BUG/MEDIUM: quic: Possible crash during retransmissions and heavy load

This bug could be reproduced with -dMfail and dectected by libasan as follows:

$ ASAN_OPTIONS=disable_coredump=0:unmap_shadow_on_exit=1:abort_on_error=f quic-freeze.cfg -dMfail -dMno-cache -dM0x55
=================================================================
==82989==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7ffc 0x560790cc4749 bp 0x7fff8e0e8e30 sp 0x7fff8e0e8e28
WRITE of size 8 at 0x7fff8e0ea338 thread T0
    #0 0x560790cc4748 in qc_frm_free src/quic_frame.c:1222
    #1 0x560790cc5260 in qc_release_frm src/quic_frame.c:1261
    #2 0x560790d1de99 in qc_treat_acked_tx_frm src/quic_rx.c:312
    #3 0x560790d1e708 in qc_ackrng_pkts src/quic_rx.c:370
    #4 0x560790d22a1d in qc_parse_ack_frm src/quic_rx.c:694
    #5 0x560790d25daa in qc_parse_pkt_frms src/quic_rx.c:988
    #6 0x560790d2a509 in qc_treat_rx_pkts src/quic_rx.c:1373
    #7 0x560790c72d45 in quic_conn_io_cb src/quic_conn.c:906
    #8 0x560791207847 in run_tasks_from_lists src/task.c:596
    #9 0x5607912095f0 in process_runnable_tasks src/task.c:876
    #10 0x560791135564 in run_poll_loop src/haproxy.c:2966
    #11 0x5607911363af in run_thread_poll_loop src/haproxy.c:3165
    #12 0x56079113938c in main src/haproxy.c:3862
    #13 0x7f92606edd09 in __libc_start_main ../csu/libc-start.c:308
    #14 0x560790bcd529 in _start (/home/flecaille/src/haproxy/haproxy+0x

Address 0x7fff8e0ea338 is located in stack of thread T0 at offset 1032 i
    #0 0x560790d29b52 in qc_treat_rx_pkts src/quic_rx.c:1341

  This frame has 2 object(s):
    [32, 48) 'ar' (line 1380)
    [64, 1088) '_msg' (line 1368) <== Memory access at offset 1032 is inable
HINT: this may be a false positive if your program uses some custom stacnism, swapcontext or vfork
      (longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-use-after-scope src/quic_frame.c:1222 i
Shadow bytes around the buggy address:
  0x100071c15410: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
  0x100071c15420: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
  0x100071c15430: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
  0x100071c15440: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
  0x100071c15450: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
=>0x100071c15460: f8 f8 f8 f8 f8 f8 f8[f8]f8 f8 f8 f8 f8 f8 f3 f3
  0x100071c15470: f3 f3 f3 f3 f3 f3 f3 f3 f3 f3 f3 f3 f3 f3 00 00
  0x100071c15480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x100071c15490: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x100071c154a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x100071c154b0: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 04 f3 f3 f3
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
  Shadow gap:              cc
==82989==ABORTING
AddressSanitizer:DEADLYSIGNAL
AddressSanitizer:DEADLYSIGNAL
AddressSanitizer:DEADLYSIGNAL
AddressSanitizer:DEADLYSIGNAL
AddressSanitizer:DEADLYSIGNAL
AddressSanitizer:DEADLYSIGNAL
Aborted (core dumped)

Note that a coredump could not always be produced with all compilers. This was
always the case with clang 11.

When allocating frames to be retransmitted from qc_dgrams_retransmit(), if they
could not be sent for any reason, they could remain attached to a local list to
qc_dgrams_retransmit() and trigger a crash with libasan when releasing the
original frames they were duplicated from.

To fix this, always release the frames which could not be sent during
retransmissions calling qc_free_frm_list() where needed.

Must be backported as far as 2.6.

