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    Subject[PATCH 5.1 20/62] sctp: fix error handling on stream scheduler initialization
    Date
    From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

    [ Upstream commit 4d1415811e492d9a8238f8a92dd0d51612c788e9 ]

    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@syzkaller.appspotmail.com
    Fixes: 5bbbbe32a431 ("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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/sctp/stream.c | 9 ++++++++-
    1 file changed, 8 insertions(+), 1 deletion(-)

    --- a/net/sctp/stream.c
    +++ b/net/sctp/stream.c
    @@ -168,13 +168,20 @@ 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)

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