ns2: Avoid use-after-free when SGSN-side non-persistent SNS-NSE fails
alive_timeout_handler() changes the state to RECOVERING which calls
ns2_st_alive_onenter()->ns2_nse_notify_unblocked(unblocked=false)->
ns2_sns_notify_alive(unblocked=false)
When all (signalling) NSVCs have failed and gss->role is SGSN and not
persistent sns_failed() calls gprs_ns2_free_nse() which talloc_free()s
the nse before returning.
The next line in ns2_nse_notify_unblocked() tries to read nse->alive which then causes the
use-after-free.
Change-Id: I0486a77fd3e21fd3904bd19e4e0225ffbf654935
Related: OS#5302
diff --git a/src/gb/gprs_ns2.c b/src/gb/gprs_ns2.c
index 3bb04ae..02d2266 100644
--- a/src/gb/gprs_ns2.c
+++ b/src/gb/gprs_ns2.c
@@ -1392,11 +1392,16 @@
void ns2_nse_notify_unblocked(struct gprs_ns2_vc *nsvc, bool unblocked)
{
struct gprs_ns2_nse *nse = nsvc->nse;
+ struct gprs_ns2_inst *nsi = nse->nsi;
+ uint16_t nsei = nse->nsei;
ns2_nse_data_sum(nse);
ns2_sns_notify_alive(nse, nsvc, unblocked);
- if (unblocked == nse->alive)
+ /* NSE could have been freed, try to get it again */
+ nse = gprs_ns2_nse_by_nsei(nsi, nsei);
+
+ if (!nse || unblocked == nse->alive)
return;
/* wait until both data_weight and sig_weight are != 0 before declaring NSE as alive */