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net/smc: free stashed qentry before overwrite in REQ_ADD_LINK to ADD_LINK transition

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When smc_llc_event_handler() transitions the local LLC flow from
SMC_LLC_FLOW_REQ_ADD_LINK to SMC_LLC_FLOW_ADD_LINK on arrival of an ADD_LINK
request, it calls smc_llc_flow_qentry_set() unconditionally:

	if (lgr->llc_flow_lcl.type == SMC_LLC_FLOW_REQ_ADD_LINK) {
		lgr->llc_flow_lcl.type = SMC_LLC_FLOW_ADD_LINK;
		smc_llc_flow_qentry_set(&lgr->llc_flow_lcl, qentry);
		...
	}

A CONFIRM_LINK or ADD_LINK_CONT arriving while flow->type is
SMC_LLC_FLOW_REQ_ADD_LINK is stashed into flow->qentry via the
SMC_LLC_CONFIRM_LINK / SMC_LLC_ADD_LINK_CONT handler (which stores into
flow->qentry for any non-NONE flow type).  When the subsequent ADD_LINK
arrives, the REQ_ADD_LINK branch overwrites flow->qentry with the new pointer
without first freeing the stashed allocation, leaking one kmalloc object.

The stashed entry has no consumer: smc_llc_wait() is only called from
llc_add_link_work, which is not yet scheduled while the flow type remains
REQ_ADD_LINK.  No waiter is sleeping on llc_msg_waiter at this point.
It is safe to unconditionally free any stashed qentry before
the overwrite.

Call smc_llc_flow_qentry_del() before smc_llc_flow_qentry_set() in the
REQ_ADD_LINK branch.  smc_llc_flow_qentry_del() already checks flow->qentry
before freeing, so the normal path where no entry is stashed is a no-op.

Fixes: b4ba4652b3 ("net/smc: extend LLC layer for SMC-Rv2")
Reviewed-by: Hidayath Khan <hidayath@linux.ibm.com>
Signed-off-by: Mahanta Jambigi <mjambigi@linux.ibm.com>
Link: https://patch.msgid.link/20260818073107.466506-1-mjambigi@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Mahanta Jambigi
2026-08-18 09:31:07 +02:00
committed by Jakub Kicinski
parent f2849b1fd0
commit 036322025d
1 changed files with 2 additions and 0 deletions
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2
net/smc/smc_llc.c
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@@ -1911,6 +1911,8 @@ static void smc_llc_event_handler(struct smc_llc_qentry *qentry)
if (lgr->llc_flow_lcl.type ==
SMC_LLC_FLOW_REQ_ADD_LINK) {
/* server started add_link processing */
/* free any qentry stashed in REQ_ADD_LINK state */
smc_llc_flow_qentry_del(&lgr->llc_flow_lcl);
lgr->llc_flow_lcl.type = SMC_LLC_FLOW_ADD_LINK;
smc_llc_flow_qentry_set(&lgr->llc_flow_lcl,
qentry);