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net/smc: free pending qentry in smc_llc_flow_stop() before memset

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smc_llc_flow_stop() resets a flow struct with a blind memset:

	spin_lock_bh(&lgr->llc_flow_lock);
	memset(flow, 0, sizeof(*flow));
	flow->type = SMC_LLC_FLOW_NONE;
	spin_unlock_bh(&lgr->llc_flow_lock);

If flow->qentry is non-NULL at this point the pointer is overwritten without the
allocation being freed, leaking one kmalloc object.

A late-arriving duplicate CONFIRM_LINK or ADD_LINK_CONT message can set
flow->qentry after the legitimate message has been consumed by the waiter via
smc_llc_flow_qentry_clr() (which NULLs the pointer but leaves flow->type
non-zero) but before the flow completes and smc_llc_flow_stop() runs.  In that
window the duplicate is stashed into flow->qentry, and then lost when
smc_llc_flow_stop() zeros the struct.

Call smc_llc_flow_qentry_del() inside the lock before the memset.
smc_llc_flow_qentry_del() already checks flow->qentry before freeing, so the
normal case where no entry is pending is a no-op.

Fixes: 555da9af82 ("net/smc: add event-based llc_flow framework")
Reviewed-by: Hidayath Khan <hidayath@linux.ibm.com>
Signed-off-by: Mahanta Jambigi <mjambigi@linux.ibm.com>
Link: https://patch.msgid.link/20260818073943.1108383-1-mjambigi@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Mahanta Jambigi
2026-08-18 09:39:43 +02:00
committed by Jakub Kicinski
parent 036322025d
commit 5ee0ceddc7
1 changed files with 1 additions and 0 deletions
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1
net/smc/smc_llc.c
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@@ -320,6 +320,7 @@ int smc_llc_flow_initiate(struct smc_link_group *lgr,
void smc_llc_flow_stop(struct smc_link_group *lgr, struct smc_llc_flow *flow)
{
spin_lock_bh(&lgr->llc_flow_lock);
smc_llc_flow_qentry_del(flow);
memset(flow, 0, sizeof(*flow));
flow->type = SMC_LLC_FLOW_NONE;
spin_unlock_bh(&lgr->llc_flow_lock);