From patchwork Tue Oct 20 21:35:13 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kamal Mostafa X-Patchwork-Id: 533361 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) by ozlabs.org (Postfix) with ESMTP id C5A181401DE; Wed, 21 Oct 2015 08:42:51 +1100 (AEDT) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1ZoegB-0005Nb-Q4; Tue, 20 Oct 2015 21:42:47 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1ZoeZz-0001sQ-WF for kernel-team@lists.ubuntu.com; Tue, 20 Oct 2015 21:36:24 +0000 Received: from 1.general.kamal.us.vpn ([10.172.68.52] helo=fourier) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.76) (envelope-from ) id 1ZoeZz-0002DR-F8; Tue, 20 Oct 2015 21:36:23 +0000 Received: from kamal by fourier with local (Exim 4.82) (envelope-from ) id 1ZoeZx-00024N-8N; Tue, 20 Oct 2015 14:36:21 -0700 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Subject: [PATCH 3.13.y-ckt 57/85] fs: create and use seq_show_option for escaping Date: Tue, 20 Oct 2015 14:35:13 -0700 Message-Id: <1445376941-7046-58-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1445376941-7046-1-git-send-email-kamal@canonical.com> References: <1445376941-7046-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Cc: Kees Cook , Kamal Mostafa , Andrew Morton , Linus Torvalds , "J. R. Okajima" X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.14 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: kernel-team-bounces@lists.ubuntu.com 3.13.11-ckt28 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Kees Cook commit a068acf2ee77693e0bf39d6e07139ba704f461c3 upstream. Many file systems that implement the show_options hook fail to correctly escape their output which could lead to unescaped characters (e.g. new lines) leaking into /proc/mounts and /proc/[pid]/mountinfo files. This could lead to confusion, spoofed entries (resulting in things like systemd issuing false d-bus "mount" notifications), and who knows what else. This looks like it would only be the root user stepping on themselves, but it's possible weird things could happen in containers or in other situations with delegated mount privileges. Here's an example using overlay with setuid fusermount trusting the contents of /proc/mounts (via the /etc/mtab symlink). Imagine the use of "sudo" is something more sneaky: $ BASE="ovl" $ MNT="$BASE/mnt" $ LOW="$BASE/lower" $ UP="$BASE/upper" $ WORK="$BASE/work/ 0 0 none /proc fuse.pwn user_id=1000" $ mkdir -p "$LOW" "$UP" "$WORK" $ sudo mount -t overlay -o "lowerdir=$LOW,upperdir=$UP,workdir=$WORK" none /mnt $ cat /proc/mounts none /root/ovl/mnt overlay rw,relatime,lowerdir=ovl/lower,upperdir=ovl/upper,workdir=ovl/work/ 0 0 none /proc fuse.pwn user_id=1000 0 0 $ fusermount -u /proc $ cat /proc/mounts cat: /proc/mounts: No such file or directory This fixes the problem by adding new seq_show_option and seq_show_option_n helpers, and updating the vulnerable show_option handlers to use them as needed. Some, like SELinux, need to be open coded due to unusual existing escape mechanisms. [akpm@linux-foundation.org: add lost chunk, per Kees] [keescook@chromium.org: seq_show_option should be using const parameters] Signed-off-by: Kees Cook Acked-by: Serge Hallyn Acked-by: Jan Kara Acked-by: Paul Moore Cc: J. R. Okajima Signed-off-by: Kees Cook Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [ luis: backported to 3.16: - dropped changes to fs/overlayfs/super.c, net/ceph/ceph_common.c and to cgroup_show_options() in kernel/cgroup.c - adjusted context ] Signed-off-by: Luis Henriques Signed-off-by: Kamal Mostafa --- fs/ceph/super.c | 3 ++- fs/cifs/cifsfs.c | 6 +++--- fs/ext4/super.c | 4 ++-- fs/gfs2/super.c | 6 +++--- fs/hfs/super.c | 4 ++-- fs/hfsplus/options.c | 4 ++-- fs/hostfs/hostfs_kern.c | 2 +- fs/ocfs2/super.c | 4 ++-- fs/reiserfs/super.c | 8 +++++--- fs/xfs/xfs_super.c | 4 ++-- include/linux/seq_file.h | 35 +++++++++++++++++++++++++++++++++++ kernel/cgroup.c | 5 +++-- security/selinux/hooks.c | 2 +- 13 files changed, 63 insertions(+), 24 deletions(-) diff --git a/fs/ceph/super.c b/fs/ceph/super.c index 6a0951e..c495508 100644 --- a/fs/ceph/super.c +++ b/fs/ceph/super.c @@ -460,7 +460,8 @@ static int ceph_show_options(struct seq_file *m, struct dentry *root) if (fsopt->max_readdir_bytes != CEPH_MAX_READDIR_BYTES_DEFAULT) seq_printf(m, ",readdir_max_bytes=%d", fsopt->max_readdir_bytes); if (strcmp(fsopt->snapdir_name, CEPH_SNAPDIRNAME_DEFAULT)) - seq_printf(m, ",snapdirname=%s", fsopt->snapdir_name); + seq_show_option(m, "snapdirname", fsopt->snapdir_name); + return 0; } diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c index 7c6b73c..c90d4bd 100644 --- a/fs/cifs/cifsfs.c +++ b/fs/cifs/cifsfs.c @@ -390,17 +390,17 @@ cifs_show_options(struct seq_file *s, struct dentry *root) struct sockaddr *srcaddr; srcaddr = (struct sockaddr *)&tcon->ses->server->srcaddr; - seq_printf(s, ",vers=%s", tcon->ses->server->vals->version_string); + seq_show_option(s, "vers", tcon->ses->server->vals->version_string); cifs_show_security(s, tcon->ses); cifs_show_cache_flavor(s, cifs_sb); if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MULTIUSER) seq_printf(s, ",multiuser"); else if (tcon->ses->user_name) - seq_printf(s, ",username=%s", tcon->ses->user_name); + seq_show_option(s, "username", tcon->ses->user_name); if (tcon->ses->domainName) - seq_printf(s, ",domain=%s", tcon->ses->domainName); + seq_show_option(s, "domain", tcon->ses->domainName); if (srcaddr->sa_family != AF_UNSPEC) { struct sockaddr_in *saddr4; diff --git a/fs/ext4/super.c b/fs/ext4/super.c index a07af5b..c261beb 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1744,10 +1744,10 @@ static inline void ext4_show_quota_options(struct seq_file *seq, } if (sbi->s_qf_names[USRQUOTA]) - seq_printf(seq, ",usrjquota=%s", sbi->s_qf_names[USRQUOTA]); + seq_show_option(seq, "usrjquota", sbi->s_qf_names[USRQUOTA]); if (sbi->s_qf_names[GRPQUOTA]) - seq_printf(seq, ",grpjquota=%s", sbi->s_qf_names[GRPQUOTA]); + seq_show_option(seq, "grpjquota", sbi->s_qf_names[GRPQUOTA]); #endif } diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c index 35da5b1..b05f395 100644 --- a/fs/gfs2/super.c +++ b/fs/gfs2/super.c @@ -1258,11 +1258,11 @@ static int gfs2_show_options(struct seq_file *s, struct dentry *root) if (is_ancestor(root, sdp->sd_master_dir)) seq_printf(s, ",meta"); if (args->ar_lockproto[0]) - seq_printf(s, ",lockproto=%s", args->ar_lockproto); + seq_show_option(s, "lockproto", args->ar_lockproto); if (args->ar_locktable[0]) - seq_printf(s, ",locktable=%s", args->ar_locktable); + seq_show_option(s, "locktable", args->ar_locktable); if (args->ar_hostdata[0]) - seq_printf(s, ",hostdata=%s", args->ar_hostdata); + seq_show_option(s, "hostdata", args->ar_hostdata); if (args->ar_spectator) seq_printf(s, ",spectator"); if (args->ar_localflocks) diff --git a/fs/hfs/super.c b/fs/hfs/super.c index 2d2039e..52cd187 100644 --- a/fs/hfs/super.c +++ b/fs/hfs/super.c @@ -134,9 +134,9 @@ static int hfs_show_options(struct seq_file *seq, struct dentry *root) struct hfs_sb_info *sbi = HFS_SB(root->d_sb); if (sbi->s_creator != cpu_to_be32(0x3f3f3f3f)) - seq_printf(seq, ",creator=%.4s", (char *)&sbi->s_creator); + seq_show_option_n(seq, "creator", (char *)&sbi->s_creator, 4); if (sbi->s_type != cpu_to_be32(0x3f3f3f3f)) - seq_printf(seq, ",type=%.4s", (char *)&sbi->s_type); + seq_show_option_n(seq, "type", (char *)&sbi->s_type, 4); seq_printf(seq, ",uid=%u,gid=%u", from_kuid_munged(&init_user_ns, sbi->s_uid), from_kgid_munged(&init_user_ns, sbi->s_gid)); diff --git a/fs/hfsplus/options.c b/fs/hfsplus/options.c index 968eab5..beaae4e 100644 --- a/fs/hfsplus/options.c +++ b/fs/hfsplus/options.c @@ -219,9 +219,9 @@ int hfsplus_show_options(struct seq_file *seq, struct dentry *root) struct hfsplus_sb_info *sbi = HFSPLUS_SB(root->d_sb); if (sbi->creator != HFSPLUS_DEF_CR_TYPE) - seq_printf(seq, ",creator=%.4s", (char *)&sbi->creator); + seq_show_option_n(seq, "creator", (char *)&sbi->creator, 4); if (sbi->type != HFSPLUS_DEF_CR_TYPE) - seq_printf(seq, ",type=%.4s", (char *)&sbi->type); + seq_show_option_n(seq, "type", (char *)&sbi->type, 4); seq_printf(seq, ",umask=%o,uid=%u,gid=%u", sbi->umask, from_kuid_munged(&init_user_ns, sbi->uid), from_kgid_munged(&init_user_ns, sbi->gid)); diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c index db23ce1..5d2585a 100644 --- a/fs/hostfs/hostfs_kern.c +++ b/fs/hostfs/hostfs_kern.c @@ -255,7 +255,7 @@ static int hostfs_show_options(struct seq_file *seq, struct dentry *root) size_t offset = strlen(root_ino) + 1; if (strlen(root_path) > offset) - seq_printf(seq, ",%s", root_path + offset); + seq_show_option(seq, root_path + offset, NULL); return 0; } diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c index c414929..3e12b38 100644 --- a/fs/ocfs2/super.c +++ b/fs/ocfs2/super.c @@ -1578,8 +1578,8 @@ static int ocfs2_show_options(struct seq_file *s, struct dentry *root) seq_printf(s, ",localflocks,"); if (osb->osb_cluster_stack[0]) - seq_printf(s, ",cluster_stack=%.*s", OCFS2_STACK_LABEL_LEN, - osb->osb_cluster_stack); + seq_show_option_n(s, "cluster_stack", osb->osb_cluster_stack, + OCFS2_STACK_LABEL_LEN); if (opts & OCFS2_MOUNT_USRQUOTA) seq_printf(s, ",usrquota"); if (opts & OCFS2_MOUNT_GRPQUOTA) diff --git a/fs/reiserfs/super.c b/fs/reiserfs/super.c index 3ead145..b2506ca 100644 --- a/fs/reiserfs/super.c +++ b/fs/reiserfs/super.c @@ -690,18 +690,20 @@ static int reiserfs_show_options(struct seq_file *seq, struct dentry *root) seq_puts(seq, ",acl"); if (REISERFS_SB(s)->s_jdev) - seq_printf(seq, ",jdev=%s", REISERFS_SB(s)->s_jdev); + seq_show_option(seq, "jdev", REISERFS_SB(s)->s_jdev); if (journal->j_max_commit_age != journal->j_default_max_commit_age) seq_printf(seq, ",commit=%d", journal->j_max_commit_age); #ifdef CONFIG_QUOTA if (REISERFS_SB(s)->s_qf_names[USRQUOTA]) - seq_printf(seq, ",usrjquota=%s", REISERFS_SB(s)->s_qf_names[USRQUOTA]); + seq_show_option(seq, "usrjquota", + REISERFS_SB(s)->s_qf_names[USRQUOTA]); else