gpio: rcar: Fix runtime PM imbalance on error

[linux/fpc-iii.git] / fs / notify / fanotify / fanotify.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 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 (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];
                /*
                 * 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;
                marks_ignored_mask |= mark->ignored_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) != 20);

        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,
};