tipc: fix null-ptr-deref when acquiring remote ip of ethernet bearer

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: 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.

References

• https://git.kernel.org/stable/c/3998283e4c32c0fe69edd59b0876c193f50abce6
• https://git.kernel.org/stable/c/c2e17984752b9131061d1a2ca1199da2706337fd
• https://git.kernel.org/stable/c/8595350615f952fcf8bc861464a6bf6b1129af50
• https://git.kernel.org/stable/c/05d332ba075753d569d66333d62d60fff5f57ad8
• https://git.kernel.org/stable/c/d3dfe821dfe091c0045044343c8d86596d66e2cf
• https://git.kernel.org/stable/c/0d3d91c3500f0c480e016faa4e2259c588616e59
• https://git.kernel.org/stable/c/0f4a72fb266e48dbe928e1d936eab149e4ac3e1b
• https://git.kernel.org/stable/c/f82727adcf2992822e12198792af450a76ebd5ef