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![Christian Brauner](/assets/img/avatar_default.png)
Multiple places open-code the same check to determine whether a given mount is idmapped. Introduce a simple helper function that can be used instead. This allows us to get rid of the fragile open-coding. We will later change the check that is used to determine whether a given mount is idmapped. Introducing a helper allows us to do this in a single place instead of doing it for multiple places. Link: https://lore.kernel.org/r/20211123114227.3124056-2-brauner@kernel.org (v1) Link: https://lore.kernel.org/r/20211130121032.3753852-2-brauner@kernel.org (v2) Link: https://lore.kernel.org/r/20211203111707.3901969-2-brauner@kernel.org Cc: Seth Forshee <sforshee@digitalocean.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Al Viro <viro@zeniv.linux.org.uk> CC: linux-fsdevel@vger.kernel.org Reviewed-by: Amir Goldstein <amir73il@gmail.com> Reviewed-by: Seth Forshee <sforshee@digitalocean.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
348 lines
8.1 KiB
C
348 lines
8.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* fs/proc_namespace.c - handling of /proc/<pid>/{mounts,mountinfo,mountstats}
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*
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* In fact, that's a piece of procfs; it's *almost* isolated from
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* the rest of fs/proc, but has rather close relationships with
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* fs/namespace.c, thus here instead of fs/proc
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*
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*/
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#include <linux/mnt_namespace.h>
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#include <linux/nsproxy.h>
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#include <linux/security.h>
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#include <linux/fs_struct.h>
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#include <linux/sched/task.h>
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#include "proc/internal.h" /* only for get_proc_task() in ->open() */
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#include "pnode.h"
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#include "internal.h"
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static __poll_t mounts_poll(struct file *file, poll_table *wait)
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{
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struct seq_file *m = file->private_data;
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struct proc_mounts *p = m->private;
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struct mnt_namespace *ns = p->ns;
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__poll_t res = EPOLLIN | EPOLLRDNORM;
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int event;
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poll_wait(file, &p->ns->poll, wait);
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event = READ_ONCE(ns->event);
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if (m->poll_event != event) {
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m->poll_event = event;
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res |= EPOLLERR | EPOLLPRI;
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}
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return res;
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}
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struct proc_fs_opts {
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int flag;
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const char *str;
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};
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static int show_sb_opts(struct seq_file *m, struct super_block *sb)
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{
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static const struct proc_fs_opts fs_opts[] = {
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{ SB_SYNCHRONOUS, ",sync" },
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{ SB_DIRSYNC, ",dirsync" },
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{ SB_MANDLOCK, ",mand" },
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{ SB_LAZYTIME, ",lazytime" },
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{ 0, NULL }
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};
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const struct proc_fs_opts *fs_infop;
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for (fs_infop = fs_opts; fs_infop->flag; fs_infop++) {
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if (sb->s_flags & fs_infop->flag)
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seq_puts(m, fs_infop->str);
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}
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return security_sb_show_options(m, sb);
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}
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static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
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{
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static const struct proc_fs_opts mnt_opts[] = {
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{ MNT_NOSUID, ",nosuid" },
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{ MNT_NODEV, ",nodev" },
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{ MNT_NOEXEC, ",noexec" },
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{ MNT_NOATIME, ",noatime" },
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{ MNT_NODIRATIME, ",nodiratime" },
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{ MNT_RELATIME, ",relatime" },
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{ MNT_NOSYMFOLLOW, ",nosymfollow" },
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{ 0, NULL }
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};
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const struct proc_fs_opts *fs_infop;
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for (fs_infop = mnt_opts; fs_infop->flag; fs_infop++) {
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if (mnt->mnt_flags & fs_infop->flag)
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seq_puts(m, fs_infop->str);
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}
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if (is_idmapped_mnt(mnt))
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seq_puts(m, ",idmapped");
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}
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static inline void mangle(struct seq_file *m, const char *s)
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{
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seq_escape(m, s, " \t\n\\");
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}
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static void show_type(struct seq_file *m, struct super_block *sb)
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{
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mangle(m, sb->s_type->name);
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if (sb->s_subtype) {
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seq_putc(m, '.');
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mangle(m, sb->s_subtype);
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}
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}
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static int show_vfsmnt(struct seq_file *m, struct vfsmount *mnt)
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{
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struct proc_mounts *p = m->private;
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struct mount *r = real_mount(mnt);
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struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
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struct super_block *sb = mnt_path.dentry->d_sb;
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int err;
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if (sb->s_op->show_devname) {
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err = sb->s_op->show_devname(m, mnt_path.dentry);
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if (err)
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goto out;
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} else {
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mangle(m, r->mnt_devname ? r->mnt_devname : "none");
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}
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seq_putc(m, ' ');
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/* mountpoints outside of chroot jail will give SEQ_SKIP on this */
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err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
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if (err)
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goto out;
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seq_putc(m, ' ');
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show_type(m, sb);
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seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
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err = show_sb_opts(m, sb);
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if (err)
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goto out;
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show_mnt_opts(m, mnt);
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if (sb->s_op->show_options)
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err = sb->s_op->show_options(m, mnt_path.dentry);
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seq_puts(m, " 0 0\n");
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out:
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return err;
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}
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static int show_mountinfo(struct seq_file *m, struct vfsmount *mnt)
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{
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struct proc_mounts *p = m->private;
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struct mount *r = real_mount(mnt);
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struct super_block *sb = mnt->mnt_sb;
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struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
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int err;
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seq_printf(m, "%i %i %u:%u ", r->mnt_id, r->mnt_parent->mnt_id,
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MAJOR(sb->s_dev), MINOR(sb->s_dev));
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if (sb->s_op->show_path) {
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err = sb->s_op->show_path(m, mnt->mnt_root);
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if (err)
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goto out;
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} else {
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seq_dentry(m, mnt->mnt_root, " \t\n\\");
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}
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seq_putc(m, ' ');
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/* mountpoints outside of chroot jail will give SEQ_SKIP on this */
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err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
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if (err)
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goto out;
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seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
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show_mnt_opts(m, mnt);
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/* Tagged fields ("foo:X" or "bar") */
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if (IS_MNT_SHARED(r))
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seq_printf(m, " shared:%i", r->mnt_group_id);
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if (IS_MNT_SLAVE(r)) {
