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09a3dac7b5
In bpf_pid_task_storage_update_elem(), it missed to
test the !task_storage_ptr(task) which then could trigger a NULL
pointer exception in bpf_local_storage_update().
Fixes: 4cf1bc1f10
("bpf: Implement task local storage")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Roman Gushchin <guro@fb.com>
Acked-by: KP Singh <kpsingh@google.com>
Link: https://lore.kernel.org/bpf/20201112001919.2028357-1-kafai@fb.com
316 lines
7.9 KiB
C
316 lines
7.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (c) 2020 Facebook
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* Copyright 2020 Google LLC.
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*/
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#include <linux/pid.h>
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#include <linux/sched.h>
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#include <linux/rculist.h>
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#include <linux/list.h>
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#include <linux/hash.h>
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#include <linux/types.h>
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#include <linux/spinlock.h>
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#include <linux/bpf.h>
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#include <linux/bpf_local_storage.h>
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#include <linux/filter.h>
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#include <uapi/linux/btf.h>
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#include <linux/bpf_lsm.h>
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#include <linux/btf_ids.h>
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#include <linux/fdtable.h>
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DEFINE_BPF_STORAGE_CACHE(task_cache);
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static struct bpf_local_storage __rcu **task_storage_ptr(void *owner)
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{
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struct task_struct *task = owner;
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struct bpf_storage_blob *bsb;
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bsb = bpf_task(task);
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if (!bsb)
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return NULL;
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return &bsb->storage;
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}
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static struct bpf_local_storage_data *
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task_storage_lookup(struct task_struct *task, struct bpf_map *map,
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bool cacheit_lockit)
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{
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struct bpf_local_storage *task_storage;
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struct bpf_local_storage_map *smap;
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struct bpf_storage_blob *bsb;
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bsb = bpf_task(task);
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if (!bsb)
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return NULL;
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task_storage = rcu_dereference(bsb->storage);
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if (!task_storage)
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return NULL;
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smap = (struct bpf_local_storage_map *)map;
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return bpf_local_storage_lookup(task_storage, smap, cacheit_lockit);
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}
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void bpf_task_storage_free(struct task_struct *task)
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{
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struct bpf_local_storage_elem *selem;
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struct bpf_local_storage *local_storage;
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bool free_task_storage = false;
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struct bpf_storage_blob *bsb;
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struct hlist_node *n;
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bsb = bpf_task(task);
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if (!bsb)
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return;
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rcu_read_lock();
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local_storage = rcu_dereference(bsb->storage);
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if (!local_storage) {
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rcu_read_unlock();
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return;
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}
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/* Neither the bpf_prog nor the bpf-map's syscall
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* could be modifying the local_storage->list now.
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* Thus, no elem can be added-to or deleted-from the
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* local_storage->list by the bpf_prog or by the bpf-map's syscall.
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*
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* It is racing with bpf_local_storage_map_free() alone
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* when unlinking elem from the local_storage->list and
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* the map's bucket->list.
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*/
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raw_spin_lock_bh(&local_storage->lock);
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hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
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/* Always unlink from map before unlinking from
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* local_storage.
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*/
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bpf_selem_unlink_map(selem);
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free_task_storage = bpf_selem_unlink_storage_nolock(
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local_storage, selem, false);
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}
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raw_spin_unlock_bh(&local_storage->lock);
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rcu_read_unlock();
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/* free_task_storage should always be true as long as
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* local_storage->list was non-empty.
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*/
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if (free_task_storage)
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kfree_rcu(local_storage, rcu);
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}
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static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key)
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{
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struct bpf_local_storage_data *sdata;
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struct task_struct *task;
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unsigned int f_flags;
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struct pid *pid;
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int fd, err;
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fd = *(int *)key;
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pid = pidfd_get_pid(fd, &f_flags);
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if (IS_ERR(pid))
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return ERR_CAST(pid);
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/* We should be in an RCU read side critical section, it should be safe
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* to call pid_task.
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*/
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WARN_ON_ONCE(!rcu_read_lock_held());
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task = pid_task(pid, PIDTYPE_PID);
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if (!task) {
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err = -ENOENT;
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goto out;
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}
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sdata = task_storage_lookup(task, map, true);
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put_pid(pid);
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return sdata ? sdata->data : NULL;
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out:
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put_pid(pid);
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return ERR_PTR(err);
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}
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static int bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key,
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void *value, u64 map_flags)
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{
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struct bpf_local_storage_data *sdata;
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struct task_struct *task;
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unsigned int f_flags;
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struct pid *pid;
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int fd, err;
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fd = *(int *)key;
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pid = pidfd_get_pid(fd, &f_flags);
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if (IS_ERR(pid))
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return PTR_ERR(pid);
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/* We should be in an RCU read side critical section, it should be safe
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* to call pid_task.
