[PATCH v2 0/2] appletalk: small cleanup and bugfix

[PATCH v2 0/2] appletalk: small cleanup and bugfix

[Yue Haibing]

From: YueHaibing <yuehaibing@huawei.com>

v2:
- Add cover letter log

This patch series mainly fix a use-after-free bug in atalk_proc_exit.
patch 1 use remove_proc_subtree helper to simplify atalk_proc fs code,
also some other cleanup.
patch 2 add proper error cleanup path in atalk_init to fix the issue, which
based on the patch 1 because of the change of atalk_proc_exit context.

YueHaibing (2):
  appletalk: use remove_proc_subtree to simplify procfs code
  appletalk: Fix use-after-free in atalk_proc_exit

 include/linux/atalk.h            |  2 +-
 net/appletalk/atalk_proc.c       | 58 +++++++++++++---------------------------
 net/appletalk/ddp.c              | 37 ++++++++++++++++++++-----
 net/appletalk/sysctl_net_atalk.c |  5 +++-
 4 files changed, 54 insertions(+), 48 deletions(-)

-- 
2.7.0

[PATCH v2 1/2] appletalk: use remove_proc_subtree to simplify procfs code

[Yue Haibing]

From: YueHaibing <yuehaibing@huawei.com>

Use remove_proc_subtree to remove the whole subtree
on cleanup.Also do some cleanup.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
---
 net/appletalk/atalk_proc.c | 56 ++++++++++++++--------------------------------
 1 file changed, 17 insertions(+), 39 deletions(-)

diff --git a/net/appletalk/atalk_proc.c b/net/appletalk/atalk_proc.c
index 8006295..bd8734e 100644
--- a/net/appletalk/atalk_proc.c
+++ b/net/appletalk/atalk_proc.c
@@ -210,56 +210,34 @@ static const struct seq_operations atalk_seq_socket_ops = {
 	.show   = atalk_seq_socket_show,
 };
 
-static struct proc_dir_entry *atalk_proc_dir;
-
 int __init atalk_proc_init(void)
 {
-	struct proc_dir_entry *p;
-	int rc = -ENOMEM;
+	if (!proc_mkdir("atalk", init_net.proc_net))
+		return -ENOMEM;
 
-	atalk_proc_dir = proc_mkdir("atalk", init_net.proc_net);
-	if (!atalk_proc_dir)
+	if (!proc_create_seq("atalk/interface", 0444, init_net.proc_net,
+			    &atalk_seq_interface_ops))
 		goto out;
 
-	p = proc_create_seq("interface", 0444, atalk_proc_dir,
-			&atalk_seq_interface_ops);
-	if (!p)
-		goto out_interface;
-
-	p = proc_create_seq("route", 0444, atalk_proc_dir,
-			&atalk_seq_route_ops);
-	if (!p)
-		goto out_route;
+	if (!proc_create_seq("atalk/route", 0444, init_net.proc_net,
+			    &atalk_seq_route_ops))
+		goto out;
 
-	p = proc_create_seq("socket", 0444, atalk_proc_dir,
-			&atalk_seq_socket_ops);
-	if (!p)
-		goto out_socket;
+	if (!proc_create_seq("atalk/socket", 0444, init_net.proc_net,
+			    &atalk_seq_socket_ops))
+		goto out;
 
-	p = proc_create_seq_private("arp", 0444, atalk_proc_dir, &aarp_seq_ops,
-			sizeof(struct aarp_iter_state), NULL);
-	if (!p)
-		goto out_arp;
+	if (!proc_create_seq_private("atalk/arp", 0444, init_net.proc_net,
+				     &aarp_seq_ops,
+				     sizeof(struct aarp_iter_state), NULL))
+		goto out;
 
-	rc = 0;
 out:
-	return rc;
-out_arp:
-	remove_proc_entry("socket", atalk_proc_dir);
-out_socket:
-	remove_proc_entry("route", atalk_proc_dir);
-out_route:
-	remove_proc_entry("interface", atalk_proc_dir);
-out_interface:
-	remove_proc_entry("atalk", init_net.proc_net);
-	goto out;
+	remove_proc_subtree("atalk", init_net.proc_net);
+	return -ENOMEM;
 }
 
 void __exit atalk_proc_exit(void)
 {
-	remove_proc_entry("interface", atalk_proc_dir);
-	remove_proc_entry("route", atalk_proc_dir);
-	remove_proc_entry("socket", atalk_proc_dir);
-	remove_proc_entry("arp", atalk_proc_dir);
-	remove_proc_entry("atalk", init_net.proc_net);
+	remove_proc_subtree("atalk", init_net.proc_net);
 }
-- 
2.7.0

[PATCH v2 2/2] appletalk: Fix use-after-free in atalk_proc_exit

[Yue Haibing]

