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| author | Xin Long <lucien.xin@gmail.com> | 2017-11-17 14:11:11 +0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-11-18 10:32:41 +0900 |
| commit | ecca8f88da5c4260cc2bccfefd2a24976704c366 (patch) | |
| tree | 763c7eece0fe70691f21ce60d1f6b3ef8e6759b5 /include | |
| parent | d35ef8f846c72d84bfccf239c248c84f79c3a7e8 (diff) | |
| download | linux-ecca8f88da5c4260cc2bccfefd2a24976704c366.tar.bz2 | |
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>
Diffstat (limited to 'include')
| -rw-r--r-- | include/net/sctp/sctp.h | 3 |
1 files changed, 2 insertions, 1 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; } |