diff options
author | Vadim Yanitskiy <vyanitskiy@sysmocom.de> | 2020-06-18 22:29:56 +0700 |
---|---|---|
committer | fixeria <vyanitskiy@sysmocom.de> | 2020-06-23 12:53:50 +0000 |
commit | 6281d4f8692729dc0022ea7a6a2068972d58e9b6 (patch) | |
tree | 847de77d79525638ba9bcdfffd897447f55c4ccb /src/osmo-bsc/osmo_bsc_bssap.c | |
parent | df60b51f1045b41723f7c07890575b8f930cab07 (diff) |
fix crashes due to OSMO_ASSERT(conn->lchan)
Starting from ttcn3-bsc-test-sccplite build #777, it was noticed
that osmo-bsc crashes with the following message:
Assert failed conn->lchan include/osmocom/bsc/gsm_data.h:1376
The cause of this is a recently merged patch that calls conn_get_bts() during
assignment_fsm rate counter dispatch:
"Count assignment rates per BTS as well"
commit b5ccf09fc4042c7fb1fdaaa6263961c40b32564e
Change-Id I0009e51d4caf68e762138d98e2e23d49acc3cc1a
The root cause being that the assignment_fsm attempts to count an Assignment
event for a BTS after the lchan has already been released and disassociated
from the conn.
The assertion is found in conn_get_bts(), which is used in various places. In
fact, each caller is a potential DoS risk -- though most are in code paths that
are guaranteed to have an lchan and bts present, having an OSMO_ASSERT() on the
relatively volatile presence of an lchan is not a good idea for osmo-bsc's
stability and error resilience.
- Change conn_get_bts() to return NULL in the lack of an lchan.
- Adjust all callers of conn_get_bts() to gracefully handle a NULL return val.
- Same for cgi_for_msc() and callers, closely related.
Here is a backtrace:
Program received signal SIGABRT
pwndbg> bt
0x0000555555be6e52 in conn_get_bts (conn=0x622000057160) at include/osmocom/bsc/gsm_data.h:1376
0x0000555555c1edc8 in assignment_fsm_timer_cb (fi=0x612000060220) at assignment_fsm.c:758
0x00007ffff72b1104 in fsm_tmr_cb (data=0x612000060220) at libosmocore/src/fsm.c:325
0x00007ffff72ab062 in osmo_timers_update () at libosmocore/src/timer.c:257
0x00007ffff72ab5d2 in _osmo_select_main (polling=0) at libosmocore/src/select.c:260
0x00007ffff72abd2f in osmo_select_main_ctx (polling=<optimized out>) at libosmocore/src/select.c:291
0x0000555555e1b81b in main (argc=3, argv=0x7fffffffe1b8) at osmo_bsc_main.c:953
0x00007ffff6752002 in __libc_start_main () from /usr/lib/libc.so.6
0x0000555555b61bbe in _start ()
In the case of the assignment_fsm counter, we now miss a chance to increase a
BTS counter for a failed Assignment, but this is a separate problem. The main
point of this patch is that osmo-bsc must not crash.
