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

Overview

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.

Affected

• Linux >= 21f6f41e82e59740e26e06e77bdf58dc7f6f08dd < ab26e12dd5d2f43d939fcf456933a816e81d2e51
• Linux >= ae2be35cbed2c8385e890147ea321a3fcc3ca5fa < e3fcff8d22a6c9540748846cd800443a643553a6
• Linux >= ae2be35cbed2c8385e890147ea321a3fcc3ca5fa < f950e1b1f0aad334f9a9ee552c4dd5b794ebdd45
• Linux >= ae2be35cbed2c8385e890147ea321a3fcc3ca5fa < f517cf02033801a28f98d86ca613a3533cf066b3
• Linux >= ae2be35cbed2c8385e890147ea321a3fcc3ca5fa < b395dd319cea422239cb45b998fb38d7e373af87
• Linux >= 6.6.66 < 6.6.157
• Linux 6.10

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Vendor advisories

• Red Hat VEX · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-09-14 · vex