[PATCH net] sctp: account stream padding length for reconf chunk

From: Eiichi Tsukata <redacted>

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 <redacted>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: linux-sctp@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Greg KH <gregkh@linuxfoundation.org>
Fixes: cc16f00f6529 ("sctp: add support for generating stream reconf ssn reset request chunk")
Reported-by: Eiichi Tsukata <redacted>
Signed-off-by: Eiichi Tsukata <redacted>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Marcelo Ricardo Leitner <redacted>
---
 net/sctp/sm_make_chunk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index b8fa8f1a7277..c7503fd64915 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c

@@ -3697,7 +3697,7 @@ struct sctp_chunk *sctp_make_strreset_req(
 	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;
 

-- 
2.31.1

On Thu, Oct 14, 2021 at 4:27 AM Marcelo Ricardo Leitner
[off-list ref] wrote:

Reviewed-by: Xin Long <lucien.xin@gmail.com>

Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski [off-list ref]:

On Wed, 13 Oct 2021 17:27:29 -0300 you wrote:

From: Eiichi Tsukata <redacted>

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.

[...]

Here is the summary with links:
  - [net] sctp: account stream padding length for reconf chunk
    https://git.kernel.org/netdev/net/c/a2d859e3fc97

You are awesome, thank you!
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