Making shares unaccessible at root level mountable (aka solving bsc#8950 ...again)

Message ID	20160610171649.3e12b95c@aaptelpc (mailing list archive)
State	New, archived
Headers	show Return-Path: <linux-cifs-owner@kernel.org> Date: Fri, 10 Jun 2016 17:16:49 +0200 From: =?UTF-8?B?QXVyw6lsaWVu?= Aptel <aaptel@suse.com> To: Marcus Hoffmann <marcus.hoffmann@fu-berlin.de> Cc: linux-cifs <linux-cifs@vger.kernel.org>, samba-technical@lists.samba.org, Steve French <smfrench@gmail.com> Subject: Re: [PATCH] Making shares unaccessible at root level mountable (aka solving bsc#8950 ...again) Message-ID: <20160610171649.3e12b95c@aaptelpc> In-Reply-To: <5759C326.5040508@fu-berlin.de> References: <20160527194346.08416d79@aaptelpc> <20160609185027.7349f260@aaptelpc> <5759C326.5040508@fu-berlin.de> Organization: SUSE MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; boundary="Sig_/pFooELJ0g+oLseyMZQtgxIz"; protocol="application/pgp-signature" Sender: linux-cifs-owner@vger.kernel.org Precedence: bulk

From e858c28b7bf9b1c76c0a9703727c7bd02bf4a434 Mon Sep 17 00:00:00 2001 From: Aurelien Aptel <aaptel@suse.com> Date: Wed, 25 May 2016 19:59:09 +0200 Subject: [PATCH] fs/cifs: make share unaccessible at root level mountable if, when mounting //HOST/share/sub/dir/foo we can query /sub/dir/foo but not any of the path components above: - store the /sub/dir/foo prefix in the cifs super_block info - in the superblock, set root dentry to the subpath dentry (instead of the share root) - set a flag in the superblock to remember it - use prefixpath when building path from a dentry fixes bso#8950 Signed-off-by: Aurelien Aptel <aaptel@suse.com> --- fs/cifs/cifs_fs_sb.h | 2 ++ fs/cifs/cifsfs.c | 15 ++++++++++++++- fs/cifs/connect.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++ fs/cifs/dir.c | 19 +++++++++++++++++-- fs/cifs/inode.c | 17 +++++++++++++++-- 5 files changed, 95 insertions(+), 5 deletions(-) diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h index 3182273..02b9ac3 100644 --- a/fs/cifs/cifs_fs_sb.h +++ b/fs/cifs/cifs_fs_sb.h @@ -46,6 +46,7 @@ #define CIFS_MOUNT_CIFS_BACKUPUID 0x200000 /* backup intent bit for a user */ #define CIFS_MOUNT_CIFS_BACKUPGID 0x400000 /* backup intent bit for a group */ #define CIFS_MOUNT_MAP_SFM_CHR 0x800000 /* SFM/MAC mapping for illegal chars */ +#define CIFS_MOUNT_USE_PREFIX_PATH 0x1000000 /* make subpath with unaccessible root mountable */ struct cifs_sb_info { struct rb_root tlink_tree; @@ -67,5 +68,6 @@ struct cifs_sb_info { struct backing_dev_info bdi; struct delayed_work prune_tlinks; struct rcu_head rcu; + char *prepath; }; #endif /* _CIFS_FS_SB_H */ diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c index 5d8b7ed..c75d80c 100644 --- a/fs/cifs/cifsfs.c +++ b/fs/cifs/cifsfs.c @@ -649,6 +649,7 @@ cifs_get_root(struct smb_vol *vol, struct super_block *sb) dentry = child; } while (!IS_ERR(dentry)); kfree(full_path); + return dentry; } @@ -688,6 +689,14 @@ cifs_do_mount(struct file_system_type *fs_type, goto out_cifs_sb; } + if (volume_info->prepath) { + cifs_sb->prepath = kstrdup(volume_info->prepath, GFP_KERNEL); + if (cifs_sb->prepath == NULL) { + root = ERR_PTR(-ENOMEM); + goto out_cifs_sb; + } + } + cifs_setup_cifs_sb(volume_info, cifs_sb); rc = cifs_mount(cifs_sb, volume_info); @@ -726,7 +735,11 @@ cifs_do_mount(struct file_system_type *fs_type, sb->s_flags |= MS_ACTIVE; } - root = cifs_get_root(volume_info, sb); + if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH) { + root = dget(sb->s_root); + } else { + root = cifs_get_root(volume_info, sb); + } if (IS_ERR(root)) goto out_super; diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index 66736f5..b82d7b4 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -3481,6 +3481,42 @@ cifs_get_volume_info(char *mount_data, const char *devname) return volume_info; } +static int +cifs_are_all_path_components_accessible(struct TCP_Server_Info *server, + unsigned int xid, + struct cifs_tcon *tcon, + struct cifs_sb_info *cifs_sb, + char *full_path) +{ + int rc; + char *s; + char sep, tmp; + + sep = CIFS_DIR_SEP(cifs_sb); + s = full_path; + + rc = server->ops->is_path_accessible(xid, tcon, cifs_sb, ""); + while (rc == 0) { + /* skip separators */ + while (*s == sep) + s++; + if (!