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![Tetsuo Handa](/assets/img/avatar_default.png)
[ Upstream commitc03a0fd0b6
] syzbot is hitting use-after-free bug in uinput module [1]. This is because kobject_uevent(KOBJ_REMOVE) is called again due to commit0f4dafc056
("Kobject: auto-cleanup on final unref") after memory allocation fault injection made kobject_uevent(KOBJ_REMOVE) from device_del() from input_unregister_device() fail, while uinput_destroy_device() is expecting that kobject_uevent(KOBJ_REMOVE) is not called after device_del() from input_unregister_device() completed. That commit intended to catch cases where nobody even attempted to send "remove" uevents. But there is no guarantee that an event will ultimately be sent. We are at the point of no return as far as the rest of the kernel is concerned; there are no repeats or do-overs. Also, it is not clear whether some subsystem depends on that commit. If no subsystem depends on that commit, it will be better to remove the state_{add,remove}_uevent_sent logic. But we don't want to risk a regression (in a patch which will be backported) by trying to remove that logic. Therefore, as a first step, let's avoid the use-after-free bug by making sure that kobject_uevent(KOBJ_REMOVE) won't be triggered twice. [1] https://syzkaller.appspot.com/bug?id=8b17c134fe938bbddd75a45afaa9e68af43a362d Reported-by: syzbot <syzbot+f648cfb7e0b52bf7ae32@syzkaller.appspotmail.com> Analyzed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Fixes:0f4dafc056
("Kobject: auto-cleanup on final unref") Cc: Kay Sievers <kay@vrfy.org> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
650 lines
15 KiB
C
650 lines
15 KiB
C
/*
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* kernel userspace event delivery
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*
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* Copyright (C) 2004 Red Hat, Inc. All rights reserved.
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* Copyright (C) 2004 Novell, Inc. All rights reserved.
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* Copyright (C) 2004 IBM, Inc. All rights reserved.
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*
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* Licensed under the GNU GPL v2.
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*
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* Authors:
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* Robert Love <rml@novell.com>
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* Kay Sievers <kay.sievers@vrfy.org>
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* Arjan van de Ven <arjanv@redhat.com>
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* Greg Kroah-Hartman <greg@kroah.com>
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*/
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#include <linux/spinlock.h>
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#include <linux/string.h>
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#include <linux/kobject.h>
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#include <linux/export.h>
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#include <linux/kmod.h>
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#include <linux/slab.h>
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#include <linux/socket.h>
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#include <linux/skbuff.h>
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#include <linux/netlink.h>
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#include <linux/uuid.h>
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#include <linux/ctype.h>
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#include <net/sock.h>
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#include <net/net_namespace.h>
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u64 uevent_seqnum;
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#ifdef CONFIG_UEVENT_HELPER
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char uevent_helper[UEVENT_HELPER_PATH_LEN] = CONFIG_UEVENT_HELPER_PATH;
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#endif
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#ifdef CONFIG_NET
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struct uevent_sock {
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struct list_head list;
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struct sock *sk;
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};
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static LIST_HEAD(uevent_sock_list);
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#endif
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/* This lock protects uevent_seqnum and uevent_sock_list */
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static DEFINE_MUTEX(uevent_sock_mutex);
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/* the strings here must match the enum in include/linux/kobject.h */
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static const char *kobject_actions[] = {
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[KOBJ_ADD] = "add",
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[KOBJ_REMOVE] = "remove",
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[KOBJ_CHANGE] = "change",
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[KOBJ_MOVE] = "move",
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[KOBJ_ONLINE] = "online",
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[KOBJ_OFFLINE] = "offline",
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[KOBJ_BIND] = "bind",
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[KOBJ_UNBIND] = "unbind",
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};
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static int kobject_action_type(const char *buf, size_t count,
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enum kobject_action *type,
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const char **args)
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{
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enum kobject_action action;
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size_t count_first;
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const char *args_start;
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int ret = -EINVAL;
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if (count && (buf[count-1] == '\n' || buf[count-1] == '\0'))
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count--;
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if (!count)
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goto out;
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args_start = strnchr(buf, count, ' ');
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if (args_start) {
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count_first = args_start - buf;
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args_start = args_start + 1;
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} else
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count_first = count;
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for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
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if (strncmp(kobject_actions[action], buf, count_first) != 0)
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continue;
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if (kobject_actions[action][count_first] != '\0')
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continue;
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if (args)
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*args = args_start;
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*type = action;
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ret = 0;
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break;
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}
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out:
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return ret;
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}
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static const char *action_arg_word_end(const char *buf, const char *buf_end,
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char delim)
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{
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const char *next = buf;
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while (next <= buf_end && *next != delim)
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if (!isalnum(*next++))
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return NULL;
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if (next == buf)
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return NULL;
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return next;
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}
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static int kobject_action_args(const char *buf, size_t count,
