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Add reference counts for inp/stcb/net when timers are running.

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This avoids a use-after-free reported for the userland stack.
Thanks to Taylor Brandstetter for suggesting a patch for
the userland stack.

MFC after:		1 week
This commit is contained in:
tuexen 2020-07-19 12:34:19 +00:00
parent 3e67e9ff36
commit 66a7065c4c
5 changed files with 153 additions and 82 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
sys/netinet/sctp_os_bsd.h
View File

@ -269,12 +269,17 @@ typedef struct callout sctp_os_timer_t;
#define SCTP_OS_TIMER_INIT(tmr) callout_init(tmr, 1)
#define SCTP_OS_TIMER_START callout_reset
#define SCTP_OS_TIMER_STOP callout_stop
#define SCTP_OS_TIMER_STOP_DRAIN callout_drain
#define SCTP_OS_TIMER_PENDING callout_pending
#define SCTP_OS_TIMER_ACTIVE callout_active
#define SCTP_OS_TIMER_DEACTIVATE callout_deactivate
/*
* NOTE: The next two shouldn't be called directly outside of sctp_timer_start()
* and sctp_timer_stop(), since they don't handle incrementing/decrementing
* relevant reference counts.
*/
#define SCTP_OS_TIMER_START callout_reset
#define SCTP_OS_TIMER_STOP callout_stop
#define SCTP_OS_TIMER_STOP_DRAIN callout_drain
#define SCTP_OS_TIMER_PENDING callout_pending
#define SCTP_OS_TIMER_ACTIVE callout_active
#define SCTP_OS_TIMER_DEACTIVATE callout_deactivate
#define sctp_get_tick_count() (ticks)

73
sys/netinet/sctp_pcb.c
View File

@ -2739,23 +2739,54 @@ sctp_move_pcb_and_assoc(struct sctp_inpcb *old_inp, struct sctp_inpcb *new_inp,
}
}
}
/*
* Now any running timers need to be adjusted since we really don't
* care if they are running or not just blast in the new_inp into
* all of them.
*/
stcb->asoc.dack_timer.ep = (void *)new_inp;
stcb->asoc.asconf_timer.ep = (void *)new_inp;
stcb->asoc.strreset_timer.ep = (void *)new_inp;
stcb->asoc.shut_guard_timer.ep = (void *)new_inp;
stcb->asoc.autoclose_timer.ep = (void *)new_inp;
stcb->asoc.delete_prim_timer.ep = (void *)new_inp;
/* Now any running timers need to be adjusted. */
if (stcb->asoc.dack_timer.ep == old_inp) {
SCTP_INP_DECR_REF(old_inp);
stcb->asoc.dack_timer.ep = new_inp;
SCTP_INP_INCR_REF(new_inp);
}
if (stcb->asoc.asconf_timer.ep == old_inp) {
SCTP_INP_DECR_REF(old_inp);
stcb->asoc.asconf_timer.ep = new_inp;
SCTP_INP_INCR_REF(new_inp);
}
if (stcb->asoc.strreset_timer.ep == old_inp) {
SCTP_INP_DECR_REF(old_inp);
stcb->asoc.strreset_timer.ep = new_inp;
SCTP_INP_INCR_REF(new_inp);
}
if (stcb->asoc.shut_guard_timer.ep == old_inp) {
SCTP_INP_DECR_REF(old_inp);
stcb->asoc.shut_guard_timer.ep = new_inp;
SCTP_INP_INCR_REF(new_inp);
}
if (stcb->asoc.autoclose_timer.ep == old_inp) {
SCTP_INP_DECR_REF(old_inp);
stcb->asoc.autoclose_timer.ep = new_inp;
SCTP_INP_INCR_REF(new_inp);
}
if (stcb->asoc.delete_prim_timer.ep == old_inp) {
SCTP_INP_DECR_REF(old_inp);
stcb->asoc.delete_prim_timer.ep = new_inp;
SCTP_INP_INCR_REF(new_inp);
}
/* now what about the nets? */
TAILQ_FOREACH(net, &stcb->asoc.nets, sctp_next) {
net->pmtu_timer.ep = (void *)new_inp;
net->hb_timer.ep = (void *)new_inp;
net->rxt_timer.ep = (void *)new_inp;
if (net->pmtu_timer.ep == old_inp) {
SCTP_INP_DECR_REF(old_inp);
net->pmtu_timer.ep = new_inp;
SCTP_INP_INCR_REF(new_inp);
}
if (net->hb_timer.ep == old_inp) {
SCTP_INP_DECR_REF(old_inp);
net->hb_timer.ep = new_inp;
SCTP_INP_INCR_REF(new_inp);
}
if (net->rxt_timer.ep == old_inp) {
SCTP_INP_DECR_REF(old_inp);
net->rxt_timer.ep = new_inp;
SCTP_INP_INCR_REF(new_inp);
}
}
SCTP_INP_WUNLOCK(new_inp);
SCTP_INP_WUNLOCK(old_inp);
@ -3562,7 +3593,7 @@ sctp_inpcb_free(struct sctp_inpcb *inp, int immediate, int from)
being_refed++;
if (SCTP_ASOC_CREATE_LOCK_CONTENDED(inp))
being_refed++;
/* NOTE: 0 refcount also means no timers are referencing us. */
if ((inp->refcount) ||
(being_refed) ||
(inp->sctp_flags & SCTP_PCB_FLAGS_CLOSE_IP)) {
@ -3584,16 +3615,6 @@ sctp_inpcb_free(struct sctp_inpcb *inp, int immediate, int from)
SCTP_INP_WUNLOCK(inp);
SCTP_ASOC_CREATE_UNLOCK(inp);
SCTP_INP_INFO_WUNLOCK();
/*
* Now we release all locks. Since this INP cannot be found anymore
* except possibly by the kill timer that might be running. We call
* the drain function here. It should hit the case were it sees the
* ACTIVE flag cleared and exit out freeing us to proceed and
* destroy everything.
*/
if (from != SCTP_CALLED_FROM_INPKILL_TIMER) {
(void)SCTP_OS_TIMER_STOP_DRAIN(&inp->sctp_ep.signature_change.timer);
}
#ifdef SCTP_LOG_CLOSING
sctp_log_closing(inp, NULL, 5);

