The diag dump walks the socket hash table under a read_lock and dereferences conn->lgr and conn->lnk. Four paths expose a window where a hashed socket has freed or partially freed conn/lgr/lnk state. First, smc_conn_abort() calls smc_conn_free() during early handshake aborts while the socket is still hashed in SMC_INIT, synchronously freeing the lgr on the smc_lgr_cleanup_early() path without holding the hash write_lock. A concurrent diag reader can load a non-NULL conn->lgr and dereference lgr->is_smcd after the kfree. Guard the conn/lgr/lnk blocks in __smc_diag_dump() for SMC_INIT and SMC_CLOSED sockets. As a side effect the diag_mode field is reported as SMC_DIAG_MODE_SMCR for SMC-D sockets still in SMC_INIT; smcss suppresses those rows before printing the mode string so there is no rendered regression. Use smp_load_acquire() / smp_store_release() on sk_state to order these checks on weakly ordered CPUs. Second, in smc_conn_kill() on SMC-D with dmb_nocopy, smcd_buf_detach() NULLs and frees conn->sndbuf_desc before the socket is unhashed. A concurrent diag reader entering the CONNINFO block can dereference the freed descriptor. Unhash the socket at the top of smc_conn_kill(), before smcd_buf_detach(). Third, in the terminal teardown branches of smc_close_active_abort() (PEERCLOSEWAIT and PROCESSABORT groups) and in smc_close_passive_work(), smc_conn_free() drops lgr and lnk references while the socket is still hashed. Unhash immediately before each smc_conn_free() call at those two sites. Fourth, smc_listen_out_err() sets sk_state = SMC_CLOSED with a plain store after smc_conn_abort() -> smc_conn_free() has already cleared alert_token_local under write_lock_bh(). On weakly ordered CPUs a concurrent diag reader using smp_load_acquire() on sk_state can observe SMC_CLOSED while the preceding store to alert_token_local has not yet become visible, causing it to dereference an lgr whose reference was already dropped. Use smp_store_release() to order the alert_token_local clear before the sk_state = SMC_CLOSED store. Additionally, in __smc_diag_dump(), use cached link->ibname instead of chasing link->smcibdev->ibdev->name to avoid racing with link clearing during SMC-R link failover. Fixes: f16a7dd5cf27 ("smc: netlink interface for SMC sockets") Fixes: 9dbe086c69b8 ("net/smc: fix invalid link access in dumping SMC-R connections") Fixes: ae2be35cbed2 ("net/smc: {at|de}tach sndbuf to peer DMB if supported") Cc: stable@vger.kernel.org Reviewed-by: Hidayath Khan Reviewed-by: Sidraya Jayagond Signed-off-by: Mahanta Jambigi --- Changes in v9: - af_smc.c: change plain store in smc_listen_out_err() to smp_store_release(&newsmcsk->sk_state, SMC_CLOSED) to order the preceding alert_token_local clear (done under write_lock_bh() inside smc_conn_free()) before the sk_state write; pairs with the smp_load_acquire() in __smc_diag_dump() to close a use-after-free on weakly ordered CPUs where a diag reader could observe SMC_CLOSED while conn->lgr still appeared live Changes in v8: - smc_diag.c: use smp_load_acquire(&sk->sk_state) to prevent speculative load reordering on weakly ordered CPUs (such as arm64) during handshake abort fallback - af_smc.c: pair with smp_store_release(&sk->sk_state, SMC_ACTIVE) when transitioning out of SMC_INIT - smc_diag.c: copy cached link->ibname instead of chasing link->smcibdev->ibdev->name to prevent NULL pointer dereference / UAF if __smcr_link_clear() zeroes the link during link failover Changes in v7: - no code changes; commit message only - document the SMC_CLOSED leg of the early-exit guard and the rationale that smcss