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Subject[PATCH 5.10 073/167] sctp: trim optlen when its a huge value in sctp_setsockopt
From: Xin Long <>

[ Upstream commit 2f3fdd8d4805015fa964807e1c7f3d88f31bd389 ]

After commit ca84bd058dae ("sctp: copy the optval from user space in
sctp_setsockopt"), it does memory allocation in sctp_setsockopt with
the optlen, and it would fail the allocation and return error if the
optlen from user space is a huge value.

This breaks some sockopts, like SCTP_HMAC_IDENT, SCTP_RESET_STREAMS and
SCTP_AUTH_KEY, as when processing these sockopts before, optlen would
be trimmed to a biggest value it needs when optlen is a huge value,
instead of failing the allocation and returning error.

This patch is to fix the allocation failure when it's a huge optlen from
user space by trimming it to the biggest size sctp sockopt may need when
necessary, and this biggest size is from sctp_setsockopt_reset_streams()
for SCTP_RESET_STREAMS, which is bigger than those for SCTP_HMAC_IDENT

Fixes: ca84bd058dae ("sctp: copy the optval from user space in sctp_setsockopt")
Signed-off-by: Xin Long <>
Signed-off-by: David S. Miller <>
Signed-off-by: Sasha Levin <>
net/sctp/socket.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 3ac6b21ecf2c..e872bc50bbe6 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4471,6 +4471,10 @@ static int sctp_setsockopt(struct sock *sk, int level, int optname,

if (optlen > 0) {
+ /* Trim it to the biggest size sctp sockopt may need if necessary */
+ optlen = min_t(unsigned int, optlen,
+ sizeof(__u16) * sizeof(struct sctp_reset_streams)));
kopt = memdup_sockptr(optval, optlen);
if (IS_ERR(kopt))
return PTR_ERR(kopt);

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