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*/
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WARN_ON_ONCE(!rcu_read_lock_held());
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task = pid_task(pid, PIDTYPE_PID);
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if (!task || !task_storage_ptr(task)) {
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err = -ENOENT;
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goto out;
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}
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sdata = bpf_local_storage_update(
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task, (struct bpf_local_storage_map *)map, value, map_flags);
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err = PTR_ERR_OR_ZERO(sdata);
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out:
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put_pid(pid);
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return err;
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}
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static int task_storage_delete(struct task_struct *task, struct bpf_map *map)
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{
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struct bpf_local_storage_data *sdata;
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sdata = task_storage_lookup(task, map, false);
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if (!sdata)
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return -ENOENT;
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bpf_selem_unlink(SELEM(sdata));
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return 0;
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}
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static int bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key)
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{
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struct task_struct *task;
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unsigned int f_flags;
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struct pid *pid;
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int fd, err;
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fd = *(int *)key;
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pid = pidfd_get_pid(fd, &f_flags);
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if (IS_ERR(pid))
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return PTR_ERR(pid);
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/* We should be in an RCU read side critical section, it should be safe
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* to call pid_task.
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*/
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WARN_ON_ONCE(!rcu_read_lock_held());
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task = pid_task(pid, PIDTYPE_PID);
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if (!task) {
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err = -ENOENT;
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goto out;
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}
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err = task_storage_delete(task, map);
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out:
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put_pid(pid);
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return err;
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}
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BPF_CALL_4(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
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task, void *, value, u64, flags)
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{
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struct bpf_local_storage_data *sdata;
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if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
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return (unsigned long)NULL;
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/* explicitly check that the task_storage_ptr is not
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* NULL as task_storage_lookup returns NULL in this case and
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* bpf_local_storage_update expects the owner to have a
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* valid storage pointer.
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*/
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if (!task_storage_ptr(task))
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return (unsigned long)NULL;
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sdata = task_storage_lookup(task, map, true);
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if (sdata)
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return (unsigned long)sdata->data;
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/* This helper must only be called from places where the lifetime of the task
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* is guaranteed. Either by being refcounted or by being protected
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* by an RCU read-side critical section.
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*/
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if (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) {
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sdata = bpf_local_storage_update(
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task, (struct bpf_local_storage_map *)map, value,
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BPF_NOEXIST);
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return IS_ERR(sdata) ? (unsigned long)NULL :
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(unsigned long)sdata->data;
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}
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return (unsigned long)NULL;
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}
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BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *,
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task)
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{
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/* This helper must only be called from places where the lifetime of the task
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* is guaranteed. Either by being refcounted or by being protected
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* by an RCU read-side critical section.
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*/
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return task_storage_delete(task, map);
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}
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static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)
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{
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return -ENOTSUPP;
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}
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static struct bpf_map *task_storage_map_alloc(union bpf_attr *attr)
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{
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struct bpf_local_storage_map *smap;
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smap = bpf_local_storage_map_alloc(attr);
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if (IS_ERR(smap))
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return ERR_CAST(smap);
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smap->cache_idx = bpf_local_storage_cache_idx_get(&task_cache);
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return &smap->map;
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}
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static void task_storage_map_free(struct bpf_map *map)
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{
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struct bpf_local_storage_map *smap;
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smap = (struct bpf_local_storage_map *)map;
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bpf_local_storage_cache_idx_free(&task_cache, smap->cache_idx);
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bpf_local_storage_map_free(smap);
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}
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static int task_storage_map_btf_id;
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const struct bpf_map_ops task_storage_map_ops = {
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.map_meta_equal = bpf_map_meta_equal,
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.map_alloc_check = bpf_local_storage_map_alloc_check,
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.map_alloc = task_storage_map_alloc,
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.map_free = task_storage_map_free,
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.map_get_next_key = notsupp_get_next_key,
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.map_lookup_elem = bpf_pid_task_storage_lookup_elem,
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.map_update_elem = bpf_pid_task_storage_update_elem,
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.map_delete_elem = bpf_pid_task_storage_delete_elem,
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.map_check_btf = bpf_local_storage_map_check_btf,
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.map_btf_name = "bpf_local_storage_map",
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.map_btf_id = &task_storage_map_btf_id,
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.map_owner_storage_ptr = task_storage_ptr,
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};
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BTF_ID_LIST_SINGLE(bpf_task_storage_btf_ids, struct, task_struct)
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const struct bpf_func_proto bpf_task_storage_get_proto = {
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.func = bpf_task_storage_get,
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.gpl_only = false,
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.ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
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.arg1_type = ARG_CONST_MAP_PTR,
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.arg2_type = ARG_PTR_TO_BTF_ID,
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.arg2_btf_id = &bpf_task_storage_btf_ids[0],
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.arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
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.arg4_type = ARG_ANYTHING,
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};
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const struct bpf_func_proto bpf_task_storage_delete_proto = {
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.func = bpf_task_storage_delete,
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.gpl_only = false,
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.ret_type = RET_INTEGER,
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.arg1_type = ARG_CONST_MAP_PTR,
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.arg2_type = ARG_PTR_TO_BTF_ID,
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.arg2_btf_id = &bpf_task_storage_btf_ids[0],
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};
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