CVE-2026-43411: tipc: fix divide-by-zero in tipc_sk_filter_connect()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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

tipc: fix divide-by-zero in tipc_sk_filter_connect()

A user can set conn_timeout to any value via
setsockopt(TIPC_CONN_TIMEOUT), including values less than 4.  When a
SYN is rejected with TIPC_ERR_OVERLOAD and the retry path in
tipc_sk_filter_connect() executes:

    delay %= (tsk->conn_timeout / 4);

If conn_timeout is in the range [0, 3], the integer division yields 0,
and the modulo operation triggers a divide-by-zero exception, causing a
kernel oops/panic.

Fix this by clamping conn_timeout to a minimum of 4 at the point of use
in tipc_sk_filter_connect().

Oops: divide error: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 119 Comm: poc-F144 Not tainted 7.0.0-rc2+
RIP: 0010:tipc_sk_filter_rcv (net/tipc/socket.c:2236 net/tipc/socket.c:2362)
Call Trace:
 tipc_sk_backlog_rcv (include/linux/instrumented.h:82 include/linux/atomic/atomic-instrumented.h:32 include/net/sock.h:2357 net/tipc/socket.c:2406)
 __release_sock (include/net/sock.h:1185 net/core/sock.c:3213)
 release_sock (net/core/sock.c:3797)
 tipc_connect (net/tipc/socket.c:2570)
 __sys_connect (include/linux/file.h:62 include/linux/file.h:83 net/socket.c:2098)

The Linux kernel CVE team has assigned CVE-2026-43411 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 4.20 with commit 6787927475e52f6933e3affce365dabb2aa2fadf and fixed in 5.10.253 with commit 600feb0a66a98c6b7f6f02b5f3612e75f9b8540f
	Issue introduced in 4.20 with commit 6787927475e52f6933e3affce365dabb2aa2fadf and fixed in 5.15.203 with commit 3bc9998041076ee05d3f312a22cee6b2ca35527f
	Issue introduced in 4.20 with commit 6787927475e52f6933e3affce365dabb2aa2fadf and fixed in 6.1.167 with commit 579956f9f297eb1b6a5d24de313f3acccee1f9d5
	Issue introduced in 4.20 with commit 6787927475e52f6933e3affce365dabb2aa2fadf and fixed in 6.6.130 with commit a360d3815aae1f00dd71b7714a846482e85cc1f7
	Issue introduced in 4.20 with commit 6787927475e52f6933e3affce365dabb2aa2fadf and fixed in 6.12.78 with commit c2ebfbe63deb7bfd4dc2532bae62a7ed67713272
	Issue introduced in 4.20 with commit 6787927475e52f6933e3affce365dabb2aa2fadf and fixed in 6.18.19 with commit 2754e7b3d64748643df867d1ea6fec522914b635
	Issue introduced in 4.20 with commit 6787927475e52f6933e3affce365dabb2aa2fadf and fixed in 6.19.9 with commit 338c5edeb6ae3f12a4b84dff9d71f6f7f8c202c3
	Issue introduced in 4.20 with commit 6787927475e52f6933e3affce365dabb2aa2fadf and fixed in 7.0 with commit 6c5a9baa15de240e747263aba435a0951da8d8d2

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-43411
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/tipc/socket.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/600feb0a66a98c6b7f6f02b5f3612e75f9b8540f
	https://git.kernel.org/stable/c/3bc9998041076ee05d3f312a22cee6b2ca35527f
	https://git.kernel.org/stable/c/579956f9f297eb1b6a5d24de313f3acccee1f9d5
	https://git.kernel.org/stable/c/a360d3815aae1f00dd71b7714a846482e85cc1f7
	https://git.kernel.org/stable/c/c2ebfbe63deb7bfd4dc2532bae62a7ed67713272
	https://git.kernel.org/stable/c/2754e7b3d64748643df867d1ea6fec522914b635
	https://git.kernel.org/stable/c/338c5edeb6ae3f12a4b84dff9d71f6f7f8c202c3
	https://git.kernel.org/stable/c/6c5a9baa15de240e747263aba435a0951da8d8d2