fixeria has uploaded this change for review. ( https://gerrit.osmocom.org/c/libosmo-abis/+/32661 )

Change subject: fix use-after-free in ipaccess_bts_keepalive_fsm_alloc() ......................................................................

fix use-after-free in ipaccess_bts_keepalive_fsm_alloc()

In ipaccess_bts_keepalive_fsm_alloc() we allocate a keepalive FSM instance as a child of the respective struct ipa_client_conn, and store the pointer to the respective struct e1inp_ts.

+ struct e1inp_line | ---+ struct ipaccess_line (void *driver_data) | | | ---+ struct ipa_client_conn *ipa_cli[NUM_E1_TS] // <-- parent | ---+ struct e1inp_ts ts[NUM_E1_TS] | | | ---+ .driver.ipaccess.ka_fsm // <-- pointer

When an ipaccess connection (be it OML or RSL) goes down and then up again, for instance if the BSC gets restarted, osmo-bts crashes. The problem is that struct ipa_client_conn gets free()ed before the associated FSM instance gets terminated:

* e1inp_ipa_bts_rsl_connect_n() is called ** calling e1inp_ipa_bts_rsl_close_n() *** this function free()s struct ipa_client_conn *** (!) as well as the struct osmo_fsm_inst (talloc child) ** calling ipaccess_bts_keepalive_fsm_alloc() *** calling ipaccess_keepalive_fsm_cleanup() **** accessing free()d e1i_ts->driver.ipaccess.ka_fsm **** BOOOM! segmentation fault

Fix this by calling ipaccess_keepalive_fsm_cleanup() before free()ing the associated struct ipa_client_conn.

Note that ipaccess_bsc_keepalive_fsm_alloc() is not affected because it's allocating keepalive FSMs using the global tall_ipa_ctx.

Change-Id: Ic56c4b5b7b24b63104908a0c24f2f645ba4c5c1b Related: SYS#6438 (cherry picked from commit f6bde0f521155f1d2a073181cfca97df83de2684) --- M src/input/ipaccess.c 1 file changed, 50 insertions(+), 1 deletion(-)

git pull ssh://gerrit.osmocom.org:29418/libosmo-abis refs/changes/61/32661/1

diff --git a/src/input/ipaccess.c b/src/input/ipaccess.c index 8a52591..418606e 100644 --- a/src/input/ipaccess.c +++ b/src/input/ipaccess.c @@ -192,7 +192,7 @@ struct e1inp_line *line = e1i_ts->line; struct osmo_fsm_inst *ka_fsm;

- ipaccess_keepalive_fsm_cleanup(e1i_ts); + OSMO_ASSERT(e1i_ts->driver.ipaccess.ka_fsm == NULL); if (!line->ipa_kap) return;

@@ -1207,6 +1207,7 @@ int e1inp_ipa_bts_rsl_close_n(struct e1inp_line *line, uint8_t trx_nr) { struct ipaccess_line *il; + struct e1inp_ts *e1i_ts;

if (E1INP_SIGN_RSL+trx_nr-1 >= NUM_E1_TS) { LOGP(DLINP, LOGL_ERROR, @@ -1218,6 +1219,9 @@ if (!il) return 0; /* Nothing to do, no lines created */

+ e1i_ts = e1inp_line_ipa_rsl_ts(line, trx_nr); + ipaccess_keepalive_fsm_cleanup(e1i_ts); + if (il->ipa_cli[1 + trx_nr]) { ipa_client_conn_close(il->ipa_cli[1 + trx_nr]); ipa_client_conn_destroy(il->ipa_cli[1 + trx_nr]);