after chasing a DFS referral. Allocate a buffer * big enough to hold the final thing. Copy the UNC from the nodename, and * concatenate the prepath onto the end of it if there is one. * * Returns pointer to the built string, or a ERR_PTR. Caller is responsible * for freeing the returned string. */ char * cifs_build_devname(char *nodename, const char *prepath) { size_t pplen; size_t unclen; char *dev; char *pos; /* skip over any preceding delimiters */ nodename += strspn(nodename, "\\"); if (!*nodename) return ERR_PTR(-EINVAL); /* get length of UNC and set pos to last char */ unclen = strlen(nodename); pos = nodename + unclen - 1; /* trim off any trailing delimiters */ while (*pos == '\\') { --pos; --unclen; } /* allocate a buffer: * +2 for preceding "//" * +1 for delimiter between UNC and prepath * +1 for trailing NULL */ pplen = prepath ? strlen(prepath) : 0; dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL); if (!dev) return ERR_PTR(-ENOMEM); pos = dev; /* add the initial "//" */ *pos = '/'; ++pos; *pos = '/'; ++pos; /* copy in the UNC portion from referral */ memcpy(pos, nodename, unclen); pos += unclen; /* copy the prefixpath remainder (if there is one) */ if (pplen) { *pos = '/'; ++pos; memcpy(pos, prepath, pplen); pos += pplen; } /* NULL terminator */ *pos = '\0'; convert_delimiter(dev, '/'); return dev; } static bool is_dfs_mount(struct dentry *dentry) { struct cifs_sb_info *cifs_sb = CIFS_SB(dentry->d_sb); struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb); bool ret; spin_lock(&tcon->tc_lock); ret = !!tcon->origin_fullpath; spin_unlock(&tcon->tc_lock); return ret; } /* Return full path out of a dentry set for automount */ static char *automount_fullpath(struct dentry *dentry, void *page) { struct cifs_sb_info *cifs_sb = CIFS_SB(dentry->d_sb); struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb); size_t len; char *s; spin_lock(&tcon->tc_lock); if (!tcon->origin_fullpath) { spin_unlock(&tcon->tc_lock); return build_path_from_dentry_optional_prefix(dentry, page, true); } spin_unlock(&tcon->tc_lock); s = dentry_path_raw(dentry, page, PATH_MAX); if (IS_ERR(s)) return s; /* for root, we want "" */ if (!s[1]) s++; spin_lock(&tcon->tc_lock); len = strlen(tcon->origin_fullpath); if (s < (char *)page + len) { spin_unlock(&tcon->tc_lock); return ERR_PTR(-ENAMETOOLONG); } s -= len; memcpy(s, tcon->origin_fullpath, len); spin_unlock(&tcon->tc_lock); convert_delimiter(s, '/'); return s; } static void fs_context_set_ids(struct smb3_fs_context *ctx) { kuid_t uid = current_fsuid(); kgid_t gid = current_fsgid(); if (ctx->multiuser) { if (!ctx->uid_specified) ctx->linux_uid = uid; if (!ctx->gid_specified) ctx->linux_gid = gid; } if (!ctx->cruid_specified) ctx->cred_uid = uid; } /* * Create a vfsmount that we can automount */ static struct vfsmount *cifs_do_automount(struct path *path) { int rc; struct dentry *mntpt = path->dentry; struct fs_context *fc; void *page = NULL; struct smb3_fs_context *ctx, *cur_ctx; struct smb3_fs_context tmp; char *full_path; struct vfsmount *mnt; if (IS_ROOT(mntpt)) return ERR_PTR(-ESTALE); cur_ctx = CIFS_SB(mntpt->d_sb)->ctx; fc = fs_context_for_submount(path->mnt->mnt_sb->s_type, mntpt); if (IS_ERR(fc)) return ERR_CAST(fc); ctx = smb3_fc2context(fc); page = alloc_dentry_path(); full_path = automount_fullpath(mntpt, page); if (IS_ERR(full_path)) { mnt = ERR_CAST(full_path); goto out; } tmp = *cur_ctx; tmp.source = NULL; tmp.leaf_fullpath = NULL; tmp.UNC = tmp.prepath = NULL; tmp.dfs_root_ses = NULL; fs_context_set_ids(&tmp); rc = smb3_fs_context_dup(ctx, &tmp); if (rc) { mnt = ERR_PTR(rc); goto out; } rc = smb3_parse_devname(full_path, ctx); if (rc) { mnt = ERR_PTR(rc); goto out; } ctx->source = smb3_fs_context_fullpath(ctx, '/'); if (IS_ERR(ctx->source)) { mnt = ERR_CAST(ctx->source); ctx->source = NULL; goto out; } ctx->dfs_automount = ctx->dfs_conn = is_dfs_mount(mntpt); cifs_dbg(FYI, "%s: ctx: source=%s UNC=%s prepath=%s dfs_automount=%d\n", __func__, ctx->source, ctx->UNC, ctx->prepath, ctx->dfs_automount); mnt = fc_mount(fc); out: put_fs_context(fc); free_dentry_path(page); return mnt; } /* * Attempt to automount the referral */ struct vfsmount *cifs_d_automount(struct path *path) { struct vfsmount *newmnt; cifs_dbg(FYI, "%s: %pd\n", __func__, path->dentry); newmnt = cifs_do_automount(path); if (IS_ERR(newmnt)) { cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__); return newmnt; } mntget(newmnt); /* prevent immediate expiration */ mnt_set_expiry(newmnt, &cifs_automount_list); schedule_delayed_work(&cifs_automount_task, cifs_mountpoint_expiry_timeout); cifs_dbg(FYI, "leaving %s [ok]\n" , __func__); return newmnt; } const struct inode_operations cifs_namespace_inode_operations = { };