linux/fs/notify/fdinfo.c
Amir Goldstein 7cea2a3c50 fanotify: support limited functionality for unprivileged users
Add limited support for unprivileged fanotify groups.
An unprivileged users is not allowed to get an open file descriptor in
the event nor the process pid of another process.  An unprivileged user
cannot request permission events, cannot set mount/filesystem marks and
cannot request unlimited queue/marks.

This enables the limited functionality similar to inotify when watching a
set of files and directories for OPEN/ACCESS/MODIFY/CLOSE events, without
requiring SYS_CAP_ADMIN privileges.

The FAN_REPORT_DFID_NAME init flag, provide a method for an unprivileged
listener watching a set of directories (with FAN_EVENT_ON_CHILD) to monitor
all changes inside those directories.

This typically requires that the listener keeps a map of watched directory
fid to dirfd (O_PATH), where fid is obtained with name_to_handle_at()
before starting to watch for changes.

When getting an event, the reported fid of the parent should be resolved
to dirfd and fstatsat(2) with dirfd and name should be used to query the
state of the filesystem entry.

Link: https://lore.kernel.org/r/20210304112921.3996419-3-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
2021-03-16 16:55:05 +01:00

158 lines
4.2 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/fsnotify_backend.h>
#include <linux/idr.h>
#include <linux/init.h>
#include <linux/inotify.h>
#include <linux/fanotify.h>
#include <linux/kernel.h>
#include <linux/namei.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/seq_file.h>
#include <linux/exportfs.h>
#include "inotify/inotify.h"
#include "fdinfo.h"
#include "fsnotify.h"
#if defined(CONFIG_PROC_FS)
#if defined(CONFIG_INOTIFY_USER) || defined(CONFIG_FANOTIFY)
static void show_fdinfo(struct seq_file *m, struct file *f,
void (*show)(struct seq_file *m,
struct fsnotify_mark *mark))
{
struct fsnotify_group *group = f->private_data;
struct fsnotify_mark *mark;
mutex_lock(&group->mark_mutex);
list_for_each_entry(mark, &group->marks_list, g_list) {
show(m, mark);
if (seq_has_overflowed(m))
break;
}
mutex_unlock(&group->mark_mutex);
}
#if defined(CONFIG_EXPORTFS)
static void show_mark_fhandle(struct seq_file *m, struct inode *inode)
{
struct {
struct file_handle handle;
u8 pad[MAX_HANDLE_SZ];
} f;
int size, ret, i;
f.handle.handle_bytes = sizeof(f.pad);
size = f.handle.handle_bytes >> 2;
ret = exportfs_encode_inode_fh(inode, (struct fid *)f.handle.f_handle, &size, NULL);
if ((ret == FILEID_INVALID) || (ret < 0)) {
WARN_ONCE(1, "Can't encode file handler for inotify: %d\n", ret);
return;
}
f.handle.handle_type = ret;
f.handle.handle_bytes = size * sizeof(u32);
seq_printf(m, "fhandle-bytes:%x fhandle-type:%x f_handle:",
f.handle.handle_bytes, f.handle.handle_type);
for (i = 0; i < f.handle.handle_bytes; i++)
seq_printf(m, "%02x", (int)f.handle.f_handle[i]);
}
#else
static void show_mark_fhandle(struct seq_file *m, struct inode *inode)
{
}
#endif
#ifdef CONFIG_INOTIFY_USER
static void inotify_fdinfo(struct seq_file *m, struct fsnotify_mark *mark)
{
struct inotify_inode_mark *inode_mark;
struct inode *inode;
if (mark->connector->type != FSNOTIFY_OBJ_TYPE_INODE)
return;
inode_mark = container_of(mark, struct inotify_inode_mark, fsn_mark);
inode = igrab(fsnotify_conn_inode(mark->connector));
if (inode) {
/*
* IN_ALL_EVENTS represents all of the mask bits
* that we expose to userspace. There is at
* least one bit (FS_EVENT_ON_CHILD) which is
* used only internally to the kernel.
*/
u32 mask = mark->mask & IN_ALL_EVENTS;
seq_printf(m, "inotify wd:%x ino:%lx sdev:%x mask:%x ignored_mask:%x ",
inode_mark->wd, inode->i_ino, inode->i_sb->s_dev,
mask, mark->ignored_mask);
show_mark_fhandle(m, inode);
seq_putc(m, '\n');
iput(inode);
}
}
void inotify_show_fdinfo(struct seq_file *m, struct file *f)
{
show_fdinfo(m, f, inotify_fdinfo);
}
#endif /* CONFIG_INOTIFY_USER */
#ifdef CONFIG_FANOTIFY
static void fanotify_fdinfo(struct seq_file *m, struct fsnotify_mark *mark)
{
unsigned int mflags = 0;
struct inode *inode;
if (mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)
mflags |= FAN_MARK_IGNORED_SURV_MODIFY;
if (mark->connector->type == FSNOTIFY_OBJ_TYPE_INODE) {
inode = igrab(fsnotify_conn_inode(mark->connector));
if (!inode)
return;
seq_printf(m, "fanotify ino:%lx sdev:%x mflags:%x mask:%x ignored_mask:%x ",
inode->i_ino, inode->i_sb->s_dev,
mflags, mark->mask, mark->ignored_mask);
show_mark_fhandle(m, inode);
seq_putc(m, '\n');
iput(inode);
} else if (mark->connector->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT) {
struct mount *mnt = fsnotify_conn_mount(mark->connector);
seq_printf(m, "fanotify mnt_id:%x mflags:%x mask:%x ignored_mask:%x\n",
mnt->mnt_id, mflags, mark->mask, mark->ignored_mask);
} else if (mark->connector->type == FSNOTIFY_OBJ_TYPE_SB) {
struct super_block *sb = fsnotify_conn_sb(mark->connector);
seq_printf(m, "fanotify sdev:%x mflags:%x mask:%x ignored_mask:%x\n",
sb->s_dev, mflags, mark->mask, mark->ignored_mask);
}
}
void fanotify_show_fdinfo(struct seq_file *m, struct file *f)
{
struct fsnotify_group *group = f->private_data;
seq_printf(m, "fanotify flags:%x event-flags:%x\n",
group->fanotify_data.flags,
group->fanotify_data.f_flags);
show_fdinfo(m, f, fanotify_fdinfo);
}
#endif /* CONFIG_FANOTIFY */
#endif /* CONFIG_INOTIFY_USER || CONFIG_FANOTIFY */
#endif /* CONFIG_PROC_FS */