CVE-2022-49372 — tcp: tcp_rtx_synack() can be called from process context

Affected: Linux

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:

0) Kernel built with CONFIG_DEBUG_PREEMPT=y

1) A new passive FastOpen TCP socket is created. This FO socket waits for an ACK coming from client to be a complete ESTABLISHED one. 2) A socket operation on this socket goes through lock_sock() release_sock() dance. 3) While the socket is owned by the user in step 2), a retransmit of the SYN is received and stored in socket backlog. 4) At release_sock() time, the socket backlog is processed while in process context. 5) A SYNACK packet is cooked in response of the SYN retransmit. 6) -> 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…

RHSA-2023:2458 — Red Hat Security Advisory: kernel security, bug fix, and enhancement update

hw: cpu: AMD CPUs may transiently execute beyond unconditional direct branch kernel: ext4: kernel bug in ext4_write_inline_data_end() kernel: malicious data for FBIOPUT_VSCREENINFO ioctl may cause OOB write memory kernel: hwmon: (mlxreg-fan) Return non-zero value when fan current state is enforced from sysfs kernel: mlxsw: thermal: Fix out-of-bounds memory accesses kernel: mlxsw: spectrum: Protect driver from buggy firmware kernel: net: stmmac: fix tc flower deletion for VLAN priority Rx steering kernel: can: etas_es58x: es58x_rx_err_msg(): fix memory leak in error path kernel: possible race condition in drivers/tty/tty_buffers.c kernel: KVM: NULL pointer dereference in kvm_mmu_invpcid_gva kernel: use-after-free in free_pipe_info() could lead to privilege escalation kernel: KVM: nVMX: missing IBPB when exiting from nested guest can lead to Spectre v2 attacks kernel: netfilter: nf_conntrack_irc message handling issue kernel: race condition in xfrm_probe_algs can lead to OOB read/write kernel: out-of-bounds read in fib_nh_match of the file net/ipv4/fib_semantics.c kernel: race condition in hugetlb_no_page() in mm/hugetlb.c kernel: memory leak in ipv6_renew_options() kernel: data races around icsk->icsk_af_ops in do_ipv6_setsockopt kernel: data races around sk->sk_prot kernel: memory leak in l2cap_recv_acldata of the file net/bluetooth/l2cap_core.c kernel: denial of service in follow_page_pte in mm/gup.c due to poisoned pte entry kernel: use-after-free after failed devlink relo…

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CVE-2022-49372 — tcp: tcp_rtx_synack() can be called from process context

RHSA-2023:2458 — Red Hat Security Advisory: kernel security, bug fix, and enhancement update