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struct kobj_uevent_env **ret_env)
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{
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struct kobj_uevent_env *env = NULL;
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const char *next, *buf_end, *key;
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int key_len;
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int r = -EINVAL;
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if (count && (buf[count - 1] == '\n' || buf[count - 1] == '\0'))
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count--;
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if (!count)
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return -EINVAL;
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env = kzalloc(sizeof(*env), GFP_KERNEL);
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if (!env)
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return -ENOMEM;
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/* first arg is UUID */
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if (count < UUID_STRING_LEN || !uuid_is_valid(buf) ||
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add_uevent_var(env, "SYNTH_UUID=%.*s", UUID_STRING_LEN, buf))
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goto out;
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/*
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* the rest are custom environment variables in KEY=VALUE
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* format with ' ' delimiter between each KEY=VALUE pair
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*/
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next = buf + UUID_STRING_LEN;
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buf_end = buf + count - 1;
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while (next <= buf_end) {
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if (*next != ' ')
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goto out;
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/* skip the ' ', key must follow */
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key = ++next;
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if (key > buf_end)
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goto out;
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buf = next;
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next = action_arg_word_end(buf, buf_end, '=');
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if (!next || next > buf_end || *next != '=')
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goto out;
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key_len = next - buf;
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/* skip the '=', value must follow */
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if (++next > buf_end)
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goto out;
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buf = next;
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next = action_arg_word_end(buf, buf_end, ' ');
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if (!next)
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goto out;
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if (add_uevent_var(env, "SYNTH_ARG_%.*s=%.*s",
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key_len, key, (int) (next - buf), buf))
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goto out;
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}
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r = 0;
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out:
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if (r)
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kfree(env);
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else
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*ret_env = env;
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return r;
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}
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/**
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* kobject_synth_uevent - send synthetic uevent with arguments
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*
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* @kobj: struct kobject for which synthetic uevent is to be generated
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* @buf: buffer containing action type and action args, newline is ignored
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* @count: length of buffer
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*
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* Returns 0 if kobject_synthetic_uevent() is completed with success or the
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* corresponding error when it fails.
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*/
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int kobject_synth_uevent(struct kobject *kobj, const char *buf, size_t count)
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{
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char *no_uuid_envp[] = { "SYNTH_UUID=0", NULL };
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enum kobject_action action;
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const char *action_args;
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struct kobj_uevent_env *env;
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const char *msg = NULL, *devpath;
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int r;
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r = kobject_action_type(buf, count, &action, &action_args);
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if (r) {
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msg = "unknown uevent action string\n";
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goto out;
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}
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if (!action_args) {
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r = kobject_uevent_env(kobj, action, no_uuid_envp);
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goto out;
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}
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r = kobject_action_args(action_args,
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count - (action_args - buf), &env);
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if (r == -EINVAL) {
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msg = "incorrect uevent action arguments\n";
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goto out;
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}
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if (r)
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goto out;
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r = kobject_uevent_env(kobj, action, env->envp);
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kfree(env);
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out:
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if (r) {
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devpath = kobject_get_path(kobj, GFP_KERNEL);
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printk(KERN_WARNING "synth uevent: %s: %s",
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devpath ?: "unknown device",
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msg ?: "failed to send uevent");
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kfree(devpath);
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}
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return r;
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}
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#ifdef CONFIG_NET
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static int kobj_bcast_filter(struct sock *dsk, struct sk_buff *skb, void *data)
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{
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struct kobject *kobj = data, *ksobj;
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const struct kobj_ns_type_operations *ops;
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ops = kobj_ns_ops(kobj);
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if (!ops && kobj->kset) {
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ksobj = &kobj->kset->kobj;
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if (ksobj->parent != NULL)
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ops = kobj_ns_ops(ksobj->parent);
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}
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if (ops && ops->netlink_ns && kobj->ktype->namespace) {
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const void *sock_ns, *ns;
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ns = kobj->ktype->namespace(kobj);
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sock_ns = ops->netlink_ns(dsk);
