linux-stable/fs/notify/fanotify/fanotify.c
Linus Torvalds 07c8f3bfef \n
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Merge tag 'fsnotify_for_v5.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

Pull fsnotify updates from Jan Kara:
 "Several smaller fixes and cleanups for fsnotify subsystem"

* tag 'fsnotify_for_v5.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  fanotify: fix ignore mask logic for events on child and on dir
  fanotify: don't write with size under sizeof(response)
  fsnotify: Remove proc_fs.h include
  fanotify: remove reference to fill_event_metadata()
  fsnotify: add mutex destroy
  fanotify: prefix should_merge()
  fanotify: Replace zero-length array with flexible-array
  inotify: Fix error return code assignment flow.
  fsnotify: Add missing annotation for fsnotify_finish_user_wait() and for fsnotify_prepare_user_wait()
2020-06-04 13:51:54 -07:00

658 lines
18 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <linux/fanotify.h>
#include <linux/fdtable.h>
#include <linux/fsnotify_backend.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/kernel.h> /* UINT_MAX */
#include <linux/mount.h>
#include <linux/sched.h>
#include <linux/sched/user.h>
#include <linux/sched/signal.h>
#include <linux/types.h>
#include <linux/wait.h>
#include <linux/audit.h>
#include <linux/sched/mm.h>
#include <linux/statfs.h>
#include "fanotify.h"
static bool fanotify_path_equal(struct path *p1, struct path *p2)
{
return p1->mnt == p2->mnt && p1->dentry == p2->dentry;
}
static inline bool fanotify_fsid_equal(__kernel_fsid_t *fsid1,
__kernel_fsid_t *fsid2)
{
return fsid1->val[0] == fsid2->val[0] && fsid1->val[1] == fsid2->val[1];
}
static bool fanotify_fh_equal(struct fanotify_fh *fh1,
struct fanotify_fh *fh2)
{
if (fh1->type != fh2->type || fh1->len != fh2->len)
return false;
/* Do not merge events if we failed to encode fh */
if (fh1->type == FILEID_INVALID)
return false;
return !fh1->len ||
!memcmp(fanotify_fh_buf(fh1), fanotify_fh_buf(fh2), fh1->len);
}
static bool fanotify_fid_event_equal(struct fanotify_fid_event *ffe1,
struct fanotify_fid_event *ffe2)
{
/* Do not merge fid events without object fh */
if (!ffe1->object_fh.len)
return false;
return fanotify_fsid_equal(&ffe1->fsid, &ffe2->fsid) &&
fanotify_fh_equal(&ffe1->object_fh, &ffe2->object_fh);
}
static bool fanotify_name_event_equal(struct fanotify_name_event *fne1,
struct fanotify_name_event *fne2)
{
/*
* Do not merge name events without dir fh.
* FAN_DIR_MODIFY does not encode object fh, so it may be empty.
*/
if (!fne1->dir_fh.len)
return false;
if (fne1->name_len != fne2->name_len ||
!fanotify_fh_equal(&fne1->dir_fh, &fne2->dir_fh))
return false;
return !memcmp(fne1->name, fne2->name, fne1->name_len);
}
static bool fanotify_should_merge(struct fsnotify_event *old_fsn,
struct fsnotify_event *new_fsn)
{
struct fanotify_event *old, *new;
pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn);
old = FANOTIFY_E(old_fsn);
new = FANOTIFY_E(new_fsn);
if (old_fsn->objectid != new_fsn->objectid ||
old->type != new->type || old->pid != new->pid)
return false;
switch (old->type) {
case FANOTIFY_EVENT_TYPE_PATH:
return fanotify_path_equal(fanotify_event_path(old),
fanotify_event_path(new));
case FANOTIFY_EVENT_TYPE_FID:
/*
* We want to merge many dirent events in the same dir (i.e.
* creates/unlinks/renames), but we do not want to merge dirent
* events referring to subdirs with dirent events referring to
* non subdirs, otherwise, user won't be able to tell from a
* mask FAN_CREATE|FAN_DELETE|FAN_ONDIR if it describes mkdir+
* unlink pair or rmdir+create pair of events.
