CVE-2024-26635

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> llc: Drop support for ETH_P_TR_802_2.<br /> <br /> syzbot reported an uninit-value bug below. [0]<br /> <br /> llc supports ETH_P_802_2 (0x0004) and used to support ETH_P_TR_802_2<br /> (0x0011), and syzbot abused the latter to trigger the bug.<br /> <br /> write$tun(r0, &amp;(0x7f0000000040)={@val={0x0, 0x11}, @val, @mpls={[], @llc={@snap={0xaa, 0x1, &amp;#39;)&amp;#39;, "90e5dd"}}}}, 0x16)<br /> <br /> llc_conn_handler() initialises local variables {saddr,daddr}.mac<br /> based on skb in llc_pdu_decode_sa()/llc_pdu_decode_da() and passes<br /> them to __llc_lookup().<br /> <br /> However, the initialisation is done only when skb-&gt;protocol is<br /> htons(ETH_P_802_2), otherwise, __llc_lookup_established() and<br /> __llc_lookup_listener() will read garbage.<br /> <br /> The missing initialisation existed prior to commit 211ed865108e<br /> ("net: delete all instances of special processing for token ring").<br /> <br /> It removed the part to kick out the token ring stuff but forgot to<br /> close the door allowing ETH_P_TR_802_2 packets to sneak into llc_rcv().<br /> <br /> Let&amp;#39;s remove llc_tr_packet_type and complete the deprecation.<br /> <br /> [0]:<br /> BUG: KMSAN: uninit-value in __llc_lookup_established+0xe9d/0xf90<br /> __llc_lookup_established+0xe9d/0xf90<br /> __llc_lookup net/llc/llc_conn.c:611 [inline]<br /> llc_conn_handler+0x4bd/0x1360 net/llc/llc_conn.c:791<br /> llc_rcv+0xfbb/0x14a0 net/llc/llc_input.c:206<br /> __netif_receive_skb_one_core net/core/dev.c:5527 [inline]<br /> __netif_receive_skb+0x1a6/0x5a0 net/core/dev.c:5641<br /> netif_receive_skb_internal net/core/dev.c:5727 [inline]<br /> netif_receive_skb+0x58/0x660 net/core/dev.c:5786<br /> tun_rx_batched+0x3ee/0x980 drivers/net/tun.c:1555<br /> tun_get_user+0x53af/0x66d0 drivers/net/tun.c:2002<br /> tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048<br /> call_write_iter include/linux/fs.h:2020 [inline]<br /> new_sync_write fs/read_write.c:491 [inline]<br /> vfs_write+0x8ef/0x1490 fs/read_write.c:584<br /> ksys_write+0x20f/0x4c0 fs/read_write.c:637<br /> __do_sys_write fs/read_write.c:649 [inline]<br /> __se_sys_write fs/read_write.c:646 [inline]<br /> __x64_sys_write+0x93/0xd0 fs/read_write.c:646<br /> do_syscall_x64 arch/x86/entry/common.c:51 [inline]<br /> do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82<br /> entry_SYSCALL_64_after_hwframe+0x63/0x6b<br /> <br /> Local variable daddr created at:<br /> llc_conn_handler+0x53/0x1360 net/llc/llc_conn.c:783<br /> llc_rcv+0xfbb/0x14a0 net/llc/llc_input.c:206<br /> <br /> CPU: 1 PID: 5004 Comm: syz-executor994 Not tainted 6.6.0-syzkaller-14500-g1c41041124bd #0<br /> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023