already skips CLOSED sockets on the userspace side; add Fixes: ae2be35cbed2 for the smc_conn_kill() hunk since smcd_buf_detach() was introduced by that commit Changes in v6: - smc_diag.c: inline sk->sk_state != SMC_INIT into the else-if condition so conn->lgr->is_smcd is never loaded for SMC_INIT sockets; retain the SMC_INIT || SMC_CLOSED early-exit guard and out: label from v5 to defensively skip the CONNINFO/LGRINFO/DMBINFO blocks for sockets with no live connection - smc_close.c: remove the unconditional unhash from the top of smc_close_active_abort(); place it scoped immediately before each of the two smc_conn_free() calls in the PEERCLOSEWAIT and PROCESSABORT branches, and before smc_conn_free() in smc_close_passive_work(); this avoids prematurely hiding live SMC_ACTIVE/APPCLOSEWAIT sockets from smcss - smc_core.c: unhash at the top of smc_conn_kill(), before smcd_buf_detach(), so the socket is off the hash table before conn->sndbuf_desc is freed on the dmb_nocopy path Changes in v5: - guard conn/lgr/lnk blocks in __smc_diag_dump() with an (SMC_INIT || SMC_CLOSED) state check placed after the SMC_DIAG_FALLBACK nla_put; SMC_INIT can coexist with fallback (smc_sendmsg() MSG_FASTOPEN path), so the guard must not suppress the fallback reason Changes in v4: - dropped smc_conn_unhash() wrapper, conn->unhashed flag, and all changes to af_smc.c, smc.h, smc_core.c and smc_core.h; smc_unhash_sk() is already idempotent via sk_hashed(), so direct calls at the two teardown sites in smc_close.c are sufficient - dropped the __smc_release() hunk: it needs no change since the subsequent unhash there is already a safe no-op - fixed premature-unhash issue present in v3: smc_conn_free() must not unhash because smc_conn_abort() calls it before smc_switch_to_fallback() in both smc_listen_decline() and smc_connect_rdma() error paths; unhashing there would make live fallback sockets invisible to smcss - likewise, the ISM/RDMA retry loops call smc_conn_abort() on a failed attempt and then smc_conn_create() on the next device; unhashing in smc_conn_free() would permanently hide the established connection from smc_diag since smc_conn_create() does not re-hash the socket Changes in v3: - redesigned as a single patch; dropped the lgr_lnk_lock spinlock approach and the 2-patch split Changes in v2: - split into a 2-patch series; patch 1/2 adds per-connection lgr_lnk_lock infrastructure to smc_core, patch 2/2 fixes the diag dump path using it net/smc/af_smc.c | 10 +++++++--- net/smc/smc_close.c | 3 +++ net/smc/smc_core.c | 1 + net/smc/smc_diag.c | 12 ++++++++---- 4 files changed, 17 insertions(+), 9 deletions(-) diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index e9f93b3ab435..2f8308aa7daf 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -976,7 +976,7 @@ static int smc_connect_fallback(struct smc_sock *smc, int reason_code) smc_copy_sock_settings_to_clc(smc); smc->connect_nonblock = 0; if (smc->sk.sk_state == SMC_INIT) - smc->sk.sk_state = SMC_ACTIVE; + smp_store_release(&smc->sk.sk_state, SMC_ACTIVE); return 0; } @@ -1381,7 +1381,7 @@ static int smc_connect_rdma(struct smc_sock *smc, smc_copy_sock_settings_to_clc(smc); smc->connect_nonblock = 0; if (smc->sk.sk_state == SMC_INIT) - smc->sk.sk_state = SMC_ACTIVE; + smp_store_release(&smc->sk.sk_state, SMC_ACTIVE); return 0; connect_abort: @@ -1484,7 +1484,7 @@ static int smc_connect_ism(struct smc_sock *smc, smc_copy_sock_settings_to_clc(smc); smc->connect_nonblock = 0; if (smc->sk.sk_state == SMC_INIT) - smc->sk.sk_state = SMC_ACTIVE; + smp_store_release(&smc->sk.sk_state, SMC_ACTIVE); return 