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return sock_ns != ns;
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}
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return 0;
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}
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#endif
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#ifdef CONFIG_UEVENT_HELPER
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static int kobj_usermode_filter(struct kobject *kobj)
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{
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const struct kobj_ns_type_operations *ops;
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ops = kobj_ns_ops(kobj);
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if (ops) {
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const void *init_ns, *ns;
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ns = kobj->ktype->namespace(kobj);
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init_ns = ops->initial_ns();
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return ns != init_ns;
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}
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return 0;
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}
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static int init_uevent_argv(struct kobj_uevent_env *env, const char *subsystem)
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{
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int len;
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len = strlcpy(&env->buf[env->buflen], subsystem,
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sizeof(env->buf) - env->buflen);
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if (len >= (sizeof(env->buf) - env->buflen)) {
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WARN(1, KERN_ERR "init_uevent_argv: buffer size too small\n");
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return -ENOMEM;
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}
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env->argv[0] = uevent_helper;
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env->argv[1] = &env->buf[env->buflen];
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env->argv[2] = NULL;
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env->buflen += len + 1;
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return 0;
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}
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static void cleanup_uevent_env(struct subprocess_info *info)
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{
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kfree(info->data);
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}
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#endif
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static void zap_modalias_env(struct kobj_uevent_env *env)
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{
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static const char modalias_prefix[] = "MODALIAS=";
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int i;
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for (i = 0; i < env->envp_idx;) {
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if (strncmp(env->envp[i], modalias_prefix,
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sizeof(modalias_prefix) - 1)) {
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i++;
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continue;
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}
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if (i != env->envp_idx - 1)
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memmove(&env->envp[i], &env->envp[i + 1],
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sizeof(env->envp[i]) * env->envp_idx - 1);
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env->envp_idx--;
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}
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}
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/**
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* kobject_uevent_env - send an uevent with environmental data
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*
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* @kobj: struct kobject that the action is happening to
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* @action: action that is happening
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* @envp_ext: pointer to environmental data
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*
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* Returns 0 if kobject_uevent_env() is completed with success or the
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* corresponding error when it fails.
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*/
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int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
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char *envp_ext[])
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{
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struct kobj_uevent_env *env;
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const char *action_string = kobject_actions[action];
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const char *devpath = NULL;
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const char *subsystem;
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struct kobject *top_kobj;
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struct kset *kset;
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const struct kset_uevent_ops *uevent_ops;
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int i = 0;
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int retval = 0;
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#ifdef CONFIG_NET
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struct uevent_sock *ue_sk;
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#endif
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/*
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* Mark "remove" event done regardless of result, for some subsystems
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* do not want to re-trigger "remove" event via automatic cleanup.
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*/
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if (action == KOBJ_REMOVE)
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kobj->state_remove_uevent_sent = 1;
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pr_debug("kobject: '%s' (%p): %s\n",
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kobject_name(kobj), kobj, __func__);
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/* search the kset we belong to */
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top_kobj = kobj;
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while (!top_kobj->kset && top_kobj->parent)
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top_kobj = top_kobj->parent;
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if (!top_kobj->kset) {
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pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
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"without kset!\n", kobject_name(kobj), kobj,
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__func__);
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return -EINVAL;
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}
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kset = top_kobj->kset;
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uevent_ops = kset->uevent_ops;
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/* skip the event, if uevent_suppress is set*/
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if (kobj->uevent_suppress) {
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pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
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"caused the event to drop!\n",
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kobject_name(kobj), kobj, __func__);
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return 0;
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}
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/* skip the event, if the filter returns zero. */
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if (uevent_ops && uevent_ops->filter)
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if (!uevent_ops->filter(kset, kobj)) {
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pr_debug("kobject: '%s' (%p): %s: filter function "
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"caused the event to drop!\n",
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kobject_name(kobj), kobj, __func__);
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return 0;
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}
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/* originating subsystem */
