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authorPau Espin Pedrol <pespin@sysmocom.de>2017-10-16 10:46:36 +0200
committerPau Espin Pedrol <pespin@sysmocom.de>2017-10-17 10:07:00 +0200
commit957ceb1b792a274582e88ed2963dc959f5385ce0 (patch)
treece522eb4f3c781f8e9b6790341f803371d7aaf5d
parent65c6ddebff3e03fe3bdeebf225f013b0bc30773b (diff)
bsc_api: Fix NULL secondary_lchan access in handle_ass_fail
Related: OW#3893 Program terminated with signal SIGSEGV, Segmentation fault. 0 gsm_lchan_name (lchan=lchan@entry=0x0) at gsm_data_shared.c:342 (gdb) bt 0 gsm_lchan_name (lchan=lchan@entry=0x0) at gsm_data_shared.c:342 1 0x0805ab80 in lchan_release (lchan=0x0, sacch_deact=sacch_deact@entry=0, mode=mode@entry=RSL_REL_LOCAL_END) at chan_alloc.c:410 2 0x0805c1dd in handle_ass_fail (msg=0x94142b8, conn=0x9251048) at bsc_api.c:459 3 dispatch_dtap (msg=0x94142b8, link_id=0 '\000', conn=0x9251048) at bsc_api.c:598 4 gsm0408_rcvmsg (msg=msg@entry=0x94142b8, link_id=0 '\000') at bsc_api.c:658 5 0x08058ca2 in abis_rsl_rx_rll (msg=0x94142b8) at abis_rsl.c:1686 6 abis_rsl_rcvmsg (msg=0x94142b8) at abis_rsl.c:2097 7 0xb7e8cf9a in handle_ts1_read (bfd=0x94e8e08) at input/ipaccess.c:271 8 ipaccess_fd_cb (bfd=0x94e8e08, what=1) at input/ipaccess.c:386 9 0xb7ee8434 in osmo_select_main (polling=polling@entry=0) at select.c:158 10 0x0804bd7c in main (argc=6, argv=0xbfc27144) at osmo_bsc_main.c:272 (gdb) print lchan $2 = (const struct gsm_lchan *) 0x0 Possible scenario in which this crash can appear: 1- gsm0808_assign_req() calls handle_new_assignment() which sends an CHAN ACTIVATE msg and arms T10 timer. 2- ACTIVATE ACK is received (handle_chan_ack), which calls gsm48_send_rr_ass_cmd() which sends an ASSIGNMENT CMD, and doesn't disable/modify T10 timer. 3- T10 timeout is triggered (assignment_t10_timeout()), which sets conn->secondary_lchan = NULL 4- Immediately after, the ASSIGNMENT FAILURE message (which might have been already queued) is processed in handle_ass_fail, and then the crash occurs. This race condition is not an issue for handle_ass_compl() path because there's this check there which would trigger most probably if secondary_lchan is NULL: "if (conn->secondary_lchan != msg->lchan)" Change-Id: Ied5bd90b9c06f27135a2e3c46e40d49d27d9a387
-rw-r--r--openbsc/src/libbsc/bsc_api.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/openbsc/src/libbsc/bsc_api.c b/openbsc/src/libbsc/bsc_api.c
index fa4542112..0c16db303 100644
--- a/openbsc/src/libbsc/bsc_api.c
+++ b/openbsc/src/libbsc/bsc_api.c
@@ -485,8 +485,10 @@ static void handle_ass_fail(struct gsm_subscriber_connection *conn,
/* stop the timer and release it */
osmo_timer_del(&conn->T10);
- lchan_release(conn->secondary_lchan, 0, RSL_REL_LOCAL_END);
- conn->secondary_lchan = NULL;
+ if (conn->secondary_lchan) {
+ lchan_release(conn->secondary_lchan, 0, RSL_REL_LOCAL_END);
+ conn->secondary_lchan = NULL;
+ }
gh = msgb_l3(msg);
if (msgb_l3len(msg) - sizeof(*gh) != 1) {