It allocates the extended area for outbound streams only on sendmsg
calls, if they are not yet allocated. When using the priority
stream scheduler, this initialization may imply into a subsequent
allocation, which may fail. In this case, it was aborting the stream
scheduler initialization but leaving the ->ext pointer (allocated) in
there, thus in a partially initialized state. On a subsequent call to
sendmsg, it would notice the ->ext pointer in there, and trip on
uninitialized stuff when trying to schedule the data chunk.
The fix is undo the ->ext initialization if the stream scheduler
initialization fails and avoid the partially initialized state.
Although syzkaller bisected this to commit 4ff40b86262b ("sctp: set
chunk transport correctly when it's a new asoc"), this bug was actually
introduced on the commit I marked below.
Reported-by: syzbot+c1a380d42b190ad1e559@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 5bbbbe32a431 ("sctp: introduce stream scheduler foundations")
Tested-by: Xin Long <lucien.xin@xxxxxxxxx>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
---
net/sctp/stream.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/net/sctp/stream.c b/net/sctp/stream.c
index 93ed07877337eace4ef7f4775dda5868359ada37..25946604af85c09917e63e5c4a8d7d6fa2caebc4 100644
--- a/net/sctp/stream.c
+++ b/net/sctp/stream.c
@@ -153,13 +153,20 @@ int sctp_stream_init(struct sctp_stream *stream, __u16 outcnt, __u16 incnt,
int sctp_stream_init_ext(struct sctp_stream *stream, __u16 sid)
{
struct sctp_stream_out_ext *soute;
+ int ret;
soute = kzalloc(sizeof(*soute), GFP_KERNEL);
if (!soute)
return -ENOMEM;
SCTP_SO(stream, sid)->ext = soute;
- return sctp_sched_init_sid(stream, sid, GFP_KERNEL);
+ ret = sctp_sched_init_sid(stream, sid, GFP_KERNEL);
+ if (ret) {
+ kfree(SCTP_SO(stream, sid)->ext);
+ SCTP_SO(stream, sid)->ext = NULL;
+ }
+
+ return ret;
}
void sctp_stream_free(struct sctp_stream *stream)
--
2.21.0
