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authorXin Long <lucien.xin@gmail.com>2017-11-17 14:11:11 +0800
committerDavid S. Miller <davem@davemloft.net>2017-11-18 10:32:41 +0900
commitecca8f88da5c4260cc2bccfefd2a24976704c366 (patch)
tree763c7eece0fe70691f21ce60d1f6b3ef8e6759b5
parentd35ef8f846c72d84bfccf239c248c84f79c3a7e8 (diff)
sctp: set frag_point in sctp_setsockopt_maxseg correctly
Now in sctp_setsockopt_maxseg user_frag or frag_point can be set with val >= 8 and val <= SCTP_MAX_CHUNK_LEN. But both checks are incorrect. val >= 8 means frag_point can even be less than SCTP_DEFAULT_MINSEGMENT. Then in sctp_datamsg_from_user(), when it's value is greater than cookie echo len and trying to bundle with cookie echo chunk, the first_len will overflow. The worse case is when it's value is equal as cookie echo len, first_len becomes 0, it will go into a dead loop for fragment later on. In Hangbin syzkaller testing env, oom was even triggered due to consecutive memory allocation in that loop. Besides, SCTP_MAX_CHUNK_LEN is the max size of the whole chunk, it should deduct the data header for frag_point or user_frag check. This patch does a proper check with SCTP_DEFAULT_MINSEGMENT subtracting the sctphdr and datahdr, SCTP_MAX_CHUNK_LEN subtracting datahdr when setting frag_point via sockopt. It also improves sctp_setsockopt_maxseg codes. Suggested-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Reported-by: Hangbin Liu <liuhangbin@gmail.com> Signed-off-by: Xin Long <lucien.xin@gmail.com> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/net/sctp/sctp.h3
-rw-r--r--net/sctp/socket.c29
2 files changed, 21 insertions, 11 deletions
diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
index d7d8cba01469..749a42882437 100644
--- a/include/net/sctp/sctp.h
+++ b/include/net/sctp/sctp.h
@@ -444,7 +444,8 @@ static inline int sctp_frag_point(const struct sctp_association *asoc, int pmtu)
if (asoc->user_frag)
frag = min_t(int, frag, asoc->user_frag);
- frag = SCTP_TRUNC4(min_t(int, frag, SCTP_MAX_CHUNK_LEN));
+ frag = SCTP_TRUNC4(min_t(int, frag, SCTP_MAX_CHUNK_LEN -
+ sizeof(struct sctp_data_chunk)));
return frag;
}
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 4c0a77292792..3204a9b29407 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -3140,9 +3140,9 @@ static int sctp_setsockopt_mappedv4(struct sock *sk, char __user *optval, unsign
*/
static int sctp_setsockopt_maxseg(struct sock *sk, char __user *optval, unsigned int optlen)
{
+ struct sctp_sock *sp = sctp_sk(sk);
struct sctp_assoc_value params;
struct sctp_association *asoc;
- struct sctp_sock *sp = sctp_sk(sk);
int val;
if (optlen == sizeof(int)) {
@@ -3158,26 +3158,35 @@ static int sctp_setsockopt_maxseg(struct sock *sk, char __user *optval, unsigned
if (copy_from_user(&params, optval, optlen))
return -EFAULT;
val = params.assoc_value;
- } else
+ } else {
return -EINVAL;
+ }
- if ((val != 0) && ((val < 8) || (val > SCTP_MAX_CHUNK_LEN)))
- return -EINVAL;
+ if (val) {
+ int min_len, max_len;
- asoc = sctp_id2assoc(sk, params.assoc_id);
- if (!asoc && params.assoc_id && sctp_style(sk, UDP))
- return -EINVAL;
+ min_len = SCTP_DEFAULT_MINSEGMENT - sp->pf->af->net_header_len;
+ min_len -= sizeof(struct sctphdr) +
+ sizeof(struct sctp_data_chunk);
+
+ max_len = SCTP_MAX_CHUNK_LEN - sizeof(struct sctp_data_chunk);
+ if (val < min_len || val > max_len)
+ return -EINVAL;
+ }
+
+ asoc = sctp_id2assoc(sk, params.assoc_id);
if (asoc) {
if (val == 0) {
- val = asoc->pathmtu;
- val -= sp->pf->af->net_header_len;
+ val = asoc->pathmtu - sp->pf->af->net_header_len;
val -= sizeof(struct sctphdr) +
- sizeof(struct sctp_data_chunk);
+ sizeof(struct sctp_data_chunk);
}
asoc->user_frag = val;
asoc->frag_point = sctp_frag_point(asoc, asoc->pathmtu);
} else {
+ if (params.assoc_id && sctp_style(sk, UDP))
+ return -EINVAL;
sp->user_frag = val;
}