[PATCH 4.19 33/50] sctp: account stream padding length for reconf chunk

[Greg Kroah-Hartman]

From: Eiichi Tsukata <eiichi.tsukata@xxxxxxxxxxx>

commit a2d859e3fc97e79d907761550dbc03ff1b36479c upstream.

sctp_make_strreset_req() makes repeated calls to sctp_addto_chunk()
which will automatically account for padding on each call. inreq and
outreq are already 4 bytes aligned, but the payload is not and doing
SCTP_PAD4(a + b) (which _sctp_make_chunk() did implicitly here) is
different from SCTP_PAD4(a) + SCTP_PAD4(b) and not enough. It led to
possible attempt to use more buffer than it was allocated and triggered
a BUG_ON.

Cc: Vlad Yasevich <vyasevich@xxxxxxxxx>
Cc: Neil Horman <nhorman@xxxxxxxxxxxxx>
Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
Fixes: cc16f00f6529 ("sctp: add support for generating stream reconf ssn reset request chunk")
Reported-by: Eiichi Tsukata <eiichi.tsukata@xxxxxxxxxxx>
Signed-off-by: Eiichi Tsukata <eiichi.tsukata@xxxxxxxxxxx>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Signed-off-by: Marcelo Ricardo Leitner <mleitner@xxxxxxxxxx>
Reviewed-by: Xin Long <lucien.xin@xxxxxxxxx>
Link: https://lore.kernel.org/r/b97c1f8b0c7ff79ac4ed206fc2c49d3612e0850c.1634156849.git.mleitner@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/sctp/sm_make_chunk.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -3673,7 +3673,7 @@ struct sctp_chunk *sctp_make_strreset_re
 	outlen = (sizeof(outreq) + stream_len) * out;
 	inlen = (sizeof(inreq) + stream_len) * in;
 
-	retval = sctp_make_reconf(asoc, outlen + inlen);
+	retval = sctp_make_reconf(asoc, SCTP_PAD4(outlen) + SCTP_PAD4(inlen));
 	if (!retval)
 		return NULL;