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sgsn: Delete PDP contexts properly 

Currently the PDP contexts are hard freed (via sgsn_pdp_ctx_free)
at some places in gprs_gmm.c on the reception of a Detach Req and on
re-use of an IMSI that is already associated with an MM context. This
can lead to segfaults when there is a pending request or a data
indication at libgtp.

This patch add a new function sgsn_pdp_ctx_terminate that de-associates
the PTP context from the MM context, deactivates SNDCP, sets pdp->mm
to NULL and then calls sgsn_delete_pdp_ctx. sgsn_libgtp is updated to
check for pdp->mm being non-NULL before dereferencing it. The
sgsn_pdp_ctx_terminate function will be called for each PDP context of
an MM context before this context is going to be deleted via
sgsn_mm_ctx_free. To ensure, that the ctx->llme (which is accessed
during the deactivation of SNDCP) remains valid, the call to
gprs_llgmm_assign is moved after the call to sgsn_mm_ctx_free. The
handling of re-used IMSIs is changed to mimic the processing of a
Detach Req.

Addresses:
<0002> gprs_gmm.c:654 MM(/f6b31ab0) Deleting old MM Context for same
    IMSI p_tmsi_old=0xc6f19134
<000f> gprs_sgsn.c:259 PDP freeing PDP context that still has a
    libgtp handle attached to it, this shouldn't happen!
[...]
SEGFAULT

Ticket: OW#1311
Sponsored-by: On-Waves ehf
This commit is contained in:
Jacob Erlbeck 2014-10-13 10:32:00 +02:00 committed by Holger Hans Peter Freyther
parent ae20b4b31b
commit 99985b5ea8
5 changed files with 84 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
openbsc/include/openbsc/gprs_sgsn.h
View File

@ -180,7 +180,8 @@ struct sgsn_pdp_ctx {
};
#define LOGPDPCTXP(level, pdp, fmt, args...) \
LOGP(DGPRS, level, "PDP(%s/%u) " fmt, (pdp)->mm->imsi, (pdp)->ti, ## args)
LOGP(DGPRS, level, "PDP(%s/%u) " \
fmt, (pdp)->mm ? (pdp)->mm->imsi : "---", (pdp)->ti, ## args)
/* look up PDP context by MM context and NSAPI */
struct sgsn_pdp_ctx *sgsn_pdp_ctx_by_nsapi(const struct sgsn_mm_ctx *mm,
@ -191,6 +192,7 @@ struct sgsn_pdp_ctx *sgsn_pdp_ctx_by_tid(const struct sgsn_mm_ctx *mm,
struct sgsn_pdp_ctx *sgsn_pdp_ctx_alloc(struct sgsn_mm_ctx *mm,
uint8_t nsapi);
void sgsn_pdp_ctx_terminate(struct sgsn_pdp_ctx *pdp);
void sgsn_pdp_ctx_free(struct sgsn_pdp_ctx *pdp);

