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sctp: fix use-after-free in pr_debug statement
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Dmitry Vyukov reported a use-after-free in the code expanded by the
macro debug_post_sfx, which is caused by the use of the asoc pointer
after it was freed within sctp_side_effect() scope.

This patch fixes it by allowing sctp_side_effect to clear that asoc
pointer when the TCB is freed.

As Vlad explained, we also have to cover the SCTP_DISPOSITION_ABORT case
because it will trigger DELETE_TCB too on that same loop.

Also, there were places issuing SCTP_CMD_INIT_FAILED and ASSOC_FAILED
but returning SCTP_DISPOSITION_CONSUME, which would fool the scheme
above. Fix it by returning SCTP_DISPOSITION_ABORT instead.

The macro is already prepared to handle such NULL pointer.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Marcelo Ricardo Leitner authored and David S. Miller committed Jan 11, 2016
1 parent 366ce60 commit 649621e
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Showing 2 changed files with 10 additions and 18 deletions.
11 changes: 6 additions & 5 deletions net/sctp/sm_sideeffect.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -63,7 +63,7 @@ static int sctp_cmd_interpreter(sctp_event_t event_type,
static int sctp_side_effects(sctp_event_t event_type, sctp_subtype_t subtype,
sctp_state_t state,
struct sctp_endpoint *ep,
struct sctp_association *asoc,
struct sctp_association **asoc,
void *event_arg,
sctp_disposition_t status,
sctp_cmd_seq_t *commands,
Expand Down Expand Up @@ -1123,7 +1123,7 @@ int sctp_do_sm(struct net *net, sctp_event_t event_type, sctp_subtype_t subtype,
debug_post_sfn();

error = sctp_side_effects(event_type, subtype, state,
ep, asoc, event_arg, status,
ep, &asoc, event_arg, status,
&commands, gfp);
debug_post_sfx();

Expand All @@ -1136,7 +1136,7 @@ int sctp_do_sm(struct net *net, sctp_event_t event_type, sctp_subtype_t subtype,
static int sctp_side_effects(sctp_event_t event_type, sctp_subtype_t subtype,
sctp_state_t state,
struct sctp_endpoint *ep,
struct sctp_association *asoc,
struct sctp_association **asoc,
void *event_arg,
sctp_disposition_t status,
sctp_cmd_seq_t *commands,
Expand All @@ -1151,7 +1151,7 @@ static int sctp_side_effects(sctp_event_t event_type, sctp_subtype_t subtype,
* disposition SCTP_DISPOSITION_CONSUME.
*/
if (0 != (error = sctp_cmd_interpreter(event_type, subtype, state,
ep, asoc,
ep, *asoc,
event_arg, status,
commands, gfp)))
goto bail;
Expand All @@ -1174,11 +1174,12 @@ static int sctp_side_effects(sctp_event_t event_type, sctp_subtype_t subtype,
break;

case SCTP_DISPOSITION_DELETE_TCB:
case SCTP_DISPOSITION_ABORT:
/* This should now be a command. */
*asoc = NULL;
break;

case SCTP_DISPOSITION_CONSUME:
case SCTP_DISPOSITION_ABORT:
/*
* We should no longer have much work to do here as the
* real work has been done as explicit commands above.
Expand Down
17 changes: 4 additions & 13 deletions net/sctp/sm_statefuns.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2976,7 +2976,7 @@ sctp_disposition_t sctp_sf_eat_data_6_2(struct net *net,
SCTP_INC_STATS(net, SCTP_MIB_IN_DATA_CHUNK_DISCARDS);
goto discard_force;
case SCTP_IERROR_NO_DATA:
goto consume;
return SCTP_DISPOSITION_ABORT;
case SCTP_IERROR_PROTO_VIOLATION:
return sctp_sf_abort_violation(net, ep, asoc, chunk, commands,
(u8 *)chunk->subh.data_hdr, sizeof(sctp_datahdr_t));
Expand Down Expand Up @@ -3043,9 +3043,6 @@ sctp_disposition_t sctp_sf_eat_data_6_2(struct net *net,
sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SACK, force);

return SCTP_DISPOSITION_DISCARD;
consume:
return SCTP_DISPOSITION_CONSUME;

}

/*
Expand Down Expand Up @@ -3093,7 +3090,7 @@ sctp_disposition_t sctp_sf_eat_data_fast_4_4(struct net *net,
case SCTP_IERROR_BAD_STREAM:
break;
case SCTP_IERROR_NO_DATA:
goto consume;
return SCTP_DISPOSITION_ABORT;
case SCTP_IERROR_PROTO_VIOLATION:
return sctp_sf_abort_violation(net, ep, asoc, chunk, commands,
(u8 *)chunk->subh.data_hdr, sizeof(sctp_datahdr_t));
Expand All @@ -3119,7 +3116,6 @@ sctp_disposition_t sctp_sf_eat_data_fast_4_4(struct net *net,
SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));
}

consume:
return SCTP_DISPOSITION_CONSUME;
}

Expand Down Expand Up @@ -4825,9 +4821,6 @@ sctp_disposition_t sctp_sf_do_9_1_prm_abort(
* if necessary to fill gaps.
*/
struct sctp_chunk *abort = arg;
sctp_disposition_t retval;

retval = SCTP_DISPOSITION_CONSUME;

if (abort)
sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));
Expand All @@ -4845,7 +4838,7 @@ sctp_disposition_t sctp_sf_do_9_1_prm_abort(
SCTP_INC_STATS(net, SCTP_MIB_ABORTEDS);
SCTP_DEC_STATS(net, SCTP_MIB_CURRESTAB);

return retval;
return SCTP_DISPOSITION_ABORT;
}

/* We tried an illegal operation on an association which is closed. */
Expand Down Expand Up @@ -4960,12 +4953,10 @@ sctp_disposition_t sctp_sf_cookie_wait_prm_abort(
sctp_cmd_seq_t *commands)
{
struct sctp_chunk *abort = arg;
sctp_disposition_t retval;

/* Stop T1-init timer */
sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));
retval = SCTP_DISPOSITION_CONSUME;

if (abort)
sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));
Expand All @@ -4985,7 +4976,7 @@ sctp_disposition_t sctp_sf_cookie_wait_prm_abort(
sctp_add_cmd_sf(commands, SCTP_CMD_INIT_FAILED,
SCTP_PERR(SCTP_ERROR_USER_ABORT));

return retval;
return SCTP_DISPOSITION_ABORT;
}

/*
Expand Down

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