Change in osmo-bsc[master]: Fix heap-use-after-free due to OML link destruction

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Pau Espin Pedrol gerrit-no-reply at lists.osmocom.org
Thu Aug 23 14:45:12 UTC 2018


Pau Espin Pedrol has uploaded this change for review. ( https://gerrit.osmocom.org/10578


Change subject: Fix heap-use-after-free due to OML link destruction
......................................................................

Fix heap-use-after-free due to OML link destruction

Fixes: OS#3495
Change-Id: I7c794c763481c28e8c35dc9b11d27969e16feb3c
---
M include/osmocom/bsc/gsm_data.h
M include/osmocom/bsc/ipaccess.h
M src/osmo-bsc/bts_ipaccess_nanobts.c
M src/osmo-bsc/osmo_bsc_main.c
4 files changed, 31 insertions(+), 2 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-bsc refs/changes/78/10578/1

diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h
index f85887a..b827d0a 100644
--- a/include/osmocom/bsc/gsm_data.h
+++ b/include/osmocom/bsc/gsm_data.h
@@ -923,6 +923,8 @@
 	struct gsm_e1_subslot oml_e1_link;
 	uint8_t oml_tei;
 	struct e1inp_sign_link *oml_link;
+	/* Timer to use for deferred drop of OML link, see \ref ipaccess_drop_oml_deferred */
+	struct osmo_timer_list oml_drop_link_timer;
 	/* when OML link was established */
 	time_t uptime;
 
diff --git a/include/osmocom/bsc/ipaccess.h b/include/osmocom/bsc/ipaccess.h
index 3d0f612..692e795 100644
--- a/include/osmocom/bsc/ipaccess.h
+++ b/include/osmocom/bsc/ipaccess.h
@@ -31,6 +31,7 @@
 } __attribute__((packed));
 
 void ipaccess_drop_oml(struct gsm_bts *bts);
+void ipaccess_drop_oml_deferred(struct gsm_bts *bts);
 void ipaccess_drop_rsl(struct gsm_bts_trx *trx);
 
 struct sdp_header_item {
diff --git a/src/osmo-bsc/bts_ipaccess_nanobts.c b/src/osmo-bsc/bts_ipaccess_nanobts.c
index 80f7c9c..fec4147 100644
--- a/src/osmo-bsc/bts_ipaccess_nanobts.c
+++ b/src/osmo-bsc/bts_ipaccess_nanobts.c
@@ -166,7 +166,7 @@
 			enum abis_nm_chan_comb ccomb =
 						abis_nm_chcomb4pchan(ts->pchan_from_config);
 			if (abis_nm_set_channel_attr(ts, ccomb) == -EINVAL) {
-				ipaccess_drop_oml(trx->bts);
+				ipaccess_drop_oml_deferred(trx->bts);
 				return -1;
 			}
 			abis_nm_chg_adm_state(trx->bts, obj_class,
@@ -400,6 +400,9 @@
 	struct gsm_bts *rdep_bts;
 	struct gsm_bts_trx *trx;
 
+	/* First of all, remove deferred drop if enabled */
+	osmo_timer_del(&bts->oml_drop_link_timer);
+
 	if (!bts->oml_link)
 		return;
 
@@ -432,6 +435,29 @@
 	}
 }
 
+/*! Callback for  \ref ipaccess_drop_oml_deferred_cb.
+ */
+static void ipaccess_drop_oml_deferred_cb(void *data)
+{
+	struct gsm_bts *bts = (struct gsm_bts *) data;
+	ipaccess_drop_oml(bts);
+}
+/*! Deferr \ref ipacces_drop_oml through a timer to avoid dropping structures in
+ *  current code context. This may be needed if we want to destroy the OML link
+ *  while being called from a lower layer "struct osmo_fd" cb, were it is
+ *  mandatory to return -EBADF if the osmo_fd has been destroyed. In case code
+ *  destroying an OML link is called through an osmo_signal, it becomes
+ *  impossible to return any value, thus deferring the destruction is required.
+ */
+void ipaccess_drop_oml_deferred(struct gsm_bts *bts)
+{
+	if (!osmo_timer_pending(&bts->oml_drop_link_timer) && bts->oml_link) {
+		LOGP(DLINP, LOGL_NOTICE, "(bts=%d) Deferring Drop of OML link.\n", bts->nr);
+		osmo_timer_setup(&bts->oml_drop_link_timer, ipaccess_drop_oml_deferred_cb, bts);
+		osmo_timer_schedule(&bts->oml_drop_link_timer, 0, 0);
+	}
+}
+
 /* This function is called once the OML/RSL link becomes up. */
 static struct e1inp_sign_link *
 ipaccess_sign_link_up(void *unit_data, struct e1inp_line *line,
diff --git a/src/osmo-bsc/osmo_bsc_main.c b/src/osmo-bsc/osmo_bsc_main.c
index 8ff0e8a..0dbe81c 100644
--- a/src/osmo-bsc/osmo_bsc_main.c
+++ b/src/osmo-bsc/osmo_bsc_main.c
@@ -191,7 +191,7 @@
 	}
 
 	if (is_ipaccess_bts(nack->bts))
-		ipaccess_drop_oml(nack->bts);
+		ipaccess_drop_oml_deferred(nack->bts);
 
 	return 0;
 }

-- 
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Gerrit-Project: osmo-bsc
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: I7c794c763481c28e8c35dc9b11d27969e16feb3c
Gerrit-Change-Number: 10578
Gerrit-PatchSet: 1
Gerrit-Owner: Pau Espin Pedrol <pespin at sysmocom.de>
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