54
openbsc/src/gprs/gprs_gmm.c
View File

@ -265,6 +265,28 @@ static void mmctx2msgid(struct msgb *msg, const struct sgsn_mm_ctx *mm)
msgb_nsei(msg) = mm->nsei;
}
static void mm_ctx_cleanup_free(struct sgsn_mm_ctx *ctx, const char *log_text)
{
struct gprs_llc_llme *llme = ctx->llme;
uint32_t tlli = ctx->tlli;
struct sgsn_pdp_ctx *pdp, *pdp2;
/* Mark MM state as deregistered */
ctx->mm_state = GMM_DEREGISTERED;
llist_for_each_entry_safe(pdp, pdp2, &ctx->pdp_list, list) {
LOGMMCTXP(LOGL_NOTICE, ctx, "Dropping PDP context for NSAPI=%u "
"due to %s\n", pdp->nsapi, log_text);
sgsn_pdp_ctx_terminate(pdp);
}
sgsn_mm_ctx_free(ctx);
ctx = NULL;
/* TLLI unassignment, must be called after sgsn_mm_ctx_free */
gprs_llgmm_assign(llme, tlli, 0xffffffff, GPRS_ALGO_GEA0, NULL);
}
/* Chapter 9.4.18 */
static int _tx_status(struct msgb *msg, uint8_t cause,
struct sgsn_mm_ctx *mmctx, int sm)
@ -603,15 +625,16 @@ static int gsm48_rx_gmm_id_resp(struct sgsn_mm_ctx *ctx, struct msgb *msg)
struct sgsn_mm_ctx *ictx;
ictx = sgsn_mm_ctx_by_imsi(mi_string);
if (ictx) {
/* Handle it like in gsm48_rx_gmm_det_req,
* except that no messages are sent to the BSS */
LOGMMCTXP(LOGL_NOTICE, ctx, "Deleting old MM Context for same IMSI "
"p_tmsi_old=0x%08x\n",
ictx->p_tmsi);
gprs_llgmm_assign(ictx->llme, ictx->tlli,
0xffffffff, GPRS_ALGO_GEA0, NULL);
/* FIXME: this is a hard free, we don't
* clean-up any PDP contexts on the
* libgtp side */
sgsn_mm_ctx_free(ictx);
ictx->mm_state = GMM_DEREGISTERED;
mm_ctx_cleanup_free(ictx, "GPRS IMSI re-use");
}
}
strncpy(ctx->imsi, mi_string, sizeof(ctx->imsi));
@ -776,7 +799,6 @@ err_inval:
static int gsm48_rx_gmm_det_req(struct sgsn_mm_ctx *ctx, struct msgb *msg)
{
struct gsm48_hdr *gh = (struct gsm48_hdr *) msgb_gmmh(msg);
struct sgsn_pdp_ctx *pdp, *pdp2;
uint8_t detach_type, power_off;
int rc;
@ -789,26 +811,10 @@ static int gsm48_rx_gmm_det_req(struct sgsn_mm_ctx *ctx, struct msgb *msg)
msgb_tlli(msg), get_value_string(gprs_det_t_mo_strs, detach_type),
power_off ? "Power-off" : "");
/* Mark MM state as deregistered */
ctx->mm_state = GMM_DEREGISTERED;
/* delete all existing PDP contexts for this MS */
llist_for_each_entry_safe(pdp, pdp2, &ctx->pdp_list, list) {
LOGMMCTXP(LOGL_NOTICE, ctx, "Dropping PDP context for NSAPI=%u "
"due to GPRS DETACH REQUEST\n", pdp->nsapi);
sgsn_delete_pdp_ctx(pdp);
/* FIXME: the callback wants to transmit a DEACT PDP CTX ACK,
* which is quite stupid for a MS that has just detached.. */
}
/* force_stby = 0 */
rc = gsm48_tx_gmm_det_ack(ctx, 0);
/* TLLI unassignment */
gprs_llgmm_assign(ctx->llme, ctx->tlli, 0xffffffff,
GPRS_ALGO_GEA0, NULL);
sgsn_mm_ctx_free(ctx);
mm_ctx_cleanup_free(ctx, "GPRS DETACH REQUEST");
return rc;
}

