From: Miklos Szeredi 1. Only show reachable mounts in /proc//mountinfo, this makes mountpoints unambiguous for chrooted processes. 2. Instead of showing mountpoints relative to the current root, always show them relative to the queried task's root. This means, that a particular mountinfo file will always have the same contents, regardless of which process is reading the file. Which is a lot more consistent, than the current behavior of /proc//mounts. Addressed comments from Jan Blunck and Ram Pai. Signed-off-by: Miklos Szeredi --- fs/dcache.c | 16 ++++++--- fs/namespace.c | 23 +++++++++----- fs/pnode.c | 28 ++++++++++++++--- fs/pnode.h | 2 - fs/proc/base.c | 68 ++++++++++++++++++++++++++---------------- fs/seq_file.c | 25 +++++++++++++++ include/linux/dcache.h | 1 include/linux/mnt_namespace.h | 8 ++++ include/linux/seq_file.h | 2 + 9 files changed, 128 insertions(+), 45 deletions(-) Index: linux/fs/dcache.c =================================================================== --- linux.orig/fs/dcache.c 2008-03-13 20:45:52.000000000 +0100 +++ linux/fs/dcache.c 2008-03-13 20:45:53.000000000 +0100 @@ -1760,12 +1760,12 @@ static int prepend(char **buffer, int *b /** * d_path - return the path of a dentry - * @dentry: dentry to report - * @vfsmnt: vfsmnt to which the dentry belongs + * @path: the dentry/vfsmount to report * @root: root dentry * @rootmnt: vfsmnt to which the root dentry belongs * @buffer: buffer to return value in * @buflen: buffer length + * @only_reachable: if true, then path must be reachable from root * * Convert a dentry into an ASCII path name. If the entry has been deleted * the string " (deleted)" is appended. Note that this is ambiguous. @@ -1774,9 +1774,11 @@ static int prepend(char **buffer, int *b * * "buflen" should be positive. Caller holds the dcache_lock. */ -static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt, - struct path *root, char *buffer, int buflen) +char *__d_path(struct path *path, struct path *root, char *buffer, int buflen, + bool only_reachable) { + struct dentry *dentry = path->dentry; + struct vfsmount *vfsmnt = path->mnt; char * end = buffer+buflen; char * retval; @@ -1821,6 +1823,8 @@ static char *__d_path(struct dentry *den return retval; global_root: + if (only_reachable) + return ERR_PTR(-EINVAL); retval += 1; /* hit the slash */ if (prepend(&retval, &buflen, dentry->d_name.name, dentry->d_name.len) != 0) @@ -1863,7 +1867,7 @@ char *d_path(struct path *path, char *bu path_get(¤t->fs->root); read_unlock(¤t->fs->lock); spin_lock(&dcache_lock); - res = __d_path(path->dentry, path->mnt, &root, buf, buflen); + res = __d_path(path, &root, buf, buflen, false); spin_unlock(&dcache_lock); path_put(&root); return res; @@ -1976,7 +1980,7 @@ asmlinkage long sys_getcwd(char __user * unsigned long len; char * cwd; - cwd = __d_path(pwd.dentry, pwd.mnt, &root, page, PAGE_SIZE); + cwd = __d_path(&pwd, &root, page, PAGE_SIZE, false); spin_unlock(&dcache_lock); error = PTR_ERR(cwd); Index: linux/fs/namespace.c =================================================================== --- linux.orig/fs/namespace.c 2008-03-13 20:45:52.000000000 +0100 +++ linux/fs/namespace.c 2008-03-13 20:45:53.000000000 +0100 @@ -683,17 +683,17 @@ EXPORT_SYMBOL(save_mount_options); /* iterator */ static void *m_start(struct seq_file *m, loff_t *pos) { - struct mnt_namespace *n = m->private; + struct proc_mounts *p = m->private; down_read(&namespace_sem); - return seq_list_start(&n->list, *pos); + return seq_list_start(&p->ns->list, *pos); } static void *m_next(struct seq_file *m, void *v, loff_t *pos) { - struct mnt_namespace *n = m->private; + struct proc_mounts *p = m->private; - return seq_list_next(v, &n->list, pos); + return seq_list_next(v, &p->ns->list, pos); } static void m_stop(struct seq_file *m, void *v) @@ -779,6 +779,8 @@ const struct seq_operations mounts_op = static int show_mountinfo(struct seq_file *m, void *v) { + struct proc_mounts *p = m->private; + size_t count_save = m->count; struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); struct super_block *sb = mnt->mnt_sb; struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; @@ -792,7 +794,11 @@ static int show_mountinfo(struct seq_fil seq_putc(m, ' '); seq_dentry(m, mnt->mnt_root, " \t\n\\"); seq_putc(m, ' '); - seq_path(m, &mnt_path, " \t\n\\"); + if (seq_path_root(m, &mnt_path, &p->root, " \t\n\\") == -EINVAL) { + /* path is outside root */ + m->count = count_save; + return 0; + } seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw"); show_mnt_opts(m, mnt); seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw"); @@ -804,14 +810,15 @@ static int show_mountinfo(struct seq_fil if (IS_MNT_SHARED(mnt)) seq_printf(m, "shared:%i", get_peer_group_id(mnt)); if (IS_MNT_SLAVE(mnt)) { - int dominator_id = get_dominator_id_same_ns(mnt); + int dominator; if (IS_MNT_SHARED(mnt)) seq_putc(m, ','); seq_printf(m, "slave:%i", get_master_group_id(mnt)); - if (dominator_id != -1) - seq_printf(m, ":%i", dominator_id); + dominator = get_dominator_id_same_root(mnt, &p->root); + if (dominator != -1) + seq_printf(m, ":%i", dominator); } } else if (IS_MNT_UNBINDABLE(mnt)) { seq_printf(m, "unbindable"); Index: linux/fs/proc/base.c =================================================================== --- linux.orig/fs/proc/base.c 2008-03-13 20:45:15.000000000 +0100 +++ linux/fs/proc/base.c 2008-03-13 20:45:53.000000000 +0100 @@ -502,17 +502,14 @@ static const struct inode_operations pro .setattr = proc_setattr, }; -struct proc_mounts { - struct seq_file m; - int event; -}; - static int mounts_open_common(struct inode *inode, struct file *file, const struct seq_operations *op) { struct task_struct *task = get_proc_task(inode); struct nsproxy *nsp; struct mnt_namespace *ns = NULL; + struct fs_struct *fs = NULL; + struct path root; struct proc_mounts *p; int ret = -EINVAL; @@ -525,40 +522,61 @@ static int mounts_open_common(struct ino get_mnt_ns(ns); } rcu_read_unlock(); - + if (ns) + fs = get_fs_struct(task); put_task_struct(task); } - if (ns) { - ret = -ENOMEM; - p = kmalloc(sizeof(struct proc_mounts), GFP_KERNEL); - if (p) { - file->private_data = &p->m; - ret = seq_open(file, op); - if (!ret) { - p->m.private = ns; - p->event = ns->event; - return 0; - } - kfree(p); - } - put_mnt_ns(ns); - } + if (!ns) + goto err; + if (!fs) + goto err_put_ns; + + read_lock(&fs->lock); + root = fs->root; + path_get(&root); + read_unlock(&fs->lock); + put_fs_struct(fs); + + ret = -ENOMEM; + p = kmalloc(sizeof(struct proc_mounts), GFP_KERNEL); + if (!p) + goto err_put_path; + + file->private_data = &p->m; + ret = seq_open(file, op); + if (ret) + goto err_free; + + p->m.private = p; + p->ns = ns; + p->root = root; + p->event = ns->event; + + return 0; + + err_free: + kfree(p); + err_put_path: + path_put(&root); + err_put_ns: + put_mnt_ns(ns); + err: return ret; } static int mounts_release(struct inode *inode, struct file *file) { - struct seq_file *m = file->private_data; - struct mnt_namespace *ns = m->private; - put_mnt_ns(ns); + struct proc_mounts *p = file->private_data; + path_put(&p->root); + put_mnt_ns(p->ns); return seq_release(inode, file); } static unsigned mounts_poll(struct file *file, poll_table *wait) { struct proc_mounts *p = file->private_data; - struct mnt_namespace *ns = p->m.private; + struct mnt_namespace *ns = p->ns; unsigned res = 0; poll_wait(file, &ns->poll, wait); Index: linux/fs/seq_file.c =================================================================== --- linux.orig/fs/seq_file.c 2008-03-13 20:45:52.000000000 +0100 +++ linux/fs/seq_file.c 2008-03-13 20:45:53.000000000 +0100 @@ -392,6 +392,31 @@ int seq_path(struct seq_file *m, struct EXPORT_SYMBOL(seq_path); #ifdef CONFIG_PROC_FS +int seq_path_root(struct seq_file *m, struct path *path, struct path *root, + char *esc) +{ + int err = -ENAMETOOLONG; + if (m->count < m->size) { + char *s = m->buf + m->count; + char *p; + + spin_lock(&dcache_lock); + p = __d_path(path, root, s, m->size - m->count, true); + spin_unlock(&dcache_lock); + err = PTR_ERR(p); + if (!IS_ERR(p)) { + s = mangle_path(s, p, esc); + if (s) { + p = m->buf + m->count; + m->count = s - m->buf; + return 0; + } + } + } + m->count = m->size; + return err; +} + /* * returns the path of the 'dentry' from the root of its filesystem. */ Index: linux/include/linux/dcache.h =================================================================== --- linux.orig/include/linux/dcache.h 2008-03-13 20:45:52.000000000 +0100 +++ linux/include/linux/dcache.h 2008-03-13 20:45:53.000000000 +0100 @@ -302,6 +302,7 @@ extern int d_validate(struct dentry *, s */ extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...); +extern char *__d_path(struct path *path, struct path *root, char *, int, bool); extern char *d_path(struct path *, char *, int); #ifdef CONFIG_PROC_FS Index: linux/include/linux/mnt_namespace.h =================================================================== --- linux.orig/include/linux/mnt_namespace.h 2008-03-13 20:45:15.000000000 +0100 +++ linux/include/linux/mnt_namespace.h 2008-03-13 20:45:53.000000000 +0100 @@ -5,6 +5,7 @@ #include #include #include +#include struct mnt_namespace { atomic_t count; @@ -14,6 +15,13 @@ struct mnt_namespace { int event; }; +struct proc_mounts { + struct seq_file m; /* must be the first element */ + struct mnt_namespace *ns; + struct path root; + int event; +}; + extern struct mnt_namespace *copy_mnt_ns(unsigned long, struct mnt_namespace *, struct fs_struct *); extern void __put_mnt_ns(struct mnt_namespace *ns); Index: linux/include/linux/seq_file.h =================================================================== --- linux.orig/include/linux/seq_file.h 2008-03-13 20:45:52.000000000 +0100 +++ linux/include/linux/seq_file.h 2008-03-13 20:45:53.000000000 +0100 @@ -46,6 +46,8 @@ int seq_printf(struct seq_file *, const int seq_path(struct seq_file *, struct path *, char *); #ifdef CONFIG_PROC_FS +int seq_path_root(struct seq_file *m, struct path *path, struct path *root, + char *esc); int seq_dentry(struct seq_file *, struct dentry *, char *); #endif /* CONFIG_PROC_FS */ Index: linux/fs/pnode.c =================================================================== --- linux.orig/fs/pnode.c 2008-03-13 20:45:52.000000000 +0100 +++ linux/fs/pnode.c 2008-03-13 20:45:53.000000000 +0100 @@ -89,28 +89,46 @@ int get_master_group_id(struct vfsmount return id; } -static struct vfsmount *get_peer_in_ns(struct vfsmount *mnt, - struct mnt_namespace *ns) +/* + * Return true if path is reachable from root + * + * Caller must hold vfsmount_lock + */ +static bool is_path_reachable(struct vfsmount *mnt, struct dentry *dentry, + const struct path *root) +{ + while (mnt != root->mnt && mnt->mnt_parent != mnt) { + dentry = mnt->mnt_mountpoint; + mnt = mnt->mnt_parent; + } + return mnt == root->mnt && is_subdir(dentry, root->dentry); +} + +static struct vfsmount *get_peer_under_root(struct vfsmount *mnt, + struct mnt_namespace *ns, + const struct path *root) { struct vfsmount *m = mnt; do { - if (m->mnt_ns == ns) + /* Check the namespace first for optimization */ + if (m->mnt_ns == ns && is_path_reachable(m, m->mnt_root, root)) return m; + m = next_peer(m); } while (m != mnt); return NULL; } -int get_dominator_id_same_ns(struct vfsmount *mnt) +int get_dominator_id_same_root(struct vfsmount *mnt, const struct path *root) { int id = -1; struct vfsmount *m; spin_lock(&vfsmount_lock); for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) { - struct vfsmount *d = get_peer_in_ns(m, mnt->mnt_ns); + struct vfsmount *d = get_peer_under_root(m, mnt->mnt_ns, root); if (d) { id = d->mnt_pgid; break; Index: linux/fs/pnode.h =================================================================== --- linux.orig/fs/pnode.h 2008-03-13 20:45:52.000000000 +0100 +++ linux/fs/pnode.h 2008-03-13 20:45:53.000000000 +0100 @@ -34,6 +34,6 @@ int propagate_mount_busy(struct vfsmount int get_peer_group_id(struct vfsmount *); int get_master_group_id(struct vfsmount *); -int get_dominator_id_same_ns(struct vfsmount *); +int get_dominator_id_same_root(struct vfsmount *, const struct path *); #endif /* _LINUX_PNODE_H */ -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/