CVE-2022-49372

Summary

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

tcp: tcp_rtx_synack() can be called from process context

Laurent reported the enclosed report [1]

This bug triggers with following coditions:

  1. Kernel built with CONFIG_DEBUG_PREEMPT=y

  2. A new passive FastOpen TCP socket is created. This FO socket waits for an ACK coming from client to be a complete ESTABLISHED one.

  3. A socket operation on this socket goes through lock_sock() release_sock() dance.

  4. While the socket is owned by the user in step 2), a retransmit of the SYN is received and stored in socket backlog.

  5. At release_sock() time, the socket backlog is processed while in process context.

  6. A SYNACK packet is cooked in response of the SYN retransmit.

  7. -> tcp_rtx_synack() is called in process context.

Before blamed commit, tcp_rtx_synack() was always called from BH handler, from a timer handler.

Fix this by using TCP_INC_STATS() & NET_INC_STATS() which do not assume caller is in non preemptible context.

[1] BUG: using __this_cpu_add() in preemptible [00000000] code: epollpep/2180 caller is tcp_rtx_synack.part.0+0x36/0xc0 CPU: 10 PID: 2180 Comm: epollpep Tainted: G OE 5.16.0-0.bpo.4-amd64 #1 Debian 5.16.12-1~bpo11+1 Hardware name: Supermicro SYS-5039MC-H8TRF/X11SCD-F, BIOS 1.7 11/23/2021 Call Trace: <TASK> dump_stack_lvl+0x48/0x5e check_preemption_disabled+0xde/0xe0 tcp_rtx_synack.part.0+0x36/0xc0 tcp_rtx_synack+0x8d/0xa0 ? kmem_cache_alloc+0x2e0/0x3e0 ? apparmor_file_alloc_security+0x3b/0x1f0 inet_rtx_syn_ack+0x16/0x30 tcp_check_req+0x367/0x610 tcp_rcv_state_process+0x91/0xf60 ? get_nohz_timer_target+0x18/0x1a0 ? lock_timer_base+0x61/0x80 ? preempt_count_add+0x68/0xa0 tcp_v4_do_rcv+0xbd/0x270 __release_sock+0x6d/0xb0 release_sock+0x2b/0x90 sock_setsockopt+0x138/0x1140 ? __sys_getsockname+0x7e/0xc0 ? aa_sk_perm+0x3e/0x1a0 __sys_setsockopt+0x198/0x1e0 __x64_sys_setsockopt+0x21/0x30 do_syscall_64+0x38/0xc0 entry_SYSCALL_64_after_hwframe+0x44/0xae

Affected Software

VendorProductVersion RangeStatus
LinuxLinux168a8f58059a22feb9e9a2dcc1b8053dbbbc12ef < 3db889f883e65bbd3b1401279bfc1e9ed255c481affected
LinuxLinux168a8f58059a22feb9e9a2dcc1b8053dbbbc12ef < c348b0f8d035fc4bdc040796889beec7218bd1b8affected
LinuxLinux168a8f58059a22feb9e9a2dcc1b8053dbbbc12ef < 58bd38cbc961fd799842b7be8c5222310f04b908affected
LinuxLinux168a8f58059a22feb9e9a2dcc1b8053dbbbc12ef < d05c2fdf8e10528bb6751bd95243e862d5402a9baffected
LinuxLinux168a8f58059a22feb9e9a2dcc1b8053dbbbc12ef < 0a0f7f84148445c9f02f226928803a870139d820affected
LinuxLinux168a8f58059a22feb9e9a2dcc1b8053dbbbc12ef < 88cd232146207ff1d41dededed5e77c0d4438113affected
LinuxLinux168a8f58059a22feb9e9a2dcc1b8053dbbbc12ef < bdc28a8fb43cc476e33b11519235adb816ce00e8affected
LinuxLinux168a8f58059a22feb9e9a2dcc1b8053dbbbc12ef < d8e1bc6029acac796293310aacef7b7336f35b6aaffected
LinuxLinux168a8f58059a22feb9e9a2dcc1b8053dbbbc12ef < 0a375c822497ed6ad6b5da0792a12a6f1af10c0baffected
LinuxLinux3.7affected
LinuxLinux0 < 3.7unaffected
LinuxLinux4.9.318 <= 4.9.*unaffected
LinuxLinux4.14.283 <= 4.14.*unaffected
LinuxLinux4.19.247 <= 4.19.*unaffected
LinuxLinux5.4.198 <= 5.4.*unaffected
LinuxLinux5.10.122 <= 5.10.*unaffected
LinuxLinux5.15.47 <= 5.15.*unaffected
LinuxLinux5.17.15 <= 5.17.*unaffected
LinuxLinux5.18.4 <= 5.18.*unaffected
LinuxLinux5.19 <= *unaffected

Weaknesses

References