From d3b428f0361d6dcbe7c6665ae0a824517a0b1ca9 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 4 Sep 2015 15:44:57 -0700 Subject: [PATCH] fs: create and use seq_show_option for escaping 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 Signed-off-by: Greg Kroah-Hartman --- fs/ceph/super.c | 2 +- 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/overlayfs/super.c | 6 +++--- fs/reiserfs/super.c | 8 +++++--- fs/xfs/xfs_super.c | 4 ++-- include/linux/seq_file.h | 35 +++++++++++++++++++++++++++++++++++ kernel/cgroup.c | 7 ++++--- net/ceph/ceph_common.c | 7 +++++-- security/selinux/hooks.c | 2 +- 15 files changed, 71 insertions(+), 30 deletions(-) diff --git a/fs/ceph/super.c b/fs/ceph/super.c index 4e9905374078a..0d47422e35481 100644 --- a/fs/ceph/super.c +++ b/fs/ceph/super.c @@ -466,7 +466,7 @@ 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 0a9fb6b53126a..6a1119e87fbb6 100644 --- a/fs/cifs/cifsfs.c +++ b/fs/cifs/cifsfs.c @@ -394,17 +394,17 @@ 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_puts(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 ca12affdba961..6b4eb94b04a59 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1738,10 +1738,10 @@ 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 859c6edbf81a0..c18b49dc5d4f6 100644 --- a/fs/gfs2/super.c +++ b/fs/gfs2/super.c @@ -1334,11 +1334,11 @@ static int gfs2_show_options(struct seq_file *s, struct dentry *root) if (is_ancestor(root, sdp->sd_master_dir)) seq_puts(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_puts(s, ",spectator"); if (args->ar_localflocks) diff --git a/fs/hfs/super.c b/fs/hfs/super.c index eee7206c38d18..410b65eea683d 100644 --- a/fs/hfs/super.c +++ b/fs/hfs/super.c @@ -135,9 +135,9 @@ 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 c90b72ee676d8..bb806e58c9770 100644 --- a/fs/hfsplus/options.c +++ b/fs/hfsplus/options.c @@ -218,9 +218,9 @@ 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 07d8d8f52faf5..de2d6245e9fad 100644 --- a/fs/hostfs/hostfs_kern.c +++ b/fs/hostfs/hostfs_kern.c @@ -260,7 +260,7 @@ 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); if (append) seq_puts(seq, ",append"); diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c index 403c5660b3064..a482e312c7b28 100644 --- a/fs/ocfs2/super.c +++ b/fs/ocfs2/super.c @@ -1550,8 +1550,8 @@ 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/overlayfs/super.c b/fs/overlayfs/super.c index bf8537c7f4552..155989455a721 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -517,10 +517,10 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry) struct super_block *sb = dentry->d_sb; struct ovl_fs *ufs = sb->s_fs_info; - seq_printf(m, ",lowerdir=%s", ufs->config.lowerdir); + seq_show_option(m, "lowerdir", ufs->config.lowerdir); if (ufs->config.upperdir) { - seq_printf(m, ",upperdir=%s", ufs->config.upperdir); - seq_printf(m, ",workdir=%s", ufs->config.workdir); + seq_show_option(m, "upperdir", ufs->config.upperdir); + seq_show_option(m, "workdir", ufs->config.workdir); } return 0; } diff --git a/fs/reiserfs/super.c b/fs/reiserfs/super.c index 0111ad0466ed4..cf6fa25f884b4 100644 --- a/fs/reiserfs/super.c +++ b/fs/reiserfs/super.c @@ -714,18 +714,20 @@ 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 858e1e62bbaa3..65a45372fb1f3 100644 --- a/fs/xfs/xfs_super.c +++ b/fs/xfs/xfs_super.c @@ -504,9 +504,9 @@ 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 afbb1fd77c772..7848473a5bc8b 100644 --- a/include/linux/seq_file.h +++ b/include/linux/seq_file.h @@ -148,6 +148,41 @@ 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 e8a5491be756a..4d65b66ae60d4 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1319,7 +1319,7 @@ static int cgroup_show_options(struct seq_file *seq, for_each_subsys(ss, ssid) if (root->subsys_mask & (1 << ssid)) - seq_printf(seq, ",%s", ss->name); + seq_show_option(seq, ss->name, NULL); if (root->flags & CGRP_ROOT_NOPREFIX) seq_puts(seq, ",noprefix"); if (root->flags & CGRP_ROOT_XATTR) @@ -1327,13 +1327,14 @@ static int cgroup_show_options(struct seq_file *seq, spin_lock(&release_agent_path_lock); 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); spin_unlock(&release_agent_path_lock); if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags)) seq_puts(seq, ",clone_children"); if (strlen(root->name)) - seq_printf(seq, ",name=%s", root->name); + seq_show_option(seq, "name", root->name); return 0; } diff --git a/net/ceph/ceph_common.c b/net/ceph/ceph_common.c index 79e8f71aef5be..3f76eb84b395f 100644 --- a/net/ceph/ceph_common.c +++ b/net/ceph/ceph_common.c @@ -495,8 +495,11 @@ int ceph_print_client_options(struct seq_file *m, struct ceph_client *client) struct ceph_options *opt = client->options; size_t pos = m->count; - if (opt->name) - seq_printf(m, "name=%s,", opt->name); + if (opt->name) { + seq_puts(m, "name="); + seq_escape(m, opt->name, ", \t\n\\"); + seq_putc(m, ','); + } if (opt->key) seq_puts(m, "secret=,"); diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 7f8d7f19e0446..280235cc3a980 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -1095,7 +1095,7 @@ 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, '\"'); }