34
openbsc/src/gprs/gprs_sgsn.c
View File

@ -35,6 +35,7 @@
#include <openbsc/sgsn.h>
#include <openbsc/gsm_04_08_gprs.h>
#include <openbsc/gprs_gmm.h>
#include "openbsc/gprs_llc.h"
extern struct sgsn_instance *sgsn;
@ -247,11 +248,40 @@ struct sgsn_pdp_ctx *sgsn_pdp_ctx_alloc(struct sgsn_mm_ctx *mm,
}
#include <pdp.h>
/* you probably want to call sgsn_delete_pdp_ctx() instead */
/*
* This function will not trigger any GSM DEACT PDP ACK messages, so you
* probably want to call sgsn_delete_pdp_ctx() instead if the connection
* isn't detached already.
*/
void sgsn_pdp_ctx_terminate(struct sgsn_pdp_ctx *pdp)
{
OSMO_ASSERT(pdp->mm != NULL);
/* There might still be pending callbacks in libgtp. So the parts of
* this object relevant to GTP need to remain intact in this case. */
LOGPDPCTXP(LOGL_INFO, pdp, "Forcing release of PDP context\n");
/* Force the deactivation of the SNDCP layer */
sndcp_sm_deactivate_ind(&pdp->mm->llme->lle[pdp->sapi], pdp->nsapi);
/* Detach from MM context */
llist_del(&pdp->list);
pdp->mm = NULL;
sgsn_delete_pdp_ctx(pdp);
}
/*
* Don't call this function directly unless you know what you are doing.
* In normal conditions use sgsn_delete_pdp_ctx and in unspecified or
* implementation dependent abnormal ones sgsn_pdp_ctx_terminate.
*/
void sgsn_pdp_ctx_free(struct sgsn_pdp_ctx *pdp)
{
rate_ctr_group_free(pdp->ctrg);
llist_del(&pdp->list);
if (pdp->mm)
llist_del(&pdp->list);
llist_del(&pdp->g_list);
/* _if_ we still have a library handle, at least set it to NULL

22
openbsc/src/gprs/sgsn_libgtp.c
View File

@ -263,6 +263,12 @@ static int create_pdp_conf(struct pdp_t *pdp, void *cbp, int cause)
LOGPDPCTXP(LOGL_INFO, pctx, "Received CREATE PDP CTX CONF, cause=%d(%s)\n",
cause, get_value_string(gtp_cause_strs, cause));
if (!pctx->mm) {
LOGP(DGPRS, LOGL_INFO,
"No MM context, aborting CREATE PDP CTX CONF\n");
return -EIO;
}
/* Check for cause value if it was really successful */
if (cause < 0) {
LOGP(DGPRS, LOGL_NOTICE, "Create PDP ctx req timed out\n");
@ -314,16 +320,22 @@ reject:
static int delete_pdp_conf(struct pdp_t *pdp, void *cbp, int cause)
{
struct sgsn_pdp_ctx *pctx = cbp;
int rc;
int rc = 0;
LOGPDPCTXP(LOGL_INFO, pctx, "Received DELETE PDP CTX CONF, cause=%d(%s)\n",
cause, get_value_string(gtp_cause_strs, cause));
/* Deactivate the SNDCP layer */
sndcp_sm_deactivate_ind(&pctx->mm->llme->lle[pctx->sapi], pctx->nsapi);
if (pctx->mm) {
/* Deactivate the SNDCP layer */
sndcp_sm_deactivate_ind(&pctx->mm->llme->lle[pctx->sapi], pctx->nsapi);
/* Confirm deactivation of PDP context to MS */
rc = gsm48_tx_gsm_deact_pdp_acc(pctx);
/* Confirm deactivation of PDP context to MS */
rc = gsm48_tx_gsm_deact_pdp_acc(pctx);
} else {
LOGPDPCTXP(LOGL_NOTICE, pctx,
"Not deactivating SNDCP layer since the MM context "
"is not available\n");
}
/* unlink the now non-existing library handle from the pdp
* context */

3
openbsc/src/gprs/sgsn_vty.c
View File

@ -222,8 +222,9 @@ const struct value_string gprs_mm_st_strs[] = {
static void vty_dump_pdp(struct vty *vty, const char *pfx,
struct sgsn_pdp_ctx *pdp)
{
const char *imsi = pdp->mm ? pdp->mm->imsi : "(detaching)";
vty_out(vty, "%sPDP Context IMSI: %s, SAPI: %u, NSAPI: %u%s",
pfx, pdp->mm->imsi, pdp->sapi, pdp->nsapi, VTY_NEWLINE);
pfx, imsi, pdp->sapi, pdp->nsapi, VTY_NEWLINE);
vty_out(vty, "%s APN: %s%s", pfx,
gprs_apn2str(pdp->lib->apn_use.v, pdp->lib->apn_use.l),
VTY_NEWLINE);