*/
if ((old->mask & FS_ISDIR) != (new->mask & FS_ISDIR))
return false;
return fanotify_fid_event_equal(FANOTIFY_FE(old),
FANOTIFY_FE(new));
case FANOTIFY_EVENT_TYPE_FID_NAME:
return fanotify_name_event_equal(FANOTIFY_NE(old),
FANOTIFY_NE(new));
default:
WARN_ON_ONCE(1);
}
return false;
}
/* and the list better be locked by something too! */
static int fanotify_merge(struct list_head *list, struct fsnotify_event *event)
{
struct fsnotify_event *test_event;
struct fanotify_event *new;
pr_debug("%s: list=%p event=%p\n", __func__, list, event);
new = FANOTIFY_E(event);
/*
* Don't merge a permission event with any other event so that we know
* the event structure we have created in fanotify_handle_event() is the
* one we should check for permission response.
*/
if (fanotify_is_perm_event(new->mask))
return 0;
list_for_each_entry_reverse(test_event, list, list) {
if (fanotify_should_merge(test_event, event)) {
FANOTIFY_E(test_event)->mask |= new->mask;
return 1;
}
}
return 0;
}
/*
* Wait for response to permission event. The function also takes care of
* freeing the permission event (or offloads that in case the wait is canceled
* by a signal). The function returns 0 in case access got allowed by userspace,
* -EPERM in case userspace disallowed the access, and -ERESTARTSYS in case
* the wait got interrupted by a signal.
*/
static int fanotify_get_response(struct fsnotify_group *group,
struct fanotify_perm_event *event,
struct fsnotify_iter_info *iter_info)
{
int ret;
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
ret = wait_event_killable(group->fanotify_data.access_waitq,
event->state == FAN_EVENT_ANSWERED);
/* Signal pending? */
if (ret < 0) {
spin_lock(&group->notification_lock);
/* Event reported to userspace and no answer yet? */
if (event->state == FAN_EVENT_REPORTED) {
/* Event will get freed once userspace answers to it */
event->state = FAN_EVENT_CANCELED;
spin_unlock(&group->notification_lock);
return ret;
}
/* Event not yet reported? Just remove it. */
if (event->state == FAN_EVENT_INIT)
fsnotify_remove_queued_event(group, &event->fae.fse);
/*
* Event may be also answered in case signal delivery raced
* with wakeup. In that case we have nothing to do besides
* freeing the event and reporting error.
*/
spin_unlock(&group->notification_lock);
goto out;
}
/* userspace responded, convert to something usable */
switch (event->response & ~FAN_AUDIT) {
case FAN_ALLOW:
ret = 0;
break;
case FAN_DENY:
default:
ret = -EPERM;
}
/* Check if the response should be audited */
if (event->response & FAN_AUDIT)
audit_fanotify(event->response & ~FAN_AUDIT);
pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
group, event, ret);
out:
fsnotify_destroy_event(group, &event->fae.fse);
return ret;
}
/*
* This function returns a mask for an event that only contains the flags
* that have been specifically requested by the user. Flags that may have
* been included within the event mask, but have not been explicitly
* requested by the user, will not be present in the returned mask.
*/
static u32 fanotify_group_event_mask(struct fsnotify_group *group,
struct fsnotify_iter_info *iter_info,
u32 event_mask, const void *data,
int data_type)
{
__u32 marks_mask = 0, marks_ignored_mask = 0;
__u32 test_mask, user_mask = FANOTIFY_OUTGOING_EVENTS;
const struct path *path = fsnotify_data_path(data, data_type);
struct fsnotify_mark *mark;
int type;
pr_debug("%s: report_mask=%x mask=%x data=%p data_type=%d\n",
__func__, iter_info->report_mask, event_mask, data, data_type);
if (!FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
/* Do we have path to open a file descriptor? */
if (!path)
return 0;
/* Path type events are only relevant for files and dirs */
if (!d_is_reg(path->dentry) && !d_can_lookup(path->dentry))
return 0;
}
fsnotify_foreach_obj_type(type) {
if (!fsnotify_iter_should_report_type(iter_info, type))
continue;
mark = iter_info->marks[type];
/* Apply ignore mask regardless of ISDIR and ON_CHILD flags */
marks_ignored_mask |= mark->ignored_mask;
/*
* If the event is on dir and this mark doesn't care about
* events on dir, don't send it!
