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sctp: fix error handling on stream scheduler initialization

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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 4ff40b8626 ("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@syzkaller.appspotmail.com
Fixes: 5bbbbe32a4 ("sctp: introduce stream scheduler foundations")
Tested-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Neil Horman <nhorman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Marcelo Ricardo Leitner 2019-06-27 19:48:10 -03:00 committed by David S. Miller
parent c8c8218ec5
commit 4d1415811e
1 changed files with 8 additions and 1 deletions
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9
net/sctp/stream.c
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@ -153,13 +153,20 @@ out:
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)