0; connect_abort: @@ -1951,7 +1951,7 @@ static void smc_listen_out_connected(struct smc_sock *new_smc) struct sock *newsmcsk = &new_smc->sk; if (newsmcsk->sk_state == SMC_INIT) - newsmcsk->sk_state = SMC_ACTIVE; + smp_store_release(&newsmcsk->sk_state, SMC_ACTIVE); smc_listen_out(new_smc); } @@ -1965,7 +1965,7 @@ static void smc_listen_out_err(struct smc_sock *new_smc) this_cpu_inc(net->smc.smc_stats->srv_hshake_err_cnt); if (newsmcsk->sk_state == SMC_INIT) sock_put(&new_smc->sk); /* passive closing */ - newsmcsk->sk_state = SMC_CLOSED; + smp_store_release(&newsmcsk->sk_state, SMC_CLOSED); smc_listen_out(new_smc); } diff --git a/net/smc/smc_close.c b/net/smc/smc_close.c index bb0313ef5f7c..aa6363abdd74 100644 --- a/net/smc/smc_close.c +++ b/net/smc/smc_close.c @@ -154,6 +154,7 @@ void smc_close_active_abort(struct smc_sock *smc) if (sk->sk_state != SMC_PEERABORTWAIT) break; sk->sk_state = SMC_CLOSED; + sk->sk_prot->unhash(sk); smc_conn_free(&smc->conn); release_clcsock = true; sock_put(sk); /* passive closing */ @@ -165,6 +166,7 @@ void smc_close_active_abort(struct smc_sock *smc) if (sk->sk_state != SMC_PEERABORTWAIT) break; sk->sk_state = SMC_CLOSED; + sk->sk_prot->unhash(sk); smc_conn_free(&smc->conn); release_clcsock = true; break; @@ -433,6 +435,7 @@ static void smc_close_passive_work(struct work_struct *work) sk->sk_state_change(sk); if ((sk->sk_state == SMC_CLOSED) && (sock_flag(sk, SOCK_DEAD) || !sk->sk_socket)) { + sk->sk_prot->unhash(sk); smc_conn_free(conn); if (smc->clcsock) release_clcsock = true; diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c index 9974149659c2..663926465ba7 100644 --- a/net/smc/smc_core.c +++ b/net/smc/smc_core.c @@ -1517,6 +1517,7 @@ static void smc_conn_kill(struct smc_connection *conn, bool soft) { struct smc_sock *smc = container_of(conn, struct smc_sock, conn); + smc->sk.sk_prot->unhash(&smc->sk); if (conn->lgr->is_smcd && conn->lgr->peer_shutdown) conn->local_tx_ctrl.conn_state_flags.peer_conn_abort = 1; else diff --git a/net/smc/smc_diag.c b/net/smc/smc_diag.c index bf0beaa23bdb..36a3b8f31f28 100644 --- a/net/smc/smc_diag.c +++ b/net/smc/smc_diag.c @@ -87,10 +87,11 @@ static int __smc_diag_dump(struct sock *sk, struct sk_buff *skb, r = nlmsg_data(nlh); smc_diag_msg_common_fill(r, sk); - r->diag_state = sk->sk_state; + r->diag_state = smp_load_acquire(&sk->sk_state); if (smc->use_fallback) r->diag_mode = SMC_DIAG_MODE_FALLBACK_TCP; - else if (smc_conn_lgr_valid(&smc->conn) && smc->conn.lgr->is_smcd) + else if (r->diag_state != SMC_INIT && + smc_conn_lgr_valid(&smc->conn) && smc->conn.lgr->is_smcd) r->diag_mode = SMC_DIAG_MODE_SMCD; else r->diag_mode = SMC_DIAG_MODE_SMCR; @@ -103,6 +104,9 @@ static int __smc_diag_dump(struct sock *sk, struct sk_buff *skb, if (nla_put(skb, SMC_DIAG_FALLBACK, sizeof(fallback), &fallback) < 0) goto errout; + if (r->diag_state == SMC_INIT || r->diag_state == SMC_CLOSED) + goto out; + if ((req->diag_ext & (1 << (SMC_DIAG_CONNINFO - 1))) && smc->conn.alert_token_local) { struct smc_connection *conn = &smc->conn; @@ -154,8 +158,7 @@ static int __smc_diag_dump(struct sock *sk, struct sk_buff *skb, .lnk[0].link_id = link->link_id, }; - memcpy(linfo.lnk[0].ibname, link->smcibdev->ibdev->name, - sizeof(link->smcibdev->ibdev->name)); + memcpy(linfo.lnk[0].ibname, link->ibname, sizeof(link->ibname)); smc_gid_be16_convert(linfo.lnk[0].gid, link->gid); smc_gid_be16_convert(linfo.lnk[0].peer_gid, link->peer_gid); @@ -185,6 +188,7 @@ static int __smc_diag_dump(struct sock *sk, struct sk_buff *skb, goto errout; } +out: nlmsg_end(skb, nlh); return 0; -- 2.50.1 (Apple Git-155)