CVE-2026-80984: net/smc: do not dereference an unset send buffer on the SMC-D teardown path

CVE-2026-80984: net/smc: do not dereference an unset send buffer on the SMC-D teardown path

[Greg Kroah-Hartman]

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

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

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

net/smc: do not dereference an unset send buffer on the SMC-D teardown path

smc_close_stream_wait() calls smc_tx_prepared_sends() from inside its
sk_wait_event() condition, and sk_wait_event() evaluates that condition
once with the socket lock released. smcd_buf_detach() clears
conn->sndbuf_desc from smc_conn_kill() under lock_sock(), so a link group
terminating while a socket waits there leaves the helper dereferencing
NULL, faulting out of close(). SIOCOUTQ reads the field by hand, and
smc_close_cancel_work() drops the lock across two cancel_*_sync() calls.

Sample the pointer once in the helper, report nothing prepared while it is
unset, and bound the ioctl the same way. The receive tasklet dereferences
the field directly in smc_cdc_msg_recv_action(), not through this helper;
1/2 is what keeps it from running that late.

The Linux kernel CVE team has assigned CVE-2026-80984 to this issue.


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

	Issue introduced in 6.10 with commit ae2be35cbed2c8385e890147ea321a3fcc3ca5fa and fixed in 6.12.109 with commit e3fcff8d22a6c9540748846cd800443a643553a6
	Issue introduced in 6.10 with commit ae2be35cbed2c8385e890147ea321a3fcc3ca5fa and fixed in 6.18.50 with commit f950e1b1f0aad334f9a9ee552c4dd5b794ebdd45
	Issue introduced in 6.10 with commit ae2be35cbed2c8385e890147ea321a3fcc3ca5fa and fixed in 7.2.4 with commit f517cf02033801a28f98d86ca613a3533cf066b3
	Issue introduced in 6.10 with commit ae2be35cbed2c8385e890147ea321a3fcc3ca5fa and fixed in 7.3-rc1 with commit b395dd319cea422239cb45b998fb38d7e373af87
	Issue introduced in 6.6.66 with commit 21f6f41e82e59740e26e06e77bdf58dc7f6f08dd

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-2026-80984
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/smc/af_smc.c
	net/smc/smc_tx.h


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/e3fcff8d22a6c9540748846cd800443a643553a6
	https://git.kernel.org/stable/c/f950e1b1f0aad334f9a9ee552c4dd5b794ebdd45
	https://git.kernel.org/stable/c/f517cf02033801a28f98d86ca613a3533cf066b3
	https://git.kernel.org/stable/c/b395dd319cea422239cb45b998fb38d7e373af87