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SubjectRE: [PATCH AUTOSEL for 4.14 019/110] sctp: fix the issue that a __u16 variable may overflow in sctp_ulpq_renege
Date
From: Sasha Levin
> Sent: 03 February 2018 18:01
> [ Upstream commit 5c468674d17056148da06218d4da5d04baf22eac ]
>
> Now when reneging events in sctp_ulpq_renege(), the variable freed
> could be increased by a __u16 value twice while freed is of __u16
> type. It means freed may overflow at the second addition.
>
> This patch is to fix it by using __u32 type for 'freed', while at
> it, also to remove 'if (chunk)' check, as all renege commands are
> generated in sctp_eat_data and it can't be NULL.
>
> Reported-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.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: Sasha Levin <alexander.levin@microsoft.com>
> ---
> net/sctp/ulpqueue.c | 24 ++++++++----------------
> 1 file changed, 8 insertions(+), 16 deletions(-)
>
> diff --git a/net/sctp/ulpqueue.c b/net/sctp/ulpqueue.c
> index a71be33f3afe..e36ec5dd64c6 100644
> --- a/net/sctp/ulpqueue.c
> +++ b/net/sctp/ulpqueue.c
> @@ -1084,29 +1084,21 @@ void sctp_ulpq_partial_delivery(struct sctp_ulpq *ulpq,
> void sctp_ulpq_renege(struct sctp_ulpq *ulpq, struct sctp_chunk *chunk,
> gfp_t gfp)
> {
> - struct sctp_association *asoc;
> - __u16 needed, freed;
> -
> - asoc = ulpq->asoc;
> + struct sctp_association *asoc = ulpq->asoc;
> + __u32 freed = 0;
> + __u16 needed;
>
> - if (chunk) {
> - needed = ntohs(chunk->chunk_hdr->length);
> - needed -= sizeof(struct sctp_data_chunk);
> - } else
> - needed = SCTP_DEFAULT_MAXWINDOW;
> -
> - freed = 0;
> + needed = ntohs(chunk->chunk_hdr->length) -
> + sizeof(struct sctp_data_chunk);
>
> if (skb_queue_empty(&asoc->base.sk->sk_receive_queue)) {
> freed = sctp_ulpq_renege_order(ulpq, needed);
> - if (freed < needed) {
> + if (freed < needed)
> freed += sctp_ulpq_renege_frags(ulpq, needed - freed);
> - }
> }
> /* If able to free enough room, accept this chunk. */
> - if (chunk && (freed >= needed)) {
> - int retval;
> - retval = sctp_ulpq_tail_data(ulpq, chunk, gfp);
> + if (freed >= needed) {
> + int retval = sctp_ulpq_tail_data(ulpq, chunk, gfp);
> /*
> * Enter partial delivery if chunk has not been
> * delivered; otherwise, drain the reassembly queue.

Hmmm...
ISTM that all the maths should be done using 'unsigned int' to avoid horrid
masking operations on many cpus....

David

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