diff --git a/src/quic_tx.c b/src/quic_tx.c
index 229316ad70c5f64a4c84d781c60c1ebc3f1a4037..4f4551b162c527201c4c987795ef4cee4b949ac2 100644 (file)
--- a/src/quic_tx.c
+++ b/src/quic_tx.c
@@ -147,7 +147,7 @@ static void qc_dup_pkt_frms(struct quic_conn *qc,
                TRACE_DEVEL("built probing frame", QUIC_EV_CONN_PRSAFRM, qc, origin);
                if (origin->pkt) {
                        TRACE_DEVEL("duplicated from packet", QUIC_EV_CONN_PRSAFRM,
-                                   qc, NULL, &origin->pkt->pn_node.key);
+                                   qc, dup_frm, &origin->pkt->pn_node.key);
                }
                else {
                        /* <origin> is a frame which was sent from a packet detected as lost. */
@@ -1308,6 +1308,7 @@ int qc_send_hdshk_pkts(struct quic_conn *qc, int old_data,
 int qc_dgrams_retransmit(struct quic_conn *qc)
 {
        int ret = 0;
+       int sret;
        struct quic_pktns *ipktns = qc->ipktns;
        struct quic_pktns *hpktns = qc->hpktns;
        struct quic_pktns *apktns = qc->apktns;
@@ -1335,21 +1336,24 @@ int qc_dgrams_retransmit(struct quic_conn *qc)
                                qc->iel->retrans_frms = &ifrms;
                                if (qc->hel)
                                        qc->hel->retrans_frms = &hfrms;
-                               if (!qc_send_hdshk_pkts(qc, 1, qc->iel, qc->hel))
+                               sret = qc_send_hdshk_pkts(qc, 1, qc->iel, qc->hel);
+                               qc_free_frm_list(qc, &ifrms);
+                               qc_free_frm_list(qc, &hfrms);
+                               if (!sret)
                                        goto leave;
-                               /* Put back unsent frames in their packet number spaces */
-                               LIST_SPLICE(&ipktns->tx.frms, &ifrms);
-                               if (hpktns)
-                                       LIST_SPLICE(&hpktns->tx.frms, &hfrms);
                        }
                        else {
                                /* We are in the case where the anti-amplification limit will be
-                                * reached after having sent this datagram. There is no need to
-                                * send more than one datagram.
+                                * reached after having sent this datagram or some handshake frames
+                                * could not be allocated. There is no need to send more than one
+                                * datagram.
                                 */
                                ipktns->tx.pto_probe = 1;
                                qc->iel->retrans_frms = &ifrms;
-                               if (!qc_send_hdshk_pkts(qc, 0, qc->iel, NULL))
+                               sret = qc_send_hdshk_pkts(qc, 0, qc->iel, NULL);
+                               qc_free_frm_list(qc, &ifrms);
+                               qc_free_frm_list(qc, &hfrms);
+                               if (!sret)
                                        goto leave;
 
                                break;
@@ -1374,11 +1378,10 @@ int qc_dgrams_retransmit(struct quic_conn *qc)
                                if (!LIST_ISEMPTY(&frms1)) {
                                        hpktns->tx.pto_probe = 1;
                                        qc->hel->retrans_frms = &frms1;
-                                       if (!qc_send_hdshk_pkts(qc, 1, qc->hel, NULL))
+                                       sret = qc_send_hdshk_pkts(qc, 1, qc->hel, NULL);
+                                       qc_free_frm_list(qc, &frms1);
+                                       if (!sret)
                                                goto leave;
-
-                                       /* Put back unsent frames into their packet number spaces */
-                                       LIST_SPLICE(&hpktns->tx.frms, &frms1);
                                }
                        }
                        TRACE_STATE("no more need to probe Handshake packet number space",
@@ -1393,25 +1396,23 @@ int qc_dgrams_retransmit(struct quic_conn *qc)
                        qc_prep_fast_retrans(qc, apktns, &frms1, &frms2);
                        TRACE_PROTO("Avail. ack eliciting frames", QUIC_EV_CONN_FRMLIST, qc, &frms1);
                        TRACE_PROTO("Avail. ack eliciting frames", QUIC_EV_CONN_FRMLIST, qc, &frms2);
+
                        if (!LIST_ISEMPTY(&frms1)) {
                                apktns->tx.pto_probe = 1;
-                               if (!qc_send_app_probing(qc, &frms1)) {
-                                       qc_free_frm_list(qc, &frms1);
+                               sret = qc_send_app_probing(qc, &frms1);
+                               qc_free_frm_list(qc, &frms1);
+                               if (!sret) {
                                        qc_free_frm_list(qc, &frms2);
                                        goto leave;
                                }
-
-                               /* Put back unsent frames into their packet number spaces */
-                               LIST_SPLICE(&apktns->tx.frms, &frms1);
                        }
+
                        if (!LIST_ISEMPTY(&frms2)) {
                                apktns->tx.pto_probe = 1;
-                               if (!qc_send_app_probing(qc, &frms2)) {
-                                       qc_free_frm_list(qc, &frms2);
+                               sret = qc_send_app_probing(qc, &frms2);
+                               qc_free_frm_list(qc, &frms2);
+                               if (!sret)
                                        goto leave;
-                               }
-                               /* Put back unsent frames into their packet number spaces */
-                               LIST_SPLICE(&apktns->tx.frms, &frms2);
                        }
                        TRACE_STATE("no more need to probe 01RTT packet number space",
                                    QUIC_EV_CONN_TXPKT, qc);