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Message-Id: <51dffdfdb37c240ff7e9b0b2a93433f217fa4d2c.1452257700.git.marcelo.leitner@gmail.com>
Date: Fri, 8 Jan 2016 11:00:54 -0200
From: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To: netdev@...r.kernel.org
Cc: linux-sctp@...r.kernel.org, dvyukov@...gle.com,
vyasevich@...il.com, eric.dumazet@...il.com,
syzkaller@...glegroups.com, kcc@...gle.com, glider@...gle.com,
sasha.levin@...cle.com
Subject: [PATCH] sctp: fix use-after-free in pr_debug statement
Couldn't get syzkaller working over here, so I still need your help on
testing this. I expect this will be the last cycle, though.
If it does generate another trace, I'll need the reproducer too because
I can't find anything else just with code review.
Thanks
--8<--
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@...gle.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
---
net/sctp/sm_sideeffect.c | 11 ++++++-----
net/sctp/sm_statefuns.c | 17 ++++-------------
2 files changed, 10 insertions(+), 18 deletions(-)
diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
index 4f170ad38ff4f7d345d8e3a3fee7d691df64d9cb..2e21384697c2a6a5fd045142bcd9c39992d3867f 100644
--- a/net/sctp/sm_sideeffect.c
+++ b/net/sctp/sm_sideeffect.c
@@ -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,
@@ -1125,7 +1125,7 @@ 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();
@@ -1138,7 +1138,7 @@ 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,
@@ -1153,7 +1153,7 @@ 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;
@@ -1176,11 +1176,12 @@ 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.
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index 22c2bf367d7e8c7025065f33eabfd7e93a7f4021..f1f08c8f277bd8719299d1ed21eb23e36d55f7e2 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -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));
@@ -3043,9 +3043,6 @@ discard_noforce:
sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SACK, force);
return SCTP_DISPOSITION_DISCARD;
-consume:
- return SCTP_DISPOSITION_CONSUME;
-
}
/*
@@ -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));
@@ -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;
}
@@ -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));
@@ -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. */
@@ -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));
@@ -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;
}
/*
--
2.5.0
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