{"id":"CVE-2022-49372","summary":"tcp: tcp_rtx_synack() can be called from process context","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: tcp_rtx_synack() can be called from process context\n\nLaurent reported the enclosed report [1]\n\nThis bug triggers with following coditions:\n\n0) Kernel built with CONFIG_DEBUG_PREEMPT=y\n\n1) A new passive FastOpen TCP socket is created.\n   This FO socket waits for an ACK coming from client to be a complete\n   ESTABLISHED one.\n2) A socket operation on this socket goes through lock_sock()\n   release_sock() dance.\n3) While the socket is owned by the user in step 2),\n   a retransmit of the SYN is received and stored in socket backlog.\n4) At release_sock() time, the socket backlog is processed while\n   in process context.\n5) A SYNACK packet is cooked in response of the SYN retransmit.\n6) -\u003e tcp_rtx_synack() is called in process context.\n\nBefore blamed commit, tcp_rtx_synack() was always called from BH handler,\nfrom a timer handler.\n\nFix this by using TCP_INC_STATS() & NET_INC_STATS()\nwhich do not assume caller is in non preemptible context.\n\n[1]\nBUG: using __this_cpu_add() in preemptible [00000000] code: epollpep/2180\ncaller is tcp_rtx_synack.part.0+0x36/0xc0\nCPU: 10 PID: 2180 Comm: epollpep Tainted: G           OE     5.16.0-0.bpo.4-amd64 #1  Debian 5.16.12-1~bpo11+1\nHardware name: Supermicro SYS-5039MC-H8TRF/X11SCD-F, BIOS 1.7 11/23/2021\nCall Trace:\n \u003cTASK\u003e\n dump_stack_lvl+0x48/0x5e\n check_preemption_disabled+0xde/0xe0\n tcp_rtx_synack.part.0+0x36/0xc0\n tcp_rtx_synack+0x8d/0xa0\n ? kmem_cache_alloc+0x2e0/0x3e0\n ? apparmor_file_alloc_security+0x3b/0x1f0\n inet_rtx_syn_ack+0x16/0x30\n tcp_check_req+0x367/0x610\n tcp_rcv_state_process+0x91/0xf60\n ? get_nohz_timer_target+0x18/0x1a0\n ? lock_timer_base+0x61/0x80\n ? preempt_count_add+0x68/0xa0\n tcp_v4_do_rcv+0xbd/0x270\n __release_sock+0x6d/0xb0\n release_sock+0x2b/0x90\n sock_setsockopt+0x138/0x1140\n ? __sys_getsockname+0x7e/0xc0\n ? aa_sk_perm+0x3e/0x1a0\n __sys_setsockopt+0x198/0x1e0\n __x64_sys_setsockopt+0x21/0x30\n do_syscall_64+0x38/0xc0\n entry_SYSCALL_64_after_hwframe+0x44/0xae","modified":"2026-04-02T08:27:31.744234Z","published":"2025-02-26T02:11:14.119Z","related":["SUSE-SU-2025:1293-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2022/49xxx/CVE-2022-49372.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0a0f7f84148445c9f02f226928803a870139d820"},{"type":"WEB","url":"https://git.kernel.org/stable/c/0a375c822497ed6ad6b5da0792a12a6f1af10c0b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3db889f883e65bbd3b1401279bfc1e9ed255c481"},{"type":"WEB","url":"https://git.kernel.org/stable/c/58bd38cbc961fd799842b7be8c5222310f04b908"},{"type":"WEB","url":"https://git.kernel.org/stable/c/88cd232146207ff1d41dededed5e77c0d4438113"},{"type":"WEB","url":"https://git.kernel.org/stable/c/bdc28a8fb43cc476e33b11519235adb816ce00e8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c348b0f8d035fc4bdc040796889beec7218bd1b8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d05c2fdf8e10528bb6751bd95243e862d5402a9b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d8e1bc6029acac796293310aacef7b7336f35b6a"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2022/49xxx/CVE-2022-49372.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2022-49372"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"168a8f58059a22feb9e9a2dcc1b8053dbbbc12ef"},{"fixed":"3db889f883e65bbd3b1401279bfc1e9ed255c481"},{"fixed":"c348b0f8d035fc4bdc040796889beec7218bd1b8"},{"fixed":"58bd38cbc961fd799842b7be8c5222310f04b908"},{"fixed":"d05c2fdf8e10528bb6751bd95243e862d5402a9b"},{"fixed":"0a0f7f84148445c9f02f226928803a870139d820"},{"fixed":"88cd232146207ff1d41dededed5e77c0d4438113"},{"fixed":"bdc28a8fb43cc476e33b11519235adb816ce00e8"},{"fixed":"d8e1bc6029acac796293310aacef7b7336f35b6a"},{"fixed":"0a375c822497ed6ad6b5da0792a12a6f1af10c0b"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2022-49372.json"}}],"schema_version":"1.7.5"}