Author: vmaffione
Date: Tue Jun 30 19:34:36 2020
New Revision: 362810
URL: https://svnweb.freebsd.org/changeset/base/362810

Log:
  MFC r362553
  
  iflib: netmap: fix rsync index overrun
  
  In the current iflib_netmap_rxsync, there is nothing that prevents
  kring->nr_hwtail to overrun kring->nr_hwcur during the descriptor
  import phase. This may cause errors in netmap applications, such as:
  
  em1 RX0: fail 'head < kring->nr_hwcur || head > kring->nr_hwtail'
      h 795 c 795 t 282 rh 795 rc 795 rt 282 hc 282 ht 282
  
  Reviewed by:    gallatin
  Differential Revision:  https://reviews.freebsd.org/D25252

Modified:
  stable/12/sys/net/iflib.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/net/iflib.c
==============================================================================
--- stable/12/sys/net/iflib.c   Tue Jun 30 18:08:59 2020        (r362809)
+++ stable/12/sys/net/iflib.c   Tue Jun 30 19:34:36 2020        (r362810)
@@ -1104,6 +1104,7 @@ iflib_netmap_rxsync(struct netmap_kring *kring, int fl
         * rxr->next_check is set to 0 on a ring reinit
         */
        if (netmap_no_pendintr || force_update) {
+               uint32_t hwtail_lim = nm_prev(kring->nr_hwcur, lim);
                int crclen = iflib_crcstrip ? 0 : 4;
                int error, avail;
 
@@ -1113,7 +1114,7 @@ iflib_netmap_rxsync(struct netmap_kring *kring, int fl
                        nm_i = netmap_idx_n2k(kring, nic_i);
                        avail = ctx->isc_rxd_available(ctx->ifc_softc,
                            rxq->ifr_id, nic_i, USHRT_MAX);
-                       for (n = 0; avail > 0; n++, avail--) {
+                       for (n = 0; avail > 0 && nm_i != hwtail_lim; n++, 
avail--) {
                                rxd_info_zero(&ri);
                                ri.iri_frags = rxq->ifr_frags;
                                ri.iri_qsidx = kring->ring_id;
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