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int master = r->mnt_master->mnt_group_id;
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int dom = get_dominating_id(r, &p->root);
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seq_printf(m, " master:%i", master);
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if (dom && dom != master)
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seq_printf(m, " propagate_from:%i", dom);
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}
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if (IS_MNT_UNBINDABLE(r))
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seq_puts(m, " unbindable");
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/* Filesystem specific data */
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seq_puts(m, " - ");
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show_type(m, sb);
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seq_putc(m, ' ');
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if (sb->s_op->show_devname) {
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err = sb->s_op->show_devname(m, mnt->mnt_root);
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if (err)
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goto out;
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} else {
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mangle(m, r->mnt_devname ? r->mnt_devname : "none");
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}
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seq_puts(m, sb_rdonly(sb) ? " ro" : " rw");
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err = show_sb_opts(m, sb);
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if (err)
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goto out;
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if (sb->s_op->show_options)
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err = sb->s_op->show_options(m, mnt->mnt_root);
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seq_putc(m, '\n');
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out:
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return err;
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}
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static int show_vfsstat(struct seq_file *m, struct vfsmount *mnt)
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{
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struct proc_mounts *p = m->private;
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struct mount *r = real_mount(mnt);
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struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
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struct super_block *sb = mnt_path.dentry->d_sb;
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int err;
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/* device */
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if (sb->s_op->show_devname) {
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seq_puts(m, "device ");
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err = sb->s_op->show_devname(m, mnt_path.dentry);
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if (err)
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goto out;
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} else {
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if (r->mnt_devname) {
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seq_puts(m, "device ");
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mangle(m, r->mnt_devname);
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} else
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seq_puts(m, "no device");
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}
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/* mount point */
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seq_puts(m, " mounted on ");
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/* mountpoints outside of chroot jail will give SEQ_SKIP on this */
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err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
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if (err)
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goto out;
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seq_putc(m, ' ');
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/* file system type */
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seq_puts(m, "with fstype ");
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show_type(m, sb);
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/* optional statistics */
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if (sb->s_op->show_stats) {
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seq_putc(m, ' ');
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err = sb->s_op->show_stats(m, mnt_path.dentry);
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}
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seq_putc(m, '\n');
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out:
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return err;
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}
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static int mounts_open_common(struct inode *inode, struct file *file,
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int (*show)(struct seq_file *, struct vfsmount *))
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{
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struct task_struct *task = get_proc_task(inode);
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struct nsproxy *nsp;
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struct mnt_namespace *ns = NULL;
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struct path root;
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struct proc_mounts *p;
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struct seq_file *m;
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int ret = -EINVAL;
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if (!task)
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goto err;
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task_lock(task);
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nsp = task->nsproxy;
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if (!nsp || !nsp->mnt_ns) {
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task_unlock(task);
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put_task_struct(task);
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goto err;
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}
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ns = nsp->mnt_ns;
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get_mnt_ns(ns);
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if (!task->fs) {
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task_unlock(task);
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put_task_struct(task);
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ret = -ENOENT;
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goto err_put_ns;
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}
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get_fs_root(task->fs, &root);
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task_unlock(task);
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put_task_struct(task);
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ret = seq_open_private(file, &mounts_op, sizeof(struct proc_mounts));
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if (ret)
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goto err_put_path;
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m = file->private_data;
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m->poll_event = ns->event;
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p = m->private;
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p->ns = ns;
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p->root = root;
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p->show = show;
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INIT_LIST_HEAD(&p->cursor.mnt_list);
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p->cursor.mnt.mnt_flags = MNT_CURSOR;
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return 0;
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err_put_path:
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path_put(&root);
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err_put_ns:
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put_mnt_ns(ns);
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err:
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return ret;
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}
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static int mounts_release(struct inode *inode, struct file *file)
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{
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struct seq_file *m = file->private_data;
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struct proc_mounts *p = m->private;
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path_put(&p->root);
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mnt_cursor_del(p->ns, &p->cursor);
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put_mnt_ns(p->ns);
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return seq_release_private(inode, file);
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}
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static int mounts_open(struct inode *inode, struct file *file)
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{
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return mounts_open_common(inode, file, show_vfsmnt);
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}
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static int mountinfo_open(struct inode *inode, struct file *file)
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{
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return mounts_open_common(inode, file, show_mountinfo);
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}
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static int mountstats_open(struct inode *inode, struct file *file)
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{
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return mounts_open_common(inode, file, show_vfsstat);
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}
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const struct file_operations proc_mounts_operations = {
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.open = mounts_open,
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.read_iter = seq_read_iter,
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.splice_read = generic_file_splice_read,
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.llseek = seq_lseek,
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.release = mounts_release,
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.poll = mounts_poll,
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};
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const struct file_operations proc_mountinfo_operations = {
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.open = mountinfo_open,
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.read_iter = seq_read_iter,
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.splice_read = generic_file_splice_read,
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.llseek = seq_lseek,
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.release = mounts_release,
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.poll = mounts_poll,
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};
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const struct file_operations proc_mountstats_operations = {
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.open = mountstats_open,
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.read_iter = seq_read_iter,
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.splice_read = generic_file_splice_read,
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.llseek = seq_lseek,
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.release = mounts_release,
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};
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