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Subject[PATCH 4.20 304/352] sctp: check and update stream->out_curr when allocating stream_out
Date
4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

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

[ Upstream commit cfe4bd7a257f6d6f81d3458d8c9d9ec4957539e6 ]

Now when using stream reconfig to add out streams, stream->out
will get re-allocated, and all old streams' information will
be copied to the new ones and the old ones will be freed.

So without stream->out_curr updated, next time when trying to
send from stream->out_curr stream, a panic would be caused.

This patch is to check and update stream->out_curr when
allocating stream_out.

v1->v2:
- define fa_index() to get elem index from stream->out_curr.
v2->v3:
- repost with no change.

Fixes: 5bbbbe32a431 ("sctp: introduce stream scheduler foundations")
Reported-by: Ying Xu <yinxu@redhat.com>
Reported-by: syzbot+e33a3a138267ca119c7d@syzkaller.appspotmail.com
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sctp/stream.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

--- a/net/sctp/stream.c
+++ b/net/sctp/stream.c
@@ -84,6 +84,19 @@ static void fa_zero(struct flex_array *f
}
}

+static size_t fa_index(struct flex_array *fa, void *elem, size_t count)
+{
+ size_t index = 0;
+
+ while (count--) {
+ if (elem == flex_array_get(fa, index))
+ break;
+ index++;
+ }
+
+ return index;
+}
+
/* Migrates chunks from stream queues to new stream queues if needed,
* but not across associations. Also, removes those chunks to streams
* higher than the new max.
@@ -147,6 +160,13 @@ static int sctp_stream_alloc_out(struct

if (stream->out) {
fa_copy(out, stream->out, 0, min(outcnt, stream->outcnt));
+ if (stream->out_curr) {
+ size_t index = fa_index(stream->out, stream->out_curr,
+ stream->outcnt);
+
+ BUG_ON(index == stream->outcnt);
+ stream->out_curr = flex_array_get(out, index);
+ }
fa_free(stream->out);
}


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