In the Linux kernel, the following vulnerability has been resolved: net/smc: free pending qentry in smc_llc_flow_stop() before memset smc_

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

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

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

 1spin_lock_bh(&lgr->llc_flow_lock);
 2memset(flow, 0, sizeof(*flow));
 3flow->type = SMC_LLC_FLOW_NONE;
 4spin_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.