net/smc: fix socket refcount leak in smc_switch_conns()

Overview

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

net/smc: fix socket refcount leak in smc_switch_conns()

smc_switch_conns() takes a reference on the SMC socket before dropping lgr->conns_lock, so the connection stays alive while the CDC slot is fetched:

    sock_hold(&smc->sk);
    read_unlock_bh(&lgr->conns_lock);
    /* pre-fetch buffer outside of send_lock, might sleep */
    rc = smc_cdc_get_free_slot(conn, to_lnk, &wr_buf, NULL, &pend);
    if (rc)
            goto err_out;

The err_out label only drops the wr_tx link reference, so this early exit returns without the matching sock_put(). The second error exit is not affected, because sock_put() has already run by then.

A leaked sk_refcnt means the smc_sock is never destroyed. Its send and receive buffers stay allocated, and for a user socket the reference held on the network namespace is never released, so the netns can no longer be torn down.

smc_cdc_get_free_slot() fails when the target link goes down or when the connection has been killed while the switch is in progress. Both are reachable during the link failover this function implements, so the leak is triggered by the same hardware events that make smc_switch_conns() run in the first place.

Restructure so there is a single sock_put() covering both outcomes, instead of adding a second one to the error path.

Affected

• Linux >= 95f7f3e7dc6bd2e735cb5de11734ea2222b1e05a < a3378466704e0bbe93aef9769552dca7673a7eb6
• Linux >= 95f7f3e7dc6bd2e735cb5de11734ea2222b1e05a < e20227019d9da73f8fdf16f0951c2e188c84933f
• Linux >= 95f7f3e7dc6bd2e735cb5de11734ea2222b1e05a < 09d7a9e162ee1a269878c126aee3d7eff43e4130
• Linux >= 95f7f3e7dc6bd2e735cb5de11734ea2222b1e05a < 84dea0585f6b538ae895a8b1d025f4897737f3b1
• Linux >= 95f7f3e7dc6bd2e735cb5de11734ea2222b1e05a < d89dc1bd8845c669a700eee58c64ebd3cc1b6d2d
• Linux >= 95f7f3e7dc6bd2e735cb5de11734ea2222b1e05a < d9a879ac25958bdaecb669ce70e58f8e2ff170de
• Linux >= 95f7f3e7dc6bd2e735cb5de11734ea2222b1e05a < 719296c4aa8213d4ac8002e77d5956d436bc98d0
• Linux 99f19566b1c4d3dc4d934ee2ef43faadebb56d70
• Linux 0d9ddf515cde793841f738490037560fd6559c63
• Linux >= 5.10.90 < 5.11
• Linux >= 5.14.14 < 5.15
• Linux 5.15

Remediation

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

Vendor advisories

• Red Hat VEX · Low · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-10-17 · vex