[PATCH 5.4 31/34] sctp: leave the err path free in sctp_stream_init to sctp_stream_free

Greg Kroah-Hartman
2022-08-01T11:51:19Z

From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit 181d8d2066c000ba0a0e6940a7ad80f1a0e68e9d ]

A NULL pointer dereference was reported by Wei Chen:

BUG: kernel NULL pointer dereference, address: 0000000000000000
RIP: 0010:__list_del_entry_valid+0x26/0x80
Call Trace:
<TASK>
sctp_sched_dequeue_common+0x1c/0x90
sctp_sched_prio_dequeue+0x67/0x80
__sctp_outq_teardown+0x299/0x380
sctp_outq_free+0x15/0x20
sctp_association_free+0xc3/0x440
sctp_do_sm+0x1ca7/0x2210
sctp_assoc_bh_rcv+0x1f6/0x340

This happens when calling sctp_sendmsg without connecting to server first.
In this case, a data chunk already queues up in send queue of client side
when processing the INIT_ACK from server in sctp_process_init() where it
calls sctp_stream_init() to alloc stream_in. If it fails to alloc stream_in
all stream_out will be freed in sctp_stream_init's err path. Then in the
asoc freeing it will crash when dequeuing this data chunk as stream_out
is missing.

As we can't free stream out before dequeuing all data from send queue, and
this patch is to fix it by moving the err path stream_out/in freeing in
sctp_stream_init() to sctp_stream_free() which is eventually called when
freeing the asoc in sctp_association_free(). This fix also makes the code
in sctp_process_init() more clear.

Note that in sctp_association_init() when it fails in sctp_stream_init(),
sctp_association_free() will not be called, and in that case it should
go to 'stream_free' err path to free stream instead of 'fail_init'.

Fixes: 5bbbbe32a431 ("sctp: introduce stream scheduler foundations")
Reported-by: Wei Chen <harperchen1110@gmail.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Link: https://lore.kernel.org/r/831a3dc100c4908ff76e5bcc363be97f2778bc0b.1658787066.git.lucien.xin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sctp/associola.c | 5 ++---
net/sctp/stream.c | 19 +++----------------
2 files changed, 5 insertions(+), 19 deletions(-)

diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index fb6f62264e87..f960b0e1e552 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -224,9 +224,8 @@ static struct sctp_association *sctp_association_init(
if (!sctp_ulpq_init(&asoc->ulpq, asoc))
goto fail_init;

- if (sctp_stream_init(&asoc->stream, asoc->c.sinit_num_ostreams,
- 0, gfp))
- goto fail_init;
+ if (sctp_stream_init(&asoc->stream, asoc->c.sinit_num_ostreams, 0, gfp))
+ goto stream_free;

/* Initialize default path MTU. */
asoc->pathmtu = sp->pathmtu;
diff --git a/net/sctp/stream.c b/net/sctp/stream.c
index cd20638b6151..56762745d6e4 100644
--- a/net/sctp/stream.c
+++ b/net/sctp/stream.c
@@ -137,7 +137,7 @@ int sctp_stream_init(struct sctp_stream *stream, __u16 outcnt, __u16 incnt,

ret = sctp_stream_alloc_out(stream, outcnt, gfp);
if (ret)
- goto out_err;
+ return ret;

for (i = 0; i < stream->outcnt; i++)
SCTP_SO(stream, i)->state = SCTP_STREAM_OPEN;
@@ -145,22 +145,9 @@ int sctp_stream_init(struct sctp_stream *stream, __u16 outcnt, __u16 incnt,
handle_in:
sctp_stream_interleave_init(stream);
if (!incnt)
- goto out;
-
- ret = sctp_stream_alloc_in(stream, incnt, gfp);
- if (ret)
- goto in_err;
-
- goto out;
+ return 0;

-in_err:
- sched->free(stream);
- genradix_free(&stream->in);
-out_err:
- genradix_free(&stream->out);
- stream->outcnt = 0;
-out:
- return ret;
+ return sctp_stream_alloc_in(stream, incnt, gfp);
}

int sctp_stream_init_ext(struct sctp_stream *stream, __u16 sid)
--
2.35.1