Commit message: appletalk: Fix use-after-free in atalk_proc_exit

KASAN report this:

BUG: KASAN: use-after-free in pde_subdir_find+0x12d/0x150 fs/proc/generic.c:71
Read of size 8 at addr ffff8881f41fe5b0 by task syz-executor.0/2806

CPU: 0 PID: 2806 Comm: syz-executor.0 Not tainted 5.0.0-rc7+ #45
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0xfa/0x1ce lib/dump_stack.c:113
 print_address_description+0x65/0x270 mm/kasan/report.c:187
 kasan_report+0x149/0x18d mm/kasan/report.c:317
 pde_subdir_find+0x12d/0x150 fs/proc/generic.c:71
 remove_proc_entry+0xe8/0x420 fs/proc/generic.c:667
 atalk_proc_exit+0x18/0x820 [appletalk]
 atalk_exit+0xf/0x5a [appletalk]
 __do_sys_delete_module kernel/module.c:1018 [inline]
 __se_sys_delete_module kernel/module.c:961 [inline]
 __x64_sys_delete_module+0x3dc/0x5e0 kernel/module.c:961
 do_syscall_64+0x147/0x600 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x462e99
Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fb2de6b9c58 EFLAGS: 00000246 ORIG_RAX: 00000000000000b0
RAX: ffffffffffffffda RBX: 000000000073bf00 RCX: 0000000000462e99
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200001c0
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb2de6ba6bc
R13: 00000000004bccaa R14: 00000000006f6bc8 R15: 00000000ffffffff

Allocated by task 2806:
 set_track mm/kasan/common.c:85 [inline]
 __kasan_kmalloc.constprop.3+0xa0/0xd0 mm/kasan/common.c:496
 slab_post_alloc_hook mm/slab.h:444 [inline]
 slab_alloc_node mm/slub.c:2739 [inline]
 slab_alloc mm/slub.c:2747 [inline]
 kmem_cache_alloc+0xcf/0x250 mm/slub.c:2752
 kmem_cache_zalloc include/linux/slab.h:730 [inline]
 __proc_create+0x30f/0xa20 fs/proc/generic.c:408
 proc_mkdir_data+0x47/0x190 fs/proc/generic.c:469
 0xffffffffc10c01bb
 0xffffffffc10c0166
 do_one_initcall+0xfa/0x5ca init/main.c:887
 do_init_module+0x204/0x5f6 kernel/module.c:3460
 load_module+0x66b2/0x8570 kernel/module.c:3808
 __do_sys_finit_module+0x238/0x2a0 kernel/module.c:3902
 do_syscall_64+0x147/0x600 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 2806:
 set_track mm/kasan/common.c:85 [inline]
 __kasan_slab_free+0x130/0x180 mm/kasan/common.c:458
 slab_free_hook mm/slub.c:1409 [inline]
 slab_free_freelist_hook mm/slub.c:1436 [inline]
 slab_free mm/slub.c:2986 [inline]
 kmem_cache_free+0xa6/0x2a0 mm/slub.c:3002
 pde_put+0x6e/0x80 fs/proc/generic.c:647
 remove_proc_entry+0x1d3/0x420 fs/proc/generic.c:684
 0xffffffffc10c031c
 0xffffffffc10c0166
 do_one_initcall+0xfa/0x5ca init/main.c:887
 do_init_module+0x204/0x5f6 kernel/module.c:3460
 load_module+0x66b2/0x8570 kernel/module.c:3808
 __do_sys_finit_module+0x238/0x2a0 kernel/module.c:3902
 do_syscall_64+0x147/0x600 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8881f41fe500
 which belongs to the cache proc_dir_entry of size 256
The buggy address is located 176 bytes inside of
 256-byte region [ffff8881f41fe500, ffff8881f41fe600)
The buggy address belongs to the page:
page:ffffea0007d07f80 count:1 mapcount:0 mapping:ffff8881f6e69a00 index:0x0
flags: 0x2fffc0000000200(slab)
raw: 02fffc0000000200 dead000000000100 dead000000000200 ffff8881f6e69a00
raw: 0000000000000000 00000000800c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881f41fe480: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff8881f41fe500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881f41fe580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff8881f41fe600: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff8881f41fe680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

It should check the return value of atalk_proc_init fails,
otherwise atalk_exit will trgger use-after-free in pde_subdir_find
while unload the module.This patch fix error cleanup path of atalk_init

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
CVE: CVE-2019-15292
CWE: CWE-416
Vulnerability description: An issue was discovered in the Linux kernel before 5.0.9. There is a use-after-free in atalk_proc_exit, related to net/appletalk/atalk_proc.c, net/appletalk/ddp.c, and net/appletalk/sysctl_net_atalk.c.

Project: linux
File: atalk_proc.c

	__acquires(atalk_interfaces_lock)
{
	loff_t l = *pos;

	read_lock_bh(&atalk_interfaces_lock);
	return l ? atalk_get_interface_idx(--l) : SEQ_START_TOKEN;
}

Project: linux
File: atalk_proc.c

void atalk_proc_exit(void)
{
	remove_proc_subtree("atalk", init_net.proc_net);
}

Project: linux
File: atalk_proc.c

static int atalk_seq_route_show(struct seq_file *seq, void *v)
{
	struct atalk_route *rt;

	if (v == SEQ_START_TOKEN) {
		seq_puts(seq, "Target        Router  Flags Dev\n");
		goto out;
	}

	if (atrtr_default.dev) {
		rt = &atrtr_default;
		seq_printf(seq, "Default     %04X:%02X  %-4d  %s\n",
			       ntohs(rt->gateway.s_net), rt->gateway.s_node,
			       rt->flags, rt->dev->name);
	}

	rt = v;
	seq_printf(seq, "%04X:%02X     %04X:%02X  %-4d  %s\n",
		   ntohs(rt->target.s_net), rt->target.s_node,
		   ntohs(rt->gateway.s_net), rt->gateway.s_node,
		   rt->flags, rt->dev->name);
out:
	return 0;
}