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if (uevent_ops && uevent_ops->name)
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subsystem = uevent_ops->name(kset, kobj);
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else
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subsystem = kobject_name(&kset->kobj);
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if (!subsystem) {
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pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
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"event to drop!\n", kobject_name(kobj), kobj,
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__func__);
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return 0;
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}
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/* environment buffer */
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env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
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if (!env)
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return -ENOMEM;
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/* complete object path */
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devpath = kobject_get_path(kobj, GFP_KERNEL);
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if (!devpath) {
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retval = -ENOENT;
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goto exit;
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}
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/* default keys */
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retval = add_uevent_var(env, "ACTION=%s", action_string);
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if (retval)
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goto exit;
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retval = add_uevent_var(env, "DEVPATH=%s", devpath);
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if (retval)
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goto exit;
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retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
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if (retval)
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goto exit;
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/* keys passed in from the caller */
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if (envp_ext) {
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for (i = 0; envp_ext[i]; i++) {
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retval = add_uevent_var(env, "%s", envp_ext[i]);
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if (retval)
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goto exit;
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}
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}
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/* let the kset specific function add its stuff */
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if (uevent_ops && uevent_ops->uevent) {
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retval = uevent_ops->uevent(kset, kobj, env);
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if (retval) {
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pr_debug("kobject: '%s' (%p): %s: uevent() returned "
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"%d\n", kobject_name(kobj), kobj,
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__func__, retval);
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goto exit;
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}
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}
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switch (action) {
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case KOBJ_ADD:
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/*
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* Mark "add" event so we can make sure we deliver "remove"
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* event to userspace during automatic cleanup. If
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* the object did send an "add" event, "remove" will
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* automatically generated by the core, if not already done
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* by the caller.
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*/
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kobj->state_add_uevent_sent = 1;
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break;
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case KOBJ_UNBIND:
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zap_modalias_env(env);
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break;
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default:
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break;
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}
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mutex_lock(&uevent_sock_mutex);
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/* we will send an event, so request a new sequence number */
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retval = add_uevent_var(env, "SEQNUM=%llu", (unsigned long long)++uevent_seqnum);
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if (retval) {
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mutex_unlock(&uevent_sock_mutex);
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goto exit;
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}
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#if defined(CONFIG_NET)
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/* send netlink message */
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list_for_each_entry(ue_sk, &uevent_sock_list, list) {
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struct sock *uevent_sock = ue_sk->sk;
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struct sk_buff *skb;
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size_t len;
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if (!netlink_has_listeners(uevent_sock, 1))
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continue;
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/* allocate message with the maximum possible size */
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len = strlen(action_string) + strlen(devpath) + 2;
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skb = alloc_skb(len + env->buflen, GFP_KERNEL);
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if (skb) {
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char *scratch;
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/* add header */
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scratch = skb_put(skb, len);
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sprintf(scratch, "%s@%s", action_string, devpath);
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/* copy keys to our continuous event payload buffer */
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for (i = 0; i < env->envp_idx; i++) {
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len = strlen(env->envp[i]) + 1;
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scratch = skb_put(skb, len);
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strcpy(scratch, env->envp[i]);
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}
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|
|
NETLINK_CB(skb).dst_group = 1;
|
|
retval = netlink_broadcast_filtered(uevent_sock, skb,
|
|
0, 1, GFP_KERNEL,
|
|
kobj_bcast_filter,
|
|
kobj);
|
|
/* ENOBUFS should be handled in userspace */
|
|
if (retval == -ENOBUFS || retval == -ESRCH)
|
|
retval = 0;
|
|
} else
|
|
retval = -ENOMEM;
|
|
}
|
|
#endif
|
|
mutex_unlock(&uevent_sock_mutex);
|
|
|
|
#ifdef CONFIG_UEVENT_HELPER
|
|
/* call uevent_helper, usually only enabled during early boot */
|
|
if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
|
|
struct subprocess_info *info;
|
|
|
|
retval = add_uevent_var(env, "HOME=/");
|
|
if (retval)
|
|
goto exit;
|
|
retval = add_uevent_var(env,
|
|
"PATH=/sbin:/bin:/usr/sbin:/usr/bin");
|
|
if (retval)
|
|
goto exit;
|
|
retval = init_uevent_argv(env, subsystem);
|
|
if (retval)
|
|
goto exit;
|
|
|
|
retval = -ENOMEM;
|
|
info = call_usermodehelper_setup(env->argv[0], env->argv,
|
|
env->envp, GFP_KERNEL,
|
|
NULL, cleanup_uevent_env, env);
|
|
if (info) {
|
|
retval = call_usermodehelper_exec(info, UMH_NO_WAIT);
|
|
env = NULL; /* freed by cleanup_uevent_env */
|
|
}
|
|
}
|
|
#endif
|
|
|
|
exit:
|
|
kfree(devpath);
|
|
kfree(env);
|
|
return retval;
|
|
}
|
|
EXPORT_SYMBOL_GPL(kobject_uevent_env);
|
|
|
|
/**
|
|
* kobject_uevent - notify userspace by sending an uevent
|
|
*
|
|
* @kobj: struct kobject that the action is happening to
|
|
* @action: action that is happening
|
|
*
|
|
* Returns 0 if kobject_uevent() is completed with success or the
|
|
* corresponding error when it fails.