From: YueHaibing <yuehaibing@huawei.com>

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>
---
 include/linux/atalk.h            |  2 +-
 net/appletalk/atalk_proc.c       |  2 +-
 net/appletalk/ddp.c              | 37 +++++++++++++++++++++++++++++++------
 net/appletalk/sysctl_net_atalk.c |  5 ++++-
 4 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/include/linux/atalk.h b/include/linux/atalk.h
index 23f8055..5a90f28 100644
--- a/include/linux/atalk.h
+++ b/include/linux/atalk.h
@@ -158,7 +158,7 @@ extern int sysctl_aarp_retransmit_limit;
 extern int sysctl_aarp_resolve_time;
 
 #ifdef CONFIG_SYSCTL
-extern void atalk_register_sysctl(void);
+extern int atalk_register_sysctl(void);
 extern void atalk_unregister_sysctl(void);
 #else
 #define atalk_register_sysctl()		do { } while(0)
diff --git a/net/appletalk/atalk_proc.c b/net/appletalk/atalk_proc.c
index bd8734e..77f203f 100644
--- a/net/appletalk/atalk_proc.c
+++ b/net/appletalk/atalk_proc.c
@@ -237,7 +237,7 @@ int __init atalk_proc_init(void)
 	return -ENOMEM;
 }
 
-void __exit atalk_proc_exit(void)
+void atalk_proc_exit(void)
 {
 	remove_proc_subtree("atalk", init_net.proc_net);
 }
diff --git a/net/appletalk/ddp.c b/net/appletalk/ddp.c
index 9b6bc5a..795fbc6 100644
--- a/net/appletalk/ddp.c
+++ b/net/appletalk/ddp.c
@@ -1910,12 +1910,16 @@ static const char atalk_err_snap[] __initconst =
 /* Called by proto.c on kernel start up */
 static int __init atalk_init(void)
 {
-	int rc = proto_register(&ddp_proto, 0);
+	int rc;
 
-	if (rc != 0)
+	rc = proto_register(&ddp_proto, 0);
+	if (rc)
 		goto out;
 
-	(void)sock_register(&atalk_family_ops);
+	rc = sock_register(&atalk_family_ops);
+	if (rc)
+		goto out_proto;
+
 	ddp_dl = register_snap_client(ddp_snap_id, atalk_rcv);
 	if (!ddp_dl)
 		printk(atalk_err_snap);
@@ -1923,12 +1927,33 @@ static int __init atalk_init(void)
 	dev_add_pack(&ltalk_packet_type);
 	dev_add_pack(&ppptalk_packet_type);
 
-	register_netdevice_notifier(&ddp_notifier);
+	rc = register_netdevice_notifier(&ddp_notifier);
+	if (rc)
+		goto out_sock;
+
 	aarp_proto_init();
-	atalk_proc_init();
-	atalk_register_sysctl();
+	rc = atalk_proc_init();
+	if (rc)
+		goto out_aarp;
+
+	rc = atalk_register_sysctl();
+	if (rc)
+		goto out_proc;
 out:
 	return rc;
+out_proc:
+	atalk_proc_exit();
+out_aarp:
+	aarp_cleanup_module();
+	unregister_netdevice_notifier(&ddp_notifier);
+out_sock:
+	dev_remove_pack(&ppptalk_packet_type);
+	dev_remove_pack(&ltalk_packet_type);
+	unregister_snap_client(ddp_dl);
+	sock_unregister(PF_APPLETALK);
+out_proto:
+	proto_unregister(&ddp_proto);
+	goto out;
 }
 module_init(atalk_init);
 
diff --git a/net/appletalk/sysctl_net_atalk.c b/net/appletalk/sysctl_net_atalk.c
index c744a85..d945b7c 100644
--- a/net/appletalk/sysctl_net_atalk.c
+++ b/net/appletalk/sysctl_net_atalk.c
@@ -45,9 +45,12 @@ static struct ctl_table atalk_table[] = {
 
 static struct ctl_table_header *atalk_table_header;
 
-void atalk_register_sysctl(void)
+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;
 }
 
 void atalk_unregister_sysctl(void)
-- 
2.7.0

Re: [PATCH v2 0/2] appletalk: small cleanup and bugfix

[David Miller]

From: Yue Haibing <yuehaibing@huawei.com>
Date: Fri, 1 Mar 2019 10:57:55 +0800

> From: YueHaibing <yuehaibing@huawei.com>
> 
> v2:
> - Add cover letter log
> 
> This patch series mainly fix a use-after-free bug in atalk_proc_exit.
> patch 1 use remove_proc_subtree helper to simplify atalk_proc fs code,
> also some other cleanup.
> patch 2 add proper error cleanup path in atalk_init to fix the issue, which
> based on the patch 1 because of the change of atalk_proc_exit context.

Series applied, thanks.