[PATCH v4 net] tipc: fix null-ptr-deref when acquiring remote ip of ethernet bearer

[PATCH v4 net] tipc: fix null-ptr-deref when acquiring remote ip of ethernet bearer

[Haixia Qu]

The reproduction steps:
1. create a tun interface
2. enable l2 bearer
3. TIPC_NL_UDP_GET_REMOTEIP with media name set to tun

tipc: Started in network mode
tipc: Node identity 8af312d38a21, cluster identity 4711
tipc: Enabled bearer <eth:syz_tun>, priority 1
Oops: general protection fault
KASAN: null-ptr-deref in range
CPU: 1 UID: 1000 PID: 559 Comm: poc Not tainted 6.16.0-rc1+ #117 PREEMPT
Hardware name: QEMU Ubuntu 24.04 PC
RIP: 0010:tipc_udp_nl_dump_remoteip+0x4a4/0x8f0

the ub was in fact a struct dev.

when bid != 0 && skip_cnt != 0, bearer_list[bid] may be NULL or
other media when other thread changes it.

fix this by checking media_id.

Fixes: 832629ca5c313 ("tipc: add UDP remoteip dump to netlink API")
Signed-off-by: Haixia Qu <hxqu@hillstonenet.com>
---
v4:
  - make commit message more descriptive
v3: https://patchwork.kernel.org/project/netdevbpf/patch/20250616042901.12978-1-hxqu@hillstonenet.com/
  - add Fixes tag in commit message
  - add target tree net
---
 net/tipc/udp_media.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c
index 108a4cc2e001..258d6aa4f21a 100644
--- a/net/tipc/udp_media.c
+++ b/net/tipc/udp_media.c
@@ -489,7 +489,7 @@ int tipc_udp_nl_dump_remoteip(struct sk_buff *skb, struct netlink_callback *cb)
 
 		rtnl_lock();
 		b = tipc_bearer_find(net, bname);
-		if (!b) {
+		if (!b || b->bcast_addr.media_id != TIPC_MEDIA_TYPE_UDP) {
 			rtnl_unlock();
 			return -EINVAL;
 		}
@@ -500,7 +500,7 @@ int tipc_udp_nl_dump_remoteip(struct sk_buff *skb, struct netlink_callback *cb)
 
 		rtnl_lock();
 		b = rtnl_dereference(tn->bearer_list[bid]);
-		if (!b) {
+		if (!b || b->bcast_addr.media_id != TIPC_MEDIA_TYPE_UDP) {
 			rtnl_unlock();
 			return -EINVAL;
 		}
-- 
2.43.0

RE: [PATCH v4 net] tipc: fix null-ptr-deref when acquiring remote ip of ethernet bearer

[Tung Quang Nguyen]

>Subject: [PATCH v4 net] tipc: fix null-ptr-deref when acquiring remote ip of
>ethernet bearer
>
>The reproduction steps:
>1. create a tun interface
>2. enable l2 bearer
>3. TIPC_NL_UDP_GET_REMOTEIP with media name set to tun
>
>tipc: Started in network mode
>tipc: Node identity 8af312d38a21, cluster identity 4711
>tipc: Enabled bearer <eth:syz_tun>, priority 1
>Oops: general protection fault
>KASAN: null-ptr-deref in range
>CPU: 1 UID: 1000 PID: 559 Comm: poc Not tainted 6.16.0-rc1+ #117 PREEMPT
>Hardware name: QEMU Ubuntu 24.04 PC
>RIP: 0010:tipc_udp_nl_dump_remoteip+0x4a4/0x8f0
>
>the ub was in fact a struct dev.
>
>when bid != 0 && skip_cnt != 0, bearer_list[bid] may be NULL or other media
>when other thread changes it.
>
>fix this by checking media_id.
>
>Fixes: 832629ca5c313 ("tipc: add UDP remoteip dump to netlink API")
>Signed-off-by: Haixia Qu <hxqu@hillstonenet.com>
>---
>v4:
>  - make commit message more descriptive
>v3:
>https://patchwork.kernel.org/project/netdevbpf/patch/20250616042901.12978
>-1-hxqu@hillstonenet.com/
>  - add Fixes tag in commit message
>  - add target tree net
>---
> net/tipc/udp_media.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c index
>108a4cc2e001..258d6aa4f21a 100644
>--- a/net/tipc/udp_media.c
>+++ b/net/tipc/udp_media.c
>@@ -489,7 +489,7 @@ int tipc_udp_nl_dump_remoteip(struct sk_buff *skb,
>struct netlink_callback *cb)
>
> 		rtnl_lock();
> 		b = tipc_bearer_find(net, bname);
>-		if (!b) {
>+		if (!b || b->bcast_addr.media_id != TIPC_MEDIA_TYPE_UDP) {
> 			rtnl_unlock();
> 			return -EINVAL;
> 		}
>@@ -500,7 +500,7 @@ int tipc_udp_nl_dump_remoteip(struct sk_buff *skb,
>struct netlink_callback *cb)
>
> 		rtnl_lock();
> 		b = rtnl_dereference(tn->bearer_list[bid]);
>-		if (!b) {
>+		if (!b || b->bcast_addr.media_id != TIPC_MEDIA_TYPE_UDP) {
> 			rtnl_unlock();
> 			return -EINVAL;
> 		}
>--
>2.43.0
>
Reviewed-by: Tung Nguyen <tung.quang.nguyen@est.tech>

Re: [PATCH v4 net] tipc: fix null-ptr-deref when acquiring remote ip of ethernet bearer

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Tue, 17 Jun 2025 05:56:24 +0000 you wrote:
> The reproduction steps:
> 1. create a tun interface
> 2. enable l2 bearer
> 3. TIPC_NL_UDP_GET_REMOTEIP with media name set to tun
> 
> tipc: Started in network mode
> tipc: Node identity 8af312d38a21, cluster identity 4711
> tipc: Enabled bearer <eth:syz_tun>, priority 1
> Oops: general protection fault
> KASAN: null-ptr-deref in range
> CPU: 1 UID: 1000 PID: 559 Comm: poc Not tainted 6.16.0-rc1+ #117 PREEMPT
> Hardware name: QEMU Ubuntu 24.04 PC
> RIP: 0010:tipc_udp_nl_dump_remoteip+0x4a4/0x8f0
> 
> [...]

Here is the summary with links:
  - [v4,net] tipc: fix null-ptr-deref when acquiring remote ip of ethernet bearer
    https://git.kernel.org/netdev/net/c/f82727adcf29

You are awesome, thank you!
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