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fanotify: create overflow event type

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The special overflow event is allocated as struct fanotify_path_event,
but with a null path.

Use a special event type to identify the overflow event, so the helper
fanotify_has_event_path() will always indicate a non null path.

Allocating the overflow event doesn't need any of the fancy stuff in
fanotify_alloc_event(), so create a simplified helper for allocating the
overflow event.

There is also no need to store and report the pid with an overflow event.

Link: https://lore.kernel.org/r/20200708111156.24659-7-amir73il@gmail.com
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Amir Goldstein 2020-07-08 14:11:42 +03:00 committed by Jan Kara
parent 956235afd1
commit b8a6c3a2f0
3 changed files with 36 additions and 27 deletions
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27
fs/notify/fanotify/fanotify.c
View file

@ -344,11 +344,11 @@ static struct inode *fanotify_fid_inode(struct inode *to_tell, u32 event_mask,
return 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)
static 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;
@ -426,8 +426,7 @@ struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
* 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;
fanotify_init_event(event, (unsigned long)id, mask);
if (FAN_GROUP_FLAG(group, FAN_REPORT_TID))
event->pid = get_pid(task_pid(current));
else
@ -443,15 +442,8 @@ struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
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;
}
*fanotify_event_path(event) = *path;
path_get(path);
}
out:
memalloc_unuse_memcg();
@ -640,6 +632,9 @@ static void fanotify_free_event(struct fsnotify_event *fsn_event)
case FANOTIFY_EVENT_TYPE_FID_NAME:
fanotify_free_name_event(event);
break;
case FANOTIFY_EVENT_TYPE_OVERFLOW:
kfree(event);
break;
default:
WARN_ON_ONCE(1);
}

15
fs/notify/fanotify/fanotify.h
View file

@ -63,6 +63,7 @@ enum fanotify_event_type {
FANOTIFY_EVENT_TYPE_FID_NAME, /* variable length */
FANOTIFY_EVENT_TYPE_PATH,
FANOTIFY_EVENT_TYPE_PATH_PERM,
FANOTIFY_EVENT_TYPE_OVERFLOW, /* struct fanotify_event */
};
struct fanotify_event {
@ -72,6 +73,14 @@ struct fanotify_event {
struct pid *pid;
};
static inline void fanotify_init_event(struct fanotify_event *event,
unsigned long id, u32 mask)
{
fsnotify_init_event(&event->fse, id);
event->mask = mask;
event->pid = NULL;
}
struct fanotify_fid_event {
struct fanotify_event fae;
__kernel_fsid_t fsid;
@ -202,9 +211,3 @@ static inline struct path *fanotify_event_path(struct fanotify_event *event)
else
return NULL;
}
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);

21
fs/notify/fanotify/fanotify_user.c
View file

@ -836,13 +836,26 @@ static int fanotify_add_inode_mark(struct fsnotify_group *group,
FSNOTIFY_OBJ_TYPE_INODE, mask, flags, fsid);
}
static struct fsnotify_event *fanotify_alloc_overflow_event(void)
{
struct fanotify_event *oevent;
oevent = kmalloc(sizeof(*oevent), GFP_KERNEL_ACCOUNT);
if (!oevent)
return NULL;
fanotify_init_event(oevent, 0, FS_Q_OVERFLOW);
oevent->type = FANOTIFY_EVENT_TYPE_OVERFLOW;
return &oevent->fse;
}
/* fanotify syscalls */
SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
{
struct fsnotify_group *group;
int f_flags, fd;
struct user_struct *user;
struct fanotify_event *oevent;
pr_debug("%s: flags=%x event_f_flags=%x\n",
__func__, flags, event_f_flags);
@ -897,13 +910,11 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
atomic_inc(&user->fanotify_listeners);
group->memcg = get_mem_cgroup_from_mm(current->mm);
oevent = fanotify_alloc_event(group, NULL, FS_Q_OVERFLOW, NULL,
FSNOTIFY_EVENT_NONE, NULL, NULL);
if (unlikely(!oevent)) {
group->overflow_event = fanotify_alloc_overflow_event();
if (unlikely(!group->overflow_event)) {
fd = -ENOMEM;
goto out_destroy_group;
}
group->overflow_event = &oevent->fse;
if (force_o_largefile())
event_f_flags |= O_LARGEFILE;