[PATCH] mac802154: fix interface deletion

[PATCH] mac802154: fix interface deletion

[Dmitry Antipov]

Syzbot has reported the following BUG:
kernel BUG at lib/list_debug.c:58!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 0 UID: 0 PID: 6277 Comm: syz-executor157 Not tainted 6.12.0-rc6-syzkaller-00005-g557329bcecc2 #0
Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
RIP: 0010:__list_del_entry_valid_or_report+0xf4/0x140 lib/list_debug.c:56
Code: e8 a1 7e 00 07 90 0f 0b 48 c7 c7 e0 37 60 8c 4c 89 fe e8 8f 7e 00 07 90 0f 0b 48 c7 c7 40 38 60 8c 4c 89 fe e8 7d 7e 00 07 90 <0f> 0b 48 c7 c7 a0 38 60 8c 4c 89 fe e8 6b 7e 00 07 90 0f 0b 48 c7
RSP: 0018:ffffc9000490f3d0 EFLAGS: 00010246
RAX: 000000000000004e RBX: dead000000000122 RCX: d211eee56bb28d00
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffff88805b278dd8 R08: ffffffff8174a12c R09: 1ffffffff2852f0d
R10: dffffc0000000000 R11: fffffbfff2852f0e R12: dffffc0000000000
R13: dffffc0000000000 R14: dead000000000100 R15: ffff88805b278cc0
FS:  0000555572f94380(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000056262e4a3000 CR3: 0000000078496000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __list_del_entry_valid include/linux/list.h:124 [inline]
 __list_del_entry include/linux/list.h:215 [inline]
 list_del_rcu include/linux/rculist.h:157 [inline]
 ieee802154_if_remove+0x86/0x1e0 net/mac802154/iface.c:687
 rdev_del_virtual_intf_deprecated net/ieee802154/rdev-ops.h:24 [inline]
 ieee802154_del_iface+0x2c0/0x5c0 net/ieee802154/nl-phy.c:323
 genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
 genl_rcv_msg+0xb14/0xec0 net/netlink/genetlink.c:1210
 netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2551
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
 netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1357
 netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901
 sock_sendmsg_nosec net/socket.c:729 [inline]
 __sock_sendmsg+0x221/0x270 net/socket.c:744
 ____sys_sendmsg+0x52a/0x7e0 net/socket.c:2607
 ___sys_sendmsg net/socket.c:2661 [inline]
 __sys_sendmsg+0x292/0x380 net/socket.c:2690
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd094c32309
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 71 19 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffec50063a8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fd094c32309
RDX: 0000000004000000 RSI: 0000000020000b00 RDI: 0000000000000004
RBP: 00000000000f4240 R08: 0000000000000000 R09: 00000000000000a0
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000000161b7
R13: 00007ffec50063bc R14: 00007ffec50063d0 R15: 00007ffec50063c0
 </TASK>

Since 'ieee802154_remove_interfaces()' and 'ieee802154_if_remove()' may try
to process the same 'struct ieee802154_sub_if_data' object concurrently,
there are two problems:

1) list of 'struct ieee802154_sub_if_data' objects linked via 'interfaces'
   field of 'struct ieee802154_local' should remain consistent;
2) 'unregister_netdevice()' should not be called for the same
   'struct net_device' concurrently.

IIUC RCU can guarantee 1) but not 2), so discard RCU quirks and prefer
explicit SDATA_STATE_REMOVED flag used via atomic and fully-ordered
'test_and_set_bit()' to mark 'struct ieee802154_sub_if_data' instance
which has entered the reclamation.

Reported-by: syzbot+985f827280dc3a6e7e92@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=985f827280dc3a6e7e92
Fixes: b210b18747cb ("mac802154: move interface del handling in iface")
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
---
 net/mac802154/ieee802154_i.h |  6 +++---
 net/mac802154/iface.c        | 10 +++++++---
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/net/mac802154/ieee802154_i.h b/net/mac802154/ieee802154_i.h
index 08dd521a51a5..7afcea3447c1 100644
--- a/net/mac802154/ieee802154_i.h
+++ b/net/mac802154/ieee802154_i.h
@@ -40,9 +40,8 @@ struct ieee802154_local {
 	int open_count;
 
 	/* As in mac80211 slaves list is modified:
-	 * 1) under the RTNL
-	 * 2) protected by slaves_mtx;
-	 * 3) in an RCU manner
+	 * 1) under the RTNL;
+	 * 2) protected by iflist_mtx.
 	 *
 	 * So atomic readers can use any of this protection methods.
 	 */
@@ -101,6 +100,7 @@ enum {
 
 enum ieee802154_sdata_state_bits {
 	SDATA_STATE_RUNNING,
+	SDATA_STATE_REMOVED,
 };
 
