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net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket

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smc_cdc_rx_handler() looks up the connection by token under the link
group's conns_lock, drops the lock, and then dereferences conn and the
smc_sock derived from it, ending in sock_hold(&smc->sk) inside
smc_cdc_msg_recv(). No reference is held across the lock release.

The only reference pinning the socket while the connection is
discoverable in the link group is taken in smc_lgr_register_conn()
(sock_hold) and dropped in __smc_lgr_unregister_conn() (sock_put), both
under conns_lock. Once the handler drops conns_lock, a concurrent
close() -> smc_release() -> smc_conn_free() -> smc_lgr_unregister_conn()
can drop that reference and free the smc_sock, so the handler's later
sock_hold() runs on freed memory:

  WARNING: lib/refcount.c:25 at refcount_warn_saturate
  Workqueue: rxe_wq do_work
   refcount_warn_saturate (lib/refcount.c:25)
   smc_cdc_msg_recv (net/smc/smc_cdc.c:430)
   smc_cdc_rx_handler (net/smc/smc_cdc.c:502)
   smc_wr_rx_tasklet_fn (net/smc/smc_wr.c:445)
   tasklet_action_common (kernel/softirq.c:938)
   handle_softirqs (kernel/softirq.c:622)
  Kernel panic - not syncing: panic_on_warn set

Only SMC-R is affected. The SMC-D receive tasklet is stopped by
tasklet_kill(&conn->rx_tsklet) in smc_conn_free() before the connection
is unregistered, so it cannot run concurrently with the free.

Take the socket reference while still holding conns_lock, so the
registration reference can no longer be the last one, and drop it once
the handler is done.

Fixes: d7b0e37c1a ("net/smc: restructure CDC message reception")
Reported-by: Weiming Shi <bestswngs@gmail.com>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Xiang Mei <xmei5@asu.edu>
Link: https://patch.msgid.link/20260630183227.2044998-1-xmei5@asu.edu
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Xiang Mei
2026-06-30 11:32:27 -07:00
committed by Paolo Abeni
parent 8b519cbcab
commit 9d160b35cc
1 changed files with 10 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
net/smc/smc_cdc.c
View File

@@ -470,9 +470,9 @@ static void smc_cdc_rx_handler(struct ib_wc *wc, void *buf)
{
struct smc_link *link = (struct smc_link *)wc->qp->qp_context;
struct smc_cdc_msg *cdc = buf;
struct smc_sock *smc = NULL;
struct smc_connection *conn;
struct smc_link_group *lgr;
struct smc_sock *smc;
if (wc->byte_len < offsetof(struct smc_cdc_msg, reserved))
return; /* short message */
@@ -483,21 +483,26 @@ static void smc_cdc_rx_handler(struct ib_wc *wc, void *buf)
lgr = smc_get_lgr(link);
read_lock_bh(&lgr->conns_lock);
conn = smc_lgr_find_conn(ntohl(cdc->token), lgr);
read_unlock_bh(&lgr->conns_lock);
if (!conn || conn->out_of_sync)
if (!conn || conn->out_of_sync) {
read_unlock_bh(&lgr->conns_lock);
return;
}
smc = container_of(conn, struct smc_sock, conn);
sock_hold(&smc->sk);
read_unlock_bh(&lgr->conns_lock);
if (cdc->prod_flags.failover_validation) {
smc_cdc_msg_validate(smc, cdc, link);
return;
goto out;
}
if (smc_cdc_before(ntohs(cdc->seqno),
conn->local_rx_ctrl.seqno))
/* received seqno is old */
return;
goto out;
smc_cdc_msg_recv(smc, cdc);
out:
sock_put(&smc->sk);
}
static struct smc_wr_rx_handler smc_cdc_rx_handlers[] = {