1
sys/netinet/sctp_var.h
View File

@ -186,7 +186,6 @@ extern struct pr_usrreqs sctp_usrreqs;
#define sctp_free_remote_addr(__net) { \
if ((__net)) { \
if (SCTP_DECREMENT_AND_CHECK_REFCOUNT(&(__net)->ref_count)) { \
(void)SCTP_OS_TIMER_STOP(&(__net)->rxt_timer.timer); \
RO_NHFREE(&(__net)->ro); \
if ((__net)->src_addr_selected) { \
sctp_free_ifa((__net)->ro._s_addr); \

136
sys/netinet/sctputil.c
View File

@ -1713,16 +1713,22 @@ sctp_timeout_handler(void *t)
struct sctp_nets *net;
struct sctp_timer *tmr;
struct mbuf *op_err;
int did_output;
int type;
int i, secret;
bool did_output, released_asoc_reference;
/*
* If inp, stcb or net are not NULL, then references to these were
* added when the timer was started, and must be released before
* this function returns.
*/
tmr = (struct sctp_timer *)t;
inp = (struct sctp_inpcb *)tmr->ep;
stcb = (struct sctp_tcb *)tmr->tcb;
net = (struct sctp_nets *)tmr->net;
CURVNET_SET((struct vnet *)tmr->vnet);
did_output = 1;
released_asoc_reference = false;
#ifdef SCTP_AUDITING_ENABLED
sctp_audit_log(0xF0, (uint8_t)tmr->type);
@ -1738,56 +1744,39 @@ sctp_timeout_handler(void *t)
KASSERT(stcb == NULL || stcb->sctp_ep == inp,
("sctp_timeout_handler of type %d: inp = %p, stcb->sctp_ep %p",
type, stcb, stcb->sctp_ep));
if (inp) {
SCTP_INP_INCR_REF(inp);
}
tmr->stopped_from = 0xa001;
if (stcb) {
atomic_add_int(&stcb->asoc.refcnt, 1);
if (stcb->asoc.state == 0) {
atomic_add_int(&stcb->asoc.refcnt, -1);
if (inp) {
SCTP_INP_DECR_REF(inp);
}
SCTPDBG(SCTP_DEBUG_TIMER2,
"Timer type %d handler exiting due to CLOSED association.\n",
type);
CURVNET_RESTORE();
return;
}
if ((stcb != NULL) && (stcb->asoc.state == SCTP_STATE_EMPTY)) {
SCTPDBG(SCTP_DEBUG_TIMER2,
"Timer type %d handler exiting due to CLOSED association.\n",
type);
goto out_decr;
}
tmr->stopped_from = 0xa002;
SCTPDBG(SCTP_DEBUG_TIMER2, "Timer type %d goes off.\n", type);
if (!SCTP_OS_TIMER_ACTIVE(&tmr->timer)) {
if (inp) {
SCTP_INP_DECR_REF(inp);
}
if (stcb) {
atomic_add_int(&stcb->asoc.refcnt, -1);
}
SCTPDBG(SCTP_DEBUG_TIMER2,
"Timer type %d handler exiting due to not being active.\n",
type);
CURVNET_RESTORE();
return;
goto out_decr;
}
tmr->stopped_from = 0xa003;
if (stcb) {
SCTP_TCB_LOCK(stcb);
/*
* Release reference so that association can be freed if
* necessary below. This is safe now that we have acquired
* the lock.
*/
atomic_add_int(&stcb->asoc.refcnt, -1);
released_asoc_reference = true;
if ((type != SCTP_TIMER_TYPE_ASOCKILL) &&
((stcb->asoc.state == 0) ||
((stcb->asoc.state == SCTP_STATE_EMPTY) ||
(stcb->asoc.state & SCTP_STATE_ABOUT_TO_BE_FREED))) {