*/
if (event_mask & FS_ISDIR && !(mark->mask & FS_ISDIR))
continue;
/*
* If the event is for a child and this mark doesn't care about
* events on a child, don't send it!
*/
if (event_mask & FS_EVENT_ON_CHILD &&
(type != FSNOTIFY_OBJ_TYPE_INODE ||
!(mark->mask & FS_EVENT_ON_CHILD)))
continue;
marks_mask |= mark->mask;
}
test_mask = event_mask & marks_mask & ~marks_ignored_mask;
/*
* For dirent modification events (create/delete/move) that do not carry
* the child entry name information, we report FAN_ONDIR for mkdir/rmdir
* so user can differentiate them from creat/unlink.
*
* For backward compatibility and consistency, do not report FAN_ONDIR
* to user in legacy fanotify mode (reporting fd) and report FAN_ONDIR
* to user in FAN_REPORT_FID mode for all event types.
*/
if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
/* Do not report FAN_ONDIR without any event */
if (!(test_mask & ~FAN_ONDIR))
return 0;
} else {
user_mask &= ~FAN_ONDIR;
}
return test_mask & user_mask;
}
static void fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
gfp_t gfp)
{
int dwords, type, bytes = 0;
char *ext_buf = NULL;
void *buf = fh->buf;
int err;
if (!inode)
goto out;
dwords = 0;
err = -ENOENT;
type = exportfs_encode_inode_fh(inode, NULL, &dwords, NULL);
if (!dwords)
goto out_err;
bytes = dwords << 2;
if (bytes > FANOTIFY_INLINE_FH_LEN) {
/* Treat failure to allocate fh as failure to allocate event */
err = -ENOMEM;
ext_buf = kmalloc(bytes, gfp);
if (!ext_buf)
goto out_err;
*fanotify_fh_ext_buf_ptr(fh) = ext_buf;
buf = ext_buf;
}
type = exportfs_encode_inode_fh(inode, buf, &dwords, NULL);
err = -EINVAL;
if (!type || type == FILEID_INVALID || bytes != dwords << 2)
goto out_err;
fh->type = type;
fh->len = bytes;
return;
out_err:
pr_warn_ratelimited("fanotify: failed to encode fid (type=%d, len=%d, err=%i)\n",
type, bytes, err);
kfree(ext_buf);
*fanotify_fh_ext_buf_ptr(fh) = NULL;
out:
/* Report the event without a file identifier on encode error */
fh->type = FILEID_INVALID;
fh->len = 0;
}
/*
* The inode to use as identifier when reporting fid depends on the event.
* Report the modified directory inode on dirent modification events.
* Report the "victim" inode otherwise.
* For example:
* FS_ATTRIB reports the child inode even if reported on a watched parent.
* FS_CREATE reports the modified dir inode and not the created inode.
*/
static struct inode *fanotify_fid_inode(struct inode *to_tell, u32 event_mask,
const void *data, int data_type)
{
if (event_mask & ALL_FSNOTIFY_DIRENT_EVENTS)
return to_tell;
return (struct inode *)fsnotify_data_inode(data, data_type);
}
struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
struct inode *inode, u32 mask,
const void *data, int data_type,
const struct qstr *file_name,
__kernel_fsid_t *fsid)
{
struct fanotify_event *event = NULL;
struct fanotify_fid_event *ffe = NULL;
struct fanotify_name_event *fne = NULL;
gfp_t gfp = GFP_KERNEL_ACCOUNT;
struct inode *id = fanotify_fid_inode(inode, mask, data, data_type);
const struct path *path = fsnotify_data_path(data, data_type);
/*
* For queues with unlimited length lost events are not expected and
* can possibly have security implications. Avoid losing events when
* memory is short. For the limited size queues, avoid OOM killer in the
* target monitoring memcg as it may have security repercussion.