Related: OS#4620, OS#4619
Patch-by: fixeria
Tweaked-by: neels
Fixes: I0009e51d4caf68e762138d98e2e23d49acc3cc1a
Change-Id: Id681dfb0ad654bdb4b71805d1ad4f39a8bf6bbd1
Diffstat (limited to 'src/osmo-bsc/osmo_bsc_bssap.c')
-rw-r--r-- | src/osmo-bsc/osmo_bsc_bssap.c | 24 |
1 files changed, 14 insertions, 10 deletions
diff --git a/src/osmo-bsc/osmo_bsc_bssap.c b/src/osmo-bsc/osmo_bsc_bssap.c index 6b225e44e..2deb7f46b 100644 --- a/src/osmo-bsc/osmo_bsc_bssap.c +++ b/src/osmo-bsc/osmo_bsc_bssap.c @@ -478,7 +478,6 @@ static int bssmap_handle_cipher_mode(struct gsm_subscriber_connection *conn, struct msgb *msg, unsigned int payload_length) { uint16_t len; - struct gsm_network *network = NULL; const uint8_t *data; struct tlv_parsed tp; struct msgb *resp; @@ -522,7 +521,6 @@ static int bssmap_handle_cipher_mode(struct gsm_subscriber_connection *conn, goto reject; } - network = conn_get_bts(conn)->network; data = TLVP_VAL(&tp, GSM0808_IE_ENCRYPTION_INFORMATION); enc_bits_msc = data[0]; enc_key = &data[1]; @@ -540,10 +538,10 @@ static int bssmap_handle_cipher_mode(struct gsm_subscriber_connection *conn, /* The bit-mask of permitted ciphers from the MSC (sent in ASSIGNMENT COMMAND) is intersected * with the vty-configured mask a the BSC. Finally, the best (highest) possible cipher is * chosen. */ - chosen_cipher = select_best_cipher(enc_bits_msc, network->a5_encryption_mask); + chosen_cipher = select_best_cipher(enc_bits_msc, bsc_gsmnet->a5_encryption_mask); if (chosen_cipher < 0) { LOGP(DMSC, LOGL_ERROR, "Reject: no overlapping A5 ciphers between BSC (0x%02x) " - "and MSC (0x%02x)\n", network->a5_encryption_mask, enc_bits_msc); + "and MSC (0x%02x)\n", bsc_gsmnet->a5_encryption_mask, enc_bits_msc); reject_cause = GSM0808_CAUSE_CIPHERING_ALGORITHM_NOT_SUPPORTED; goto reject; } @@ -663,17 +661,23 @@ static int select_codecs(struct assignment_request *req, struct gsm0808_channel_ { int rc, i, nc = 0; struct bsc_msc_data *msc; + struct gsm_bts *bts = conn_get_bts(conn); + + if (!bts) { + LOGP(DMSC, LOGL_ERROR, "No lchan, cannot select codecs\n"); + return -EINVAL; + } msc = conn->sccp.msc; switch (ct->ch_rate_type) { case GSM0808_SPEECH_FULL_BM: - rc = match_codec_pref(&req->ch_mode_rate[nc], ct, &conn->codec_list, msc, conn_get_bts(conn), + rc = match_codec_pref(&req->ch_mode_rate[nc], ct, &conn->codec_list, msc, bts, RATE_PREF_FR); nc += (rc == 0); break; case GSM0808_SPEECH_HALF_LM: - rc = match_codec_pref(&req->ch_mode_rate[nc], ct, &conn->codec_list, msc, conn_get_bts(conn), + rc = match_codec_pref(&req->ch_mode_rate[nc], ct, &conn->codec_list, msc, bts, RATE_PREF_HR); nc += (rc == 0); break; @@ -681,19 +685,19 @@ static int select_codecs(struct assignment_request *req, struct gsm0808_channel_ case GSM0808_SPEECH_PERM_NO_CHANGE: case GSM0808_SPEECH_FULL_PREF_NO_CHANGE: case GSM0808_SPEECH_FULL_PREF: - rc = match_codec_pref(&req->ch_mode_rate[nc], ct, &conn->codec_list, msc, conn_get_bts(conn), + rc = match_codec_pref(&req->ch_mode_rate[nc], ct, &conn->codec_list, msc, bts, RATE_PREF_FR); nc += (rc == 0); - rc = match_codec_pref(&req->ch_mode_rate[nc], ct, &conn->codec_list, msc, conn_get_bts(conn), + rc = match_codec_pref(&req->ch_mode_rate[nc], ct, &conn->codec_list, msc, bts, RATE_PREF_HR); nc += (rc == 0); break; case GSM0808_SPEECH_HALF_PREF_NO_CHANGE: case GSM0808_SPEECH_HALF_PREF: - rc = match_codec_pref(&req->ch_mode_rate[nc], ct, &conn->codec_list, msc, conn_get_bts(conn), + rc = match_codec_pref(&req->ch_mode_rate[nc], ct, &conn->codec_list, msc, bts, RATE_PREF_HR); nc += (rc == 0); - rc = match_codec_pref(&req->ch_mode_rate[nc], ct, &conn->codec_list, msc, conn_get_bts(conn), + rc = match_codec_pref(&req->ch_mode_rate[nc], ct, &conn->codec_list, msc, bts, RATE_PREF_FR); nc += (rc == 0); break; |