SCTP_TCB_UNLOCK(stcb);
if (inp) {
SCTP_INP_DECR_REF(inp);
}
SCTPDBG(SCTP_DEBUG_TIMER2,
"Timer type %d handler exiting due to CLOSED association.\n",
type);
CURVNET_RESTORE();
return;
goto out;
}
} else if (inp != NULL) {
SCTP_INP_WLOCK(inp);
@ -1803,13 +1792,13 @@ sctp_timeout_handler(void *t)
/*
* Callout has been rescheduled.
*/
goto get_out;
goto out;
}
if (!SCTP_OS_TIMER_ACTIVE(&tmr->timer)) {
/*
* Not active, so no action.
*/
goto get_out;
goto out;
}
SCTP_OS_TIMER_DEACTIVATE(&tmr->timer);
@ -1836,6 +1825,7 @@ sctp_timeout_handler(void *t)
sctp_auditing(4, inp, stcb, net);
#endif
sctp_chunk_output(inp, stcb, SCTP_OUTPUT_FROM_T3, SCTP_SO_NOT_LOCKED);
did_output = true;
if ((stcb->asoc.num_send_timers_up == 0) &&
(stcb->asoc.sent_queue_cnt > 0)) {
struct sctp_tmit_chunk *chk;
@ -1866,8 +1856,7 @@ sctp_timeout_handler(void *t)
/* no need to unlock on tcb its gone */
goto out_decr;
}
/* We do output but not here */
did_output = 0;
did_output = false;
break;
case SCTP_TIMER_TYPE_RECV:
KASSERT(inp != NULL && stcb != NULL && net == NULL,
@ -1880,6 +1869,7 @@ sctp_timeout_handler(void *t)
sctp_auditing(4, inp, stcb, NULL);
#endif
sctp_chunk_output(inp, stcb, SCTP_OUTPUT_FROM_SACK_TMR, SCTP_SO_NOT_LOCKED);
did_output = true;
break;
case SCTP_TIMER_TYPE_SHUTDOWN:
KASSERT(inp != NULL && stcb != NULL && net != NULL,
@ -1895,6 +1885,7 @@ sctp_timeout_handler(void *t)
sctp_auditing(4, inp, stcb, net);
#endif
sctp_chunk_output(inp, stcb, SCTP_OUTPUT_FROM_SHUT_TMR, SCTP_SO_NOT_LOCKED);
did_output = true;
break;
case SCTP_TIMER_TYPE_HEARTBEAT:
KASSERT(inp != NULL && stcb != NULL && net != NULL,
@ -1912,6 +1903,9 @@ sctp_timeout_handler(void *t)
if (!(net->dest_state & SCTP_ADDR_NOHB)) {
sctp_timer_start(SCTP_TIMER_TYPE_HEARTBEAT, inp, stcb, net);
sctp_chunk_output(inp, stcb, SCTP_OUTPUT_FROM_HB_TMR, SCTP_SO_NOT_LOCKED);
did_output = true;
} else {
did_output = false;
}
break;
case SCTP_TIMER_TYPE_COOKIE:
@ -1932,6 +1926,7 @@ sctp_timeout_handler(void *t)
* respect to where from in chunk_output.
*/
sctp_chunk_output(inp, stcb, SCTP_OUTPUT_FROM_T3, SCTP_SO_NOT_LOCKED);
did_output = true;
break;
case SCTP_TIMER_TYPE_NEWCOOKIE:
KASSERT(inp != NULL && stcb == NULL && net == NULL,
@ -1953,7 +1948,7 @@ sctp_timeout_handler(void *t)
sctp_select_initial_TSN(&inp->sctp_ep);
}
sctp_timer_start(SCTP_TIMER_TYPE_NEWCOOKIE, inp, NULL, NULL);
did_output = 0;
did_output = false;
break;
case SCTP_TIMER_TYPE_PATHMTURAISE:
KASSERT(inp != NULL && stcb != NULL && net != NULL,
@ -1961,7 +1956,7 @@ sctp_timeout_handler(void *t)
type, inp, stcb, net));
SCTP_STAT_INCR(sctps_timopathmtu);
