AZL-102797

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:

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.