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osmo-sgsn
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SGSN: Code to help debug / fix sgsn crash in cb_data_ind() 

A crash was obsserved in cb_data_ind() when mm is dereferenced.

This patch adds some safeguards that try to prevent the library handle
back-pointer to the pdp_ctx to be NULL, and print a stack backtrace in
case we are free() ing the sgsn-side pdp_ctx while there's still a
library handle attached.
This commit is contained in:
Harald Welte 2012-07-14 12:15:19 +02:00
parent 7b022eed2d
commit fdf453c0a9
2 changed files with 26 additions and 1 deletions
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15
openbsc/src/gprs/gprs_sgsn.c
View File

@ -25,6 +25,7 @@
#include <osmocom/core/talloc.h>
#include <osmocom/core/timer.h>
#include <osmocom/core/rate_ctr.h>
#include <osmocom/core/backtrace.h>
#include <osmocom/gprs/gprs_ns.h>
#include <osmocom/gprs/gprs_bssgp.h>
@ -240,12 +241,26 @@ struct sgsn_pdp_ctx *sgsn_pdp_ctx_alloc(struct sgsn_mm_ctx *mm,
return pdp;
}
#include <pdp.h>
/* you probably want to call sgsn_delete_pdp_ctx() instead */
void sgsn_pdp_ctx_free(struct sgsn_pdp_ctx *pdp)
{
rate_ctr_group_free(pdp->ctrg);
llist_del(&pdp->list);
llist_del(&pdp->g_list);
/* _if_ we still have a library handle, at least set it to NULL
* to avoid any dereferences of the now-deleted PDP context from
* sgsn_libgtp:cb_data_ind() */
if (pdp->lib) {
struct pdp_t *lib = pdp->lib;
LOGP(DGPRS, LOGL_NOTICE, "freeing PDP context that still "
"has a libgtp handle attached to it, this shouldn't "
"happen!\n");
osmo_generate_backtrace();
lib->priv = NULL;
}
talloc_free(pdp);
}

12
openbsc/src/gprs/sgsn_libgtp.c
View File

@ -317,6 +317,10 @@ static int delete_pdp_conf(struct pdp_t *pdp, void *cbp, int cause)
/* Confirm deactivation of PDP context to MS */
rc = gsm48_tx_gsm_deact_pdp_acc(pctx);
/* unlink the now non-existing library handle from the pdp
* context */
pctx->lib = NULL;
sgsn_pdp_ctx_free(pctx);
return rc;
@ -422,10 +426,16 @@ static int cb_data_ind(struct pdp_t *lib, void *packet, unsigned int len)
pdp = lib->priv;
if (!pdp) {
DEBUGP(DGPRS, "GTP DATA IND from GGSN for unknown PDP\n");
LOGP(DGPRS, LOGL_NOTICE,
"GTP DATA IND from GGSN for unknown PDP\n");
return -EIO;
}
mm = pdp->mm;
if (!mm) {
LOGP(DGPRS, LOGL_ERROR,
"PDP context (imsi=%s) without MM context!\n", mm->imsi);
return -EIO;
}
msg = msgb_alloc_headroom(len+256, 128, "GTP->SNDCP");
ud = msgb_put(msg, len);