Project: linux
File: sysctl_net_atalk.c

int __init atalk_register_sysctl(void)
{
	atalk_table_header = register_net_sysctl(&init_net, "net/appletalk", atalk_table);
	if (!atalk_table_header)
		return -ENOMEM;
	return 0;
}

Project: linux
File: atalk_proc.c

	__releases(atalk_sockets_lock)
{
	read_unlock_bh(&atalk_sockets_lock);
}

Project: linux
File: atalk_proc.c

static void *atalk_seq_interface_next(struct seq_file *seq, void *v, loff_t *pos)
{
	struct atalk_iface *i;

	++*pos;
	if (v == SEQ_START_TOKEN) {
		i = NULL;
		if (atalk_interfaces)
			i = atalk_interfaces;
		goto out;
	}
	i = v;
	i = i->next;
out:
	return i;
}

Project: linux
File: atalk_proc.c

static int atalk_seq_socket_show(struct seq_file *seq, void *v)
{
	struct sock *s;
	struct atalk_sock *at;

	if (v == SEQ_START_TOKEN) {
		seq_printf(seq, "Type Local_addr  Remote_addr Tx_queue "
				"Rx_queue St UID\n");
		goto out;
	}

	s = sk_entry(v);
	at = at_sk(s);

	seq_printf(seq, "%02X   %04X:%02X:%02X  %04X:%02X:%02X  %08X:%08X "
			"%02X %u\n",
		   s->sk_type, ntohs(at->src_net), at->src_node, at->src_port,
		   ntohs(at->dest_net), at->dest_node, at->dest_port,
		   sk_wmem_alloc_get(s),
		   sk_rmem_alloc_get(s),
		   s->sk_state,
		   from_kuid_munged(seq_user_ns(seq), sock_i_uid(s)));
out:
	return 0;
}

Project: linux
File: atalk_proc.c

static int atalk_seq_interface_show(struct seq_file *seq, void *v)
{
	struct atalk_iface *iface;

	if (v == SEQ_START_TOKEN) {
		seq_puts(seq, "Interface        Address   Networks  "
			      "Status\n");
		goto out;
	}

	iface = v;
	seq_printf(seq, "%-16s %04X:%02X  %04X-%04X  %d\n",
		   iface->dev->name, ntohs(iface->address.s_net),
		   iface->address.s_node, ntohs(iface->nets.nr_firstnet),
		   ntohs(iface->nets.nr_lastnet), iface->status);
out:
	return 0;
}

Project: linux
File: atalk_proc.c

	__acquires(atalk_sockets_lock)
{
	read_lock_bh(&atalk_sockets_lock);
	return seq_hlist_start_head(&atalk_sockets, *pos);
}

Project: linux
File: atalk_proc.c

int __init atalk_proc_init(void)
{
	if (!proc_mkdir("atalk", init_net.proc_net))
		return -ENOMEM;

	if (!proc_create_seq("atalk/interface", 0444, init_net.proc_net,
			    &atalk_seq_interface_ops))
		goto out;

	if (!proc_create_seq("atalk/route", 0444, init_net.proc_net,
			    &atalk_seq_route_ops))
		goto out;

	if (!proc_create_seq("atalk/socket", 0444, init_net.proc_net,
			    &atalk_seq_socket_ops))
		goto out;

	if (!proc_create_seq_private("atalk/arp", 0444, init_net.proc_net,
				     &aarp_seq_ops,
				     sizeof(struct aarp_iter_state), NULL))
		goto out;

out:
	remove_proc_subtree("atalk", init_net.proc_net);
	return -ENOMEM;
}

Project: linux
File: atalk_proc.c

	__releases(atalk_interfaces_lock)
{
	read_unlock_bh(&atalk_interfaces_lock);
}

Project: linux
File: sysctl_net_atalk.c

void atalk_unregister_sysctl(void)
{
	unregister_net_sysctl_table(atalk_table_header);
}

Project: linux
File: atalk_proc.c

	__releases(atalk_routes_lock)
{
	read_unlock_bh(&atalk_routes_lock);
}

Project: linux
File: atalk_proc.c

static void *atalk_seq_socket_next(struct seq_file *seq, void *v, loff_t *pos)
{
	return seq_hlist_next(v, &atalk_sockets, pos);
}

Project: linux
File: atalk_proc.c

static __inline__ struct atalk_route *atalk_get_route_idx(loff_t pos)
{
	struct atalk_route *r;

	for (r = atalk_routes; pos && r; r = r->next)
		--pos;

	return r;
}

Project: linux
File: atalk_proc.c

	__acquires(atalk_routes_lock)
{
	loff_t l = *pos;

	read_lock_bh(&atalk_routes_lock);
	return l ? atalk_get_route_idx(--l) : SEQ_START_TOKEN;
}

Project: linux
File: atalk_proc.c

static __inline__ struct atalk_iface *atalk_get_interface_idx(loff_t pos)
{
	struct atalk_iface *i;

	for (i = atalk_interfaces; pos && i; i = i->next)
		--pos;

	return i;
}

Project: linux
File: atalk_proc.c

static void *atalk_seq_route_next(struct seq_file *seq, void *v, loff_t *pos)
{
	struct atalk_route *r;

	++*pos;
	if (v == SEQ_START_TOKEN) {
		r = NULL;
		if (atalk_routes)
			r = atalk_routes;
		goto out;
	}
	r = v;
	r = r->next;
out:
	return r;
}