From: Jakub Audykowicz jakub.audykowicz@gmail.com
[ Upstream commit afd0a8006e98b1890908f81746c94ca5dae29d7c ]
If for some reason an association's fragmentation point is zero, sctp_datamsg_from_user will try to endlessly try to divide a message into zero-sized chunks. This eventually causes kernel panic due to running out of memory.
Although this situation is quite unlikely, it has occurred before as reported. I propose to add this simple last-ditch sanity check due to the severity of the potential consequences.
Signed-off-by: Jakub Audykowicz jakub.audykowicz@gmail.com Acked-by: Neil Horman nhorman@tuxdriver.com Acked-by: Marcelo Ricardo Leitner marcelo.leitner@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/sctp/sctp.h | 5 +++++ net/sctp/chunk.c | 6 ++++++ net/sctp/socket.c | 3 +-- 3 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h index ab9242e51d9e0..2abbc15824af9 100644 --- a/include/net/sctp/sctp.h +++ b/include/net/sctp/sctp.h @@ -620,4 +620,9 @@ static inline bool sctp_transport_pmtu_check(struct sctp_transport *t) return false; }
+static inline __u32 sctp_min_frag_point(struct sctp_sock *sp, __u16 datasize) +{ + return sctp_mtu_payload(sp, SCTP_DEFAULT_MINSEGMENT, datasize); +} + #endif /* __net_sctp_h__ */ diff --git a/net/sctp/chunk.c b/net/sctp/chunk.c index ce8087846f059..d2048de86e7c2 100644 --- a/net/sctp/chunk.c +++ b/net/sctp/chunk.c @@ -191,6 +191,12 @@ struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc, * the packet */ max_data = asoc->frag_point; + if (unlikely(!max_data)) { + max_data = sctp_min_frag_point(sctp_sk(asoc->base.sk), + sctp_datachk_len(&asoc->stream)); + pr_warn_ratelimited("%s: asoc:%p frag_point is zero, forcing max_data to default minimum (%Zu)", + __func__, asoc, max_data); + }
/* If the the peer requested that we authenticate DATA chunks * we need to account for bundling of the AUTH chunks along with diff --git a/net/sctp/socket.c b/net/sctp/socket.c index e7a11cd7633f5..95f9068b85497 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -3328,8 +3328,7 @@ static int sctp_setsockopt_maxseg(struct sock *sk, char __user *optval, unsigned __u16 datasize = asoc ? sctp_datachk_len(&asoc->stream) : sizeof(struct sctp_data_chunk);
- min_len = sctp_mtu_payload(sp, SCTP_DEFAULT_MINSEGMENT, - datasize); + min_len = sctp_min_frag_point(sp, datasize); max_len = SCTP_MAX_CHUNK_LEN - datasize;
if (val < min_len || val > max_len)