sctp_pathmtu_timer(inp, stcb, net);
did_output = 0;
did_output = false;
break;
case SCTP_TIMER_TYPE_SHUTDOWNACK:
KASSERT(inp != NULL && stcb != NULL && net != NULL,
@ -1977,6 +1972,7 @@ sctp_timeout_handler(void *t)
sctp_auditing(4, inp, stcb, net);
#endif
sctp_chunk_output(inp, stcb, SCTP_OUTPUT_FROM_SHUT_ACK_TMR, SCTP_SO_NOT_LOCKED);
did_output = true;
break;
case SCTP_TIMER_TYPE_ASCONF:
KASSERT(inp != NULL && stcb != NULL && net != NULL,
@ -1991,6 +1987,7 @@ sctp_timeout_handler(void *t)
sctp_auditing(4, inp, stcb, net);
#endif
sctp_chunk_output(inp, stcb, SCTP_OUTPUT_FROM_ASCONF_TMR, SCTP_SO_NOT_LOCKED);
did_output = true;
break;
case SCTP_TIMER_TYPE_SHUTDOWNGUARD:
KASSERT(inp != NULL && stcb != NULL && net == NULL,
@ -2000,6 +1997,7 @@ sctp_timeout_handler(void *t)
op_err = sctp_generate_cause(SCTP_BASE_SYSCTL(sctp_diag_info_code),
"Shutdown guard timer expired");
sctp_abort_an_association(inp, stcb, op_err, SCTP_SO_NOT_LOCKED);
did_output = true;
/* no need to unlock on tcb its gone */
goto out_decr;
case SCTP_TIMER_TYPE_AUTOCLOSE:
@ -2009,7 +2007,7 @@ sctp_timeout_handler(void *t)
SCTP_STAT_INCR(sctps_timoautoclose);
sctp_autoclose_timer(inp, stcb);
sctp_chunk_output(inp, stcb, SCTP_OUTPUT_FROM_AUTOCLOSE_TMR, SCTP_SO_NOT_LOCKED);
did_output = 0;
did_output = true;
break;
case SCTP_TIMER_TYPE_STRRESET:
KASSERT(inp != NULL && stcb != NULL && net == NULL,
@ -2021,6 +2019,7 @@ sctp_timeout_handler(void *t)
goto out_decr;
}
sctp_chunk_output(inp, stcb, SCTP_OUTPUT_FROM_STRRST_TMR, SCTP_SO_NOT_LOCKED);
did_output = true;
break;
case SCTP_TIMER_TYPE_INPKILL:
KASSERT(inp != NULL && stcb == NULL && net == NULL,
@ -2061,6 +2060,7 @@ sctp_timeout_handler(void *t)
("timeout of type %d: inp = %p, stcb = %p, net = %p",
type, inp, stcb, net));
sctp_handle_addr_wq();
did_output = true;
break;
case SCTP_TIMER_TYPE_PRIM_DELETED:
KASSERT(inp != NULL && stcb != NULL && net == NULL,
@ -2068,20 +2068,22 @@ sctp_timeout_handler(void *t)
type, inp, stcb, net));
SCTP_STAT_INCR(sctps_timodelprim);
sctp_delete_prim_timer(inp, stcb);
did_output = false;
break;
default:
#ifdef INVARIANTS
panic("Unknown timer type %d", type);
#else
goto get_out;
did_output = false;
goto out;
#endif
}
#ifdef SCTP_AUDITING_ENABLED
sctp_audit_log(0xF1, (uint8_t)type);
if (inp)
if (inp != NULL)
sctp_auditing(5, inp, stcb, net);
#endif
if ((did_output) && stcb) {
if (did_output && (stcb != NULL)) {
/*
* Now we need to clean up the control chunk chain if an
* ECNE is on it. It must be marked as UNSENT again so next
@ -2091,8 +2093,8 @@ sctp_timeout_handler(void *t)
*/