 /* Slave interface definition.
diff --git a/net/mac802154/iface.c b/net/mac802154/iface.c
index c0e2da5072be..700c80e94bb2 100644
--- a/net/mac802154/iface.c
+++ b/net/mac802154/iface.c
@@ -669,7 +669,7 @@ ieee802154_if_add(struct ieee802154_local *local, const char *name,
 		goto err;
 
 	mutex_lock(&local->iflist_mtx);
-	list_add_tail_rcu(&sdata->list, &local->interfaces);
+	list_add_tail(&sdata->list, &local->interfaces);
 	mutex_unlock(&local->iflist_mtx);
 
 	return ndev;
@@ -683,11 +683,13 @@ void ieee802154_if_remove(struct ieee802154_sub_if_data *sdata)
 {
 	ASSERT_RTNL();
 
+	if (test_and_set_bit(SDATA_STATE_REMOVED, &sdata->state))
+		return;
+
 	mutex_lock(&sdata->local->iflist_mtx);
-	list_del_rcu(&sdata->list);
+	list_del(&sdata->list);
 	mutex_unlock(&sdata->local->iflist_mtx);
 
-	synchronize_rcu();
 	unregister_netdevice(sdata->dev);
 }
 
@@ -697,6 +699,8 @@ void ieee802154_remove_interfaces(struct ieee802154_local *local)
 
 	mutex_lock(&local->iflist_mtx);
 	list_for_each_entry_safe(sdata, tmp, &local->interfaces, list) {
+		if (test_and_set_bit(SDATA_STATE_REMOVED, &sdata->state))
+			continue;
 		list_del(&sdata->list);
 
 		unregister_netdevice(sdata->dev);
-- 
2.47.0

Re: [PATCH] mac802154: fix interface deletion

[Miquel Raynal]

Hello Dmitry,

> --- a/net/mac802154/iface.c
> +++ b/net/mac802154/iface.c
> @@ -669,7 +669,7 @@ ieee802154_if_add(struct ieee802154_local *local, const char *name,
>  		goto err;
>  
>  	mutex_lock(&local->iflist_mtx);
> -	list_add_tail_rcu(&sdata->list, &local->interfaces);
> +	list_add_tail(&sdata->list, &local->interfaces);
>  	mutex_unlock(&local->iflist_mtx);
>  
>  	return ndev;
> @@ -683,11 +683,13 @@ void ieee802154_if_remove(struct ieee802154_sub_if_data *sdata)
>  {
>  	ASSERT_RTNL();
>  
> +	if (test_and_set_bit(SDATA_STATE_REMOVED, &sdata->state))
> +		return;
> +
>  	mutex_lock(&sdata->local->iflist_mtx);
> -	list_del_rcu(&sdata->list);
> +	list_del(&sdata->list);
>  	mutex_unlock(&sdata->local->iflist_mtx);
>  
> -	synchronize_rcu();
>  	unregister_netdevice(sdata->dev);
>  }
>  
> @@ -697,6 +699,8 @@ void ieee802154_remove_interfaces(struct ieee802154_local *local)
>  
>  	mutex_lock(&local->iflist_mtx);
>  	list_for_each_entry_safe(sdata, tmp, &local->interfaces, list) {
> +		if (test_and_set_bit(SDATA_STATE_REMOVED, &sdata->state))
> +			continue;
>  		list_del(&sdata->list);

Why not just enclose this list_del() within a mutex_lock(iflist_mtx)
like the others? Would probably make more sense and prevent the use of
yet another protection mechanism? Is there anything preventing the use
of this mutex here?

Thanks,
Miquèl

Re: [PATCH] mac802154: fix interface deletion

[Dmitry Antipov]

On 11/11/24 10:41 PM, Miquel Raynal wrote:

> Why not just enclose this list_del() within a mutex_lock(iflist_mtx)
> like the others? Would probably make more sense and prevent the use of
> yet another protection mechanism? Is there anything preventing the use
> of this mutex here?

IIUC this will not work because 'ieee802154_if_remove()' may be called for
'sdata' which was previously removed via 'ieee802154_remove_interfaces()'.
After the latter, 'sdata->list' is undefined (or poisoned if CONFIG_DEBUG_LIST
is enabled), so re-entering 'list_del(&sdata->list)' in the former is a bug.

Dmitry

Re: [PATCH] mac802154: fix interface deletion

[Dmitry Antipov]

On 11/11/24 10:41 PM, Miquel Raynal wrote:

> Why not just enclose this list_del() within a mutex_lock(iflist_mtx)
> like the others? Would probably make more sense and prevent the use of
> yet another protection mechanism? Is there anything preventing the use
> of this mutex here?

Moreover, if we manage interfaces list with RCU and device status with
an extra status bit, do we need 'iflist_mtx' at all? I've tried this
in https://syzkaller.appspot.com/text?tag=Patch&x=17b1f4e8580000 and
it looks good.

Dmitry