*s) + break; + + /* next separator */ + while (*s && *s != sep) + s++; + + /* temporarily null-terminate the path at the end of + * the current component */ + tmp = *s; + *s = 0; + rc = server->ops->is_path_accessible(xid, tcon, cifs_sb, full_path); + *s = tmp; + } + return rc; +} + int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info) { @@ -3618,6 +3654,14 @@ remote_path_check: kfree(full_path); goto mount_fail_check; } + + rc = cifs_are_all_path_components_accessible(server, xid, tcon, cifs_sb, full_path); + if (rc != 0) { + cifs_dbg(VFS, "cannot query directories between root and final path, " + "enabling CIFS_MOUNT_USE_PREFIX_PATH\n"); + cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_USE_PREFIX_PATH; + rc = 0; + } kfree(full_path); } @@ -3887,6 +3931,9 @@ cifs_umount(struct cifs_sb_info *cifs_sb) bdi_destroy(&cifs_sb->bdi); kfree(cifs_sb->mountdata); + if (cifs_sb->prepath) { + kfree(cifs_sb->prepath); + } call_rcu(&cifs_sb->rcu, delayed_free); } diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c index c3eb998..5374253 100644 --- a/fs/cifs/dir.c +++ b/fs/cifs/dir.c @@ -84,6 +84,7 @@ build_path_from_dentry(struct dentry *direntry) struct dentry *temp; int namelen; int dfsplen; + int pplen = 0; char *full_path; char dirsep; struct cifs_sb_info *cifs_sb = CIFS_SB(direntry->d_sb); @@ -95,8 +96,12 @@ build_path_from_dentry(struct dentry *direntry) dfsplen = strnlen(tcon->treeName, MAX_TREE_SIZE + 1); else dfsplen = 0; + + if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH) + pplen = cifs_sb->prepath ? strlen(cifs_sb->prepath) + 1 : 0; + cifs_bp_rename_retry: - namelen = dfsplen; + namelen = dfsplen + pplen; seq = read_seqbegin(&rename_lock); rcu_read_lock(); for (temp = direntry; !IS_ROOT(temp);) { @@ -137,7 +142,7 @@ cifs_bp_rename_retry: } } rcu_read_unlock(); - if (namelen != dfsplen || read_seqretry(&rename_lock, seq)) { + if (namelen != dfsplen + pplen || read_seqretry(&rename_lock, seq)) { cifs_dbg(FYI, "did not end path lookup where expected. namelen=%ddfsplen=%d\n", namelen, dfsplen); /* presumably this is only possible if racing with a rename @@ -153,6 +158,16 @@ cifs_bp_rename_retry: those safely to '/' if any are found in the middle of the prepath */ /* BB test paths to Windows with '/' in the midst of prepath */ + if (pplen) { + int i; + cifs_dbg(FYI, "using cifs_sb prepath <%s>\n", cifs_sb->prepath); + memcpy(full_path+dfsplen+1, cifs_sb->prepath, pplen-1); + full_path[dfsplen] = '\\'; + for (i = 0; i < pplen-1; i++) + if (full_path[dfsplen+1+i] == '/') + full_path[dfsplen+1+i] = CIFS_DIR_SEP(cifs_sb); + } + if (dfsplen) { strncpy(full_path, tcon->treeName, dfsplen); if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) { diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c index 514dadb..7c6edd7 100644 --- a/fs/cifs/inode.c +++ b/fs/cifs/inode.c @@ -1002,10 +1002,21 @@ struct inode *cifs_root_iget(struct super_block *sb) struct inode *inode = NULL; long rc; struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb); + char *path = NULL; + int len; + + if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH) && cifs_sb->prepath) { + len = strlen(cifs_sb->prepath); + path = kzalloc(len + 2 /* leading sep + null */, GFP_KERNEL); + path[0] = '/'; + memcpy(path+1, cifs_sb->prepath, len); + } else { + path = kstrdup("", GFP_KERNEL); + } xid = get_xid(); if (tcon->unix_ext) { - rc = cifs_get_inode_info_unix(&inode, "", sb, xid); + rc = cifs_get_inode_info_unix(&inode, path, sb, xid); /* some servers mistakenly claim POSIX support */ if (rc != -EOPNOTSUPP) goto iget_no_retry; @@ -1013,7 +1024,8 @@ struct inode *cifs_root_iget(struct super_block *sb) tcon->unix_ext = false; } - rc = cifs_get_inode_info(&inode, "", NULL, sb, xid, NULL); + convert_delimiter(path, CIFS_DIR_SEP(cifs_sb)); + rc = cifs_get_inode_info(&inode, path, NULL, sb, xid, NULL); iget_no_retry: if (!inode) { @@ -1042,6 +1054,7 @@ iget_no_retry: } out: + kfree(path); /* can not call macro free_xid here since in a void func * TODO: This is no longer true */ -- 2.1.4

Making shares unaccessible at root level mountable (aka solving bsc#8950 ...again)

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