if (opts & (1 << REISERFS_USRQUOTA)) seq_puts(seq, ",usrquota"); if (REISERFS_SB(s)->s_qf_names[GRPQUOTA]) - seq_printf(seq, ",grpjquota=%s", REISERFS_SB(s)->s_qf_names[GRPQUOTA]); + seq_show_option(seq, "grpjquota", + REISERFS_SB(s)->s_qf_names[GRPQUOTA]); else if (opts & (1 << REISERFS_GRPQUOTA)) seq_puts(seq, ",grpquota"); if (REISERFS_SB(s)->s_jquota_fmt) { diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c index d971f49..26d7693 100644 --- a/fs/xfs/xfs_super.c +++ b/fs/xfs/xfs_super.c @@ -529,9 +529,9 @@ xfs_showargs( seq_printf(m, "," MNTOPT_LOGBSIZE "=%dk", mp->m_logbsize >> 10); if (mp->m_logname) - seq_printf(m, "," MNTOPT_LOGDEV "=%s", mp->m_logname); + seq_show_option(m, MNTOPT_LOGDEV, mp->m_logname); if (mp->m_rtname) - seq_printf(m, "," MNTOPT_RTDEV "=%s", mp->m_rtname); + seq_show_option(m, MNTOPT_RTDEV, mp->m_rtname); if (mp->m_dalign > 0) seq_printf(m, "," MNTOPT_SUNIT "=%d", diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h index 52e0097..6288341 100644 --- a/include/linux/seq_file.h +++ b/include/linux/seq_file.h @@ -158,6 +158,41 @@ static inline struct user_namespace *seq_user_ns(struct seq_file *seq) #endif } +/** + * seq_show_options - display mount options with appropriate escapes. + * @m: the seq_file handle + * @name: the mount option name + * @value: the mount option name's value, can be NULL + */ +static inline void seq_show_option(struct seq_file *m, const char *name, + const char *value) +{ + seq_putc(m, ','); + seq_escape(m, name, ",= \t\n\\"); + if (value) { + seq_putc(m, '='); + seq_escape(m, value, ", \t\n\\"); + } +} + +/** + * seq_show_option_n - display mount options with appropriate escapes + * where @value must be a specific length. + * @m: the seq_file handle + * @name: the mount option name + * @value: the mount option name's value, cannot be NULL + * @length: the length of @value to display + * + * This is a macro since this uses "length" to define the size of the + * stack buffer. + */ +#define seq_show_option_n(m, name, value, length) { \ + char val_buf[length + 1]; \ + strncpy(val_buf, value, length); \ + val_buf[length] = '\0'; \ + seq_show_option(m, name, val_buf); \ +} + #define SEQ_START_TOKEN ((void *)1) /* * Helpers for iteration over list_head-s in seq_files diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 6f2aae9..c02e4d7 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1107,11 +1107,12 @@ static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry) if (root->flags & CGRP_ROOT_XATTR) seq_puts(seq, ",xattr"); if (strlen(root->release_agent_path)) - seq_printf(seq, ",release_agent=%s", root->release_agent_path); + seq_show_option(seq, "release_agent", + root->release_agent_path); if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags)) seq_puts(seq, ",clone_children"); if (strlen(root->name)) - seq_printf(seq, ",name=%s", root->name); + seq_show_option(seq, "name", root->name); mutex_unlock(&cgroup_root_mutex); return 0; } diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 3138402..3b38a36 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -1101,7 +1101,7 @@ static void selinux_write_opts(struct seq_file *m, seq_puts(m, prefix); if (has_comma) seq_putc(m, '\"'); - seq_puts(m, opts->mnt_opts[i]); + seq_escape(m, opts->mnt_opts[i], "\"\n\\"); if (has_comma) seq_putc(m, '\"'); }