*/
if (group->max_events == UINT_MAX)
gfp |= __GFP_NOFAIL;
else
gfp |= __GFP_RETRY_MAYFAIL;
/* Whoever is interested in the event, pays for the allocation. */
memalloc_use_memcg(group->memcg);
if (fanotify_is_perm_event(mask)) {
struct fanotify_perm_event *pevent;
pevent = kmem_cache_alloc(fanotify_perm_event_cachep, gfp);
if (!pevent)
goto out;
event = &pevent->fae;
event->type = FANOTIFY_EVENT_TYPE_PATH_PERM;
pevent->response = 0;
pevent->state = FAN_EVENT_INIT;
goto init;
}
/*
* For FAN_DIR_MODIFY event, we report the fid of the directory and
* the name of the modified entry.
* Allocate an fanotify_name_event struct and copy the name.
*/
if (mask & FAN_DIR_MODIFY && !(WARN_ON_ONCE(!file_name))) {
fne = kmalloc(sizeof(*fne) + file_name->len + 1, gfp);
if (!fne)
goto out;
event = &fne->fae;
event->type = FANOTIFY_EVENT_TYPE_FID_NAME;
fne->name_len = file_name->len;
strcpy(fne->name, file_name->name);
goto init;
}
if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
ffe = kmem_cache_alloc(fanotify_fid_event_cachep, gfp);
if (!ffe)
goto out;
event = &ffe->fae;
event->type = FANOTIFY_EVENT_TYPE_FID;
} else {
struct fanotify_path_event *pevent;
pevent = kmem_cache_alloc(fanotify_path_event_cachep, gfp);
if (!pevent)
goto out;
event = &pevent->fae;
event->type = FANOTIFY_EVENT_TYPE_PATH;
}
init:
/*
* Use the victim inode instead of the watching inode as the id for
* event queue, so event reported on parent is merged with event
* reported on child when both directory and child watches exist.
*/
fsnotify_init_event(&event->fse, (unsigned long)id);
event->mask = mask;
if (FAN_GROUP_FLAG(group, FAN_REPORT_TID))
event->pid = get_pid(task_pid(current));
else
event->pid = get_pid(task_tgid(current));
if (fsid && fanotify_event_fsid(event))
*fanotify_event_fsid(event) = *fsid;
if (fanotify_event_object_fh(event))
fanotify_encode_fh(fanotify_event_object_fh(event), id, gfp);
if (fanotify_event_dir_fh(event))
fanotify_encode_fh(fanotify_event_dir_fh(event), id, gfp);
if (fanotify_event_has_path(event)) {
struct path *p = fanotify_event_path(event);
if (path) {
*p = *path;
path_get(path);
} else {
p->mnt = NULL;
p->dentry = NULL;
}
}
out:
memalloc_unuse_memcg();
return event;
}
/*
* Get cached fsid of the filesystem containing the object from any connector.
* All connectors are supposed to have the same fsid, but we do not verify that
* here.
*/
static __kernel_fsid_t fanotify_get_fsid(struct fsnotify_iter_info *iter_info)
{
int type;
__kernel_fsid_t fsid = {};
fsnotify_foreach_obj_type(type) {
struct fsnotify_mark_connector *conn;
if (!fsnotify_iter_should_report_type(iter_info, type))
continue;
conn = READ_ONCE(iter_info->marks[type]->connector);
/* Mark is just getting destroyed or created? */
if (!conn)
continue;
if (!(conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID))
continue;
/* Pairs with smp_wmb() in fsnotify_add_mark_list() */
smp_rmb();
fsid = conn->fsid;
if (WARN_ON_ONCE(!fsid.val[0] && !fsid.val[1]))
continue;
return fsid;
}
return fsid;
}
static int fanotify_handle_event(struct fsnotify_group *group,
struct inode *inode,
u32 mask, const void *data, int data_type,
const struct qstr *file_name, u32 cookie,
struct fsnotify_iter_info *iter_info)
{
int ret = 0;
struct fanotify_event *event;
struct fsnotify_event *fsn_event;
__kernel_fsid_t fsid = {};
BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
BUILD_BUG_ON(FAN_ATTRIB != FS_ATTRIB);
BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
BUILD_BUG_ON(FAN_MOVED_TO != FS_MOVED_TO);
BUILD_BUG_ON(FAN_MOVED_FROM != FS_MOVED_FROM);
BUILD_BUG_ON(FAN_CREATE != FS_CREATE);
BUILD_BUG_ON(FAN_DELETE != FS_DELETE);
BUILD_BUG_ON(FAN_DIR_MODIFY != FS_DIR_MODIFY);
BUILD_BUG_ON(FAN_DELETE_SELF != FS_DELETE_SELF);
BUILD_BUG_ON(FAN_MOVE_SELF != FS_MOVE_SELF);
BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC);
BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM);
BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 19);
mask = fanotify_group_event_mask(group, iter_info, mask, data,
data_type);
if (!mask)
return 0;
pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
mask);
if (fanotify_is_perm_event(mask)) {
/*
* fsnotify_prepare_user_wait() fails if we race with mark
* deletion. Just let the operation pass in that case.