|
|
*/
|
|
int kobject_uevent(struct kobject *kobj, enum kobject_action action)
|
|
{
|
|
return kobject_uevent_env(kobj, action, NULL);
|
|
}
|
|
EXPORT_SYMBOL_GPL(kobject_uevent);
|
|
|
|
/**
|
|
* add_uevent_var - add key value string to the environment buffer
|
|
* @env: environment buffer structure
|
|
* @format: printf format for the key=value pair
|
|
*
|
|
* Returns 0 if environment variable was added successfully or -ENOMEM
|
|
* if no space was available.
|
|
*/
|
|
int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
|
|
{
|
|
va_list args;
|
|
int len;
|
|
|
|
if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
|
|
WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
|
|
return -ENOMEM;
|
|
}
|
|
|
|
va_start(args, format);
|
|
len = vsnprintf(&env->buf[env->buflen],
|
|
sizeof(env->buf) - env->buflen,
|
|
format, args);
|
|
va_end(args);
|
|
|
|
if (len >= (sizeof(env->buf) - env->buflen)) {
|
|
WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
|
|
return -ENOMEM;
|
|
}
|
|
|
|
env->envp[env->envp_idx++] = &env->buf[env->buflen];
|
|
env->buflen += len + 1;
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(add_uevent_var);
|
|
|
|
#if defined(CONFIG_NET)
|
|
static int uevent_net_init(struct net *net)
|
|
{
|
|
struct uevent_sock *ue_sk;
|
|
struct netlink_kernel_cfg cfg = {
|
|
.groups = 1,
|
|
.flags = NL_CFG_F_NONROOT_RECV,
|
|
};
|
|
|
|
ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL);
|
|
if (!ue_sk)
|
|
return -ENOMEM;
|
|
|
|
ue_sk->sk = netlink_kernel_create(net, NETLINK_KOBJECT_UEVENT, &cfg);
|
|
if (!ue_sk->sk) {
|
|
printk(KERN_ERR
|
|
"kobject_uevent: unable to create netlink socket!\n");
|
|
kfree(ue_sk);
|
|
return -ENODEV;
|
|
}
|
|
mutex_lock(&uevent_sock_mutex);
|
|
list_add_tail(&ue_sk->list, &uevent_sock_list);
|
|
mutex_unlock(&uevent_sock_mutex);
|
|
return 0;
|
|
}
|
|
|
|
static void uevent_net_exit(struct net *net)
|
|
{
|
|
struct uevent_sock *ue_sk;
|
|
|
|
mutex_lock(&uevent_sock_mutex);
|
|
list_for_each_entry(ue_sk, &uevent_sock_list, list) {
|
|
if (sock_net(ue_sk->sk) == net)
|
|
goto found;
|
|
}
|
|
mutex_unlock(&uevent_sock_mutex);
|
|
return;
|
|
|
|
found:
|
|
list_del(&ue_sk->list);
|
|
mutex_unlock(&uevent_sock_mutex);
|
|
|
|
netlink_kernel_release(ue_sk->sk);
|
|
kfree(ue_sk);
|
|
}
|
|
|
|
static struct pernet_operations uevent_net_ops = {
|
|
.init = uevent_net_init,
|
|
.exit = uevent_net_exit,
|
|
};
|
|
|
|
static int __init kobject_uevent_init(void)
|
|
{
|
|
return register_pernet_subsys(&uevent_net_ops);
|
|
}
|
|
|
|
|
|
postcore_initcall(kobject_uevent_init);
|
|
#endif
|