sctp_fix_ecn_echo(&stcb->asoc);
}
get_out:
if (stcb) {
out:
if (stcb != NULL) {
SCTP_TCB_UNLOCK(stcb);
} else if (inp != NULL) {
SCTP_INP_WUNLOCK(inp);
@ -2101,10 +2103,16 @@ sctp_timeout_handler(void *t)
}
out_decr:
if (inp) {
/* These reference counts were incremented in sctp_timer_start(). */
if (inp != NULL) {
SCTP_INP_DECR_REF(inp);
}
if ((stcb != NULL) && !released_asoc_reference) {
atomic_add_int(&stcb->asoc.refcnt, -1);
}
if (net != NULL) {
sctp_free_remote_addr(net);
}
out_no_decr:
SCTPDBG(SCTP_DEBUG_TIMER2, "Timer type %d handler finished.\n", type);
CURVNET_RESTORE();
@ -2538,6 +2546,19 @@ sctp_timer_start(int t_type, struct sctp_inpcb *inp, struct sctp_tcb *stcb,
SCTPDBG(SCTP_DEBUG_TIMER2,
"Timer type %d started: ticks=%u, inp=%p, stcb=%p, net=%p.\n",
t_type, to_ticks, inp, stcb, net);
/*
* If this is a newly scheduled callout, as opposed to a
* rescheduled one, increment relevant reference counts.
*/
if (tmr->ep != NULL) {
SCTP_INP_INCR_REF(inp);
}
if (tmr->tcb != NULL) {
atomic_add_int(&stcb->asoc.refcnt, 1);
}
if (tmr->net != NULL) {
atomic_add_int(&net->ref_count, 1);
}
} else {
/*
* This should not happen, since we checked for pending
@ -2830,9 +2851,26 @@ sctp_timer_stop(int t_type, struct sctp_inpcb *inp, struct sctp_tcb *stcb,
SCTPDBG(SCTP_DEBUG_TIMER2,
"Timer type %d stopped: inp=%p, stcb=%p, net=%p.\n",
t_type, inp, stcb, net);
tmr->ep = NULL;
tmr->tcb = NULL;
tmr->net = NULL;
/*
* If the timer was actually stopped, decrement reference
* counts that were incremented in sctp_timer_start().
*/
if (tmr->ep != NULL) {
SCTP_INP_DECR_REF(inp);
tmr->ep = NULL;
}
if (tmr->tcb != NULL) {
atomic_add_int(&stcb->asoc.refcnt, -1);
tmr->tcb = NULL;
}
if (tmr->net != NULL) {
/*
* Can't use net, since it doesn't work for
* SCTP_TIMER_TYPE_ASCONF.
*/
sctp_free_remote_addr((struct sctp_nets *)tmr->net);
tmr->net = NULL;
}
} else {
SCTPDBG(SCTP_DEBUG_TIMER2,
"Timer type %d not stopped: inp=%p, stcb=%p, net=%p.\n",

8
sys/netinet/sctputil.h
View File

@ -90,6 +90,14 @@ sctp_notify_stream_reset_add(struct sctp_tcb *stcb, uint16_t numberin,
void
sctp_notify_stream_reset_tsn(struct sctp_tcb *stcb, uint32_t sending_tsn, uint32_t recv_tsn, int flag);
/*
* NOTE: sctp_timer_start() will increment the reference count of any relevant
* structure the timer is referencing, in order to prevent a race condition
* between the timer executing and the structure being freed.
*
* When the timer fires or sctp_timer_stop() is called, these references are
* removed.
*/
void
sctp_timer_start(int, struct sctp_inpcb *, struct sctp_tcb *,
struct sctp_nets *);