*/
if (!fsnotify_prepare_user_wait(iter_info))
return 0;
}
if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
fsid = fanotify_get_fsid(iter_info);
/* Racing with mark destruction or creation? */
if (!fsid.val[0] && !fsid.val[1])
return 0;
}
event = fanotify_alloc_event(group, inode, mask, data, data_type,
file_name, &fsid);
ret = -ENOMEM;
if (unlikely(!event)) {
/*
* We don't queue overflow events for permission events as
* there the access is denied and so no event is in fact lost.
*/
if (!fanotify_is_perm_event(mask))
fsnotify_queue_overflow(group);
goto finish;
}
fsn_event = &event->fse;
ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
if (ret) {
/* Permission events shouldn't be merged */
BUG_ON(ret == 1 && mask & FANOTIFY_PERM_EVENTS);
/* Our event wasn't used in the end. Free it. */
fsnotify_destroy_event(group, fsn_event);
ret = 0;
} else if (fanotify_is_perm_event(mask)) {
ret = fanotify_get_response(group, FANOTIFY_PERM(event),
iter_info);
}
finish:
if (fanotify_is_perm_event(mask))
fsnotify_finish_user_wait(iter_info);
return ret;
}
static void fanotify_free_group_priv(struct fsnotify_group *group)
{
struct user_struct *user;
user = group->fanotify_data.user;
atomic_dec(&user->fanotify_listeners);
free_uid(user);
}
static void fanotify_free_path_event(struct fanotify_event *event)
{
path_put(fanotify_event_path(event));
kmem_cache_free(fanotify_path_event_cachep, FANOTIFY_PE(event));
}
static void fanotify_free_perm_event(struct fanotify_event *event)
{
path_put(fanotify_event_path(event));
kmem_cache_free(fanotify_perm_event_cachep, FANOTIFY_PERM(event));
}
static void fanotify_free_fid_event(struct fanotify_event *event)
{
struct fanotify_fid_event *ffe = FANOTIFY_FE(event);
if (fanotify_fh_has_ext_buf(&ffe->object_fh))
kfree(fanotify_fh_ext_buf(&ffe->object_fh));
kmem_cache_free(fanotify_fid_event_cachep, ffe);
}
static void fanotify_free_name_event(struct fanotify_event *event)
{
struct fanotify_name_event *fne = FANOTIFY_NE(event);
if (fanotify_fh_has_ext_buf(&fne->dir_fh))
kfree(fanotify_fh_ext_buf(&fne->dir_fh));
kfree(fne);
}
static void fanotify_free_event(struct fsnotify_event *fsn_event)
{
struct fanotify_event *event;
event = FANOTIFY_E(fsn_event);
put_pid(event->pid);
switch (event->type) {
case FANOTIFY_EVENT_TYPE_PATH:
fanotify_free_path_event(event);
break;
case FANOTIFY_EVENT_TYPE_PATH_PERM:
fanotify_free_perm_event(event);
break;
case FANOTIFY_EVENT_TYPE_FID:
fanotify_free_fid_event(event);
break;
case FANOTIFY_EVENT_TYPE_FID_NAME:
fanotify_free_name_event(event);
break;
default:
WARN_ON_ONCE(1);
}
}
static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
{
kmem_cache_free(fanotify_mark_cache, fsn_mark);
}
const struct fsnotify_ops fanotify_fsnotify_ops = {
.handle_event = fanotify_handle_event,
.free_group_priv = fanotify_free_group_priv,
.free_event = fanotify_free_event,
.free_mark = fanotify_free_mark,
};