From b9759dba9ecd2720aab1c91d6824a18e2c0ffbcd Mon Sep 17 00:00:00 2001
From: Ivan Kluchnikov <kluchnikovi@gmail.com>
Date: Thu, 11 May 2017 15:19:23 +0300
Subject: lapd_core: Fix crash in lapd_est_req() function

lapd_est_req() function could be called on uninitialized lapd link
(before lapd_dl_init() and after lapd_dl_exit() functions) due to
invalid usage on higher levels.
In order to prevent using uninitialized lapd link, we should set
LAPD_STATE_NULL state for lapd_datalink in lapd_dl_exit() function.
So all messages for lapd_datalink in null state will be unhandled by
lapd_recv_dlsap() function and lapd_est_req() function will not be
called before lapd_dl_init() function where lapd link state is changed
to idle.

 #0  0x00007f46ecd99aa5 in lapd_est_req (dp=<optimized out>, lctx=0x7f46ed80b8b8) at
     lapd_core.c:1769
 #1  0x00007f46ecd9dda8 in rslms_rx_rll_est_req (msg=msg@entry=0x7f46eeab4940,
     dl=dl@entry=0x7f46ed80b888) at lapdm.c:845
 #2  0x00007f46ecd9fc03 in rslms_rx_rll (lc=0x7f46ed80b398, msg=0x7f46eeab4940) at
     lapdm.c:1157
 #3  lapdm_rslms_recvmsg (msg=0x7f46eeab4940, lc=0x7f46ed80b398) at lapdm.c:1223
 #4  0x00007f46ed63773d in rsl_rx_rll (msg=<optimized out>, trx=<optimized out>) at
     rsl.c:2178
 #5  down_rsl (trx=<optimized out>, msg=<optimized out>) at rsl.c:2541
 #6  0x00007f46ed641529 in sign_link_cb (msg=<optimized out>) at abis.c:169
 #7  0x00007f46ec54b111 in ipaccess_bts_read_cb (link=0x7f46eeab4940, msg=0x0) at
     input/ipaccess.c:807
 #8  0x00007f46ec548a8e in ipa_client_read (link=0x7f46ee26ae30) at input/ipa.c:74
 #9  ipa_client_fd_cb (ofd=<optimized out>, what=1) at input/ipa.c:137
 #10 0x00007f46ecfc726f in osmo_fd_disp_fds (_eset=0x7ffe7a9fcd20, _wset=0x7ffe7a9fcca0,
     _rset=0x7ffe7a9fcc20) at select.c:167
 #11 osmo_select_main (polling=polling@entry=0) at select.c:207
 #12 0x00007f46ed63fc25 in bts_main (argc=5, argv=<optimized out>) at main.c:359
 #13 0x00007f46ebd76f45 in __libc_start_main (main=0x7f46ed61b120 <main>, argc=5,
     argv=0x7ffe7a9fcf18, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>,
 #14 0x00007f46ed61b14e in _start ()

Related: OS#1982
Change-Id: I306dad9b78e3becaef14c5305ec25c312feefe3c
---
 src/gsm/lapd_core.c | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'src')

diff --git a/src/gsm/lapd_core.c b/src/gsm/lapd_core.c
index 166bf9a7..6b580069 100644
--- a/src/gsm/lapd_core.c
+++ b/src/gsm/lapd_core.c
@@ -326,6 +326,10 @@ void lapd_dl_exit(struct lapd_datalink *dl)
 {
 	/* free all ressources except history buffer */
 	lapd_dl_reset(dl);
+
+	/* enter null state */
+	lapd_dl_newstate(dl, LAPD_STATE_NULL);
+
 	/* free history buffer list */
 	talloc_free(dl->tx_hist);
 	dl->tx_hist = NULL;
-- 
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