[PATCH net 0/3] Some sockopt optlen fixes

[PATCH net 0/3] Some sockopt optlen fixes

[Marcelo Ricardo Leitner]

Hangbin Liu reported that some SCTP sockopt are allowing the user to get
the kernel to allocate really large buffers by not having a ceiling on
optlen.

This patchset address this issue (in patch 2), replace an GFP_ATOMIC
that isn't needed and avoid calculating the option size multiple times
in some setsockopt.

Marcelo Ricardo Leitner (3):
  sctp: GFP_ATOMIC is not needed in sctp_setsockopt_events
  sctp: add a ceiling to optlen in some sockopts
  sctp: make use of pre-calculated len

 net/sctp/socket.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

-- 
2.14.3

[PATCH net 1/3] sctp: GFP_ATOMIC is not needed in sctp_setsockopt_events

[Marcelo Ricardo Leitner]

So replace it with GFP_USER and also add __GFP_NOWARN.

Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
---
 net/sctp/socket.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index b4fb6e4886d264f302fc67b8d822cd8bdb5f3f41..54c046783a89e76c9909ee85c83e6be38ada41a7 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -2277,7 +2277,7 @@ static int sctp_setsockopt_events(struct sock *sk, char __user *optval,
 
 		if (asoc && sctp_outq_is_empty(&asoc->outqueue)) {
 			event = sctp_ulpevent_make_sender_dry_event(asoc,
-					GFP_ATOMIC);
+					GFP_USER | __GFP_NOWARN);
 			if (!event)
 				return -ENOMEM;
 
-- 
2.14.3

[PATCH net 2/3] sctp: add a ceiling to optlen in some sockopts

[Marcelo Ricardo Leitner]

Hangbin Liu reported that some sockopt calls could cause the kernel to log
a warning on memory allocation failure if the user supplied a large optlen
value. That is because some of them called memdup_user() without a ceiling
on optlen, allowing it to try to allocate really large buffers.

This patch adds a ceiling by limiting optlen to the maximum allowed that
would still make sense for these sockopt.

Reported-by: Hangbin Liu <haliu@redhat.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
---
 net/sctp/socket.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 54c046783a89e76c9909ee85c83e6be38ada41a7..022b94f11fd8ac0d3b839b16dfc14f86abf2324f 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -3498,6 +3498,8 @@ static int sctp_setsockopt_hmac_ident(struct sock *sk,
 
 	if (optlen < sizeof(struct sctp_hmacalgo))
 		return -EINVAL;
+	optlen = min_t(unsigned int, optlen, sizeof(struct sctp_hmacalgo) +
+					     SCTP_AUTH_NUM_HMACS * sizeof(u16));
 
 	hmacs = memdup_user(optval, optlen);
 	if (IS_ERR(hmacs))
@@ -3536,6 +3538,11 @@ static int sctp_setsockopt_auth_key(struct sock *sk,
 
 	if (optlen <= sizeof(struct sctp_authkey))
 		return -EINVAL;
+	/* authkey->sca_keylength is u16, so optlen can't be bigger than
+	 * this.
+	 */
+	optlen = min_t(unsigned int, optlen, USHRT_MAX +
+					     sizeof(struct sctp_authkey));
 
 	authkey = memdup_user(optval, optlen);
 	if (IS_ERR(authkey))
@@ -3893,6 +3900,9 @@ static int sctp_setsockopt_reset_streams(struct sock *sk,
 
 	if (optlen < sizeof(*params))
 		return -EINVAL;
+	/* srs_number_streams is u16, so optlen can't be bigger than this. */
+	optlen = min_t(unsigned int, optlen, USHRT_MAX +
+					     sizeof(__u16) * sizeof(*params));
 
 	params = memdup_user(optval, optlen);
 	if (IS_ERR(params))
-- 
2.14.3

[PATCH net 3/3] sctp: make use of pre-calculated len

[Marcelo Ricardo Leitner]

Some sockopt handling functions were calculating the length of the
buffer to be written to userspace and then calculating it again when
actually writing the buffer, which could lead to some write not using
an up-to-date length.

This patch updates such places to just make use of the len variable.

Also, replace some sizeof(type) to sizeof(var).

Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
---
 net/sctp/socket.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 022b94f11fd8ac0d3b839b16dfc14f86abf2324f..9b01e994f66108a12abc31f452482f1de8749d84 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -5025,7 +5025,7 @@ static int sctp_getsockopt_autoclose(struct sock *sk, int len, char __user *optv
 	len = sizeof(int);
 	if (put_user(len, optlen))
 		return -EFAULT;
-	if (copy_to_user(optval, &sctp_sk(sk)->autoclose, sizeof(int)))
+	if (copy_to_user(optval, &sctp_sk(sk)->autoclose, len))
 		return -EFAULT;
 	return 0;
 }
@@ -5655,6 +5655,9 @@ static int sctp_getsockopt_local_addrs(struct sock *sk, int len,
 		err = -EFAULT;
 		goto out;
 	}
+	/* XXX: We should have accounted for sizeof(struct sctp_getaddrs) too,
+	 * but we can't change it anymore.
+	 */
 	if (put_user(bytes_copied, optlen))
 		err = -EFAULT;
 out:
@@ -6091,7 +6094,7 @@ static int sctp_getsockopt_maxseg(struct sock *sk, int len,
 		params.assoc_id = 0;
 	} else if (len >= sizeof(struct sctp_assoc_value)) {
 		len = sizeof(struct sctp_assoc_value);
-		if (copy_from_user(&params, optval, sizeof(params)))
+		if (copy_from_user(&params, optval, len))
 			return -EFAULT;
 	} else
 		return -EINVAL;
@@ -6261,7 +6264,9 @@ static int sctp_getsockopt_active_key(struct sock *sk, int len,
 
 	if (len < sizeof(struct sctp_authkeyid))
 		return -EINVAL;
-	if (copy_from_user(&val, optval, sizeof(struct sctp_authkeyid)))
+
+	len = sizeof(struct sctp_authkeyid);
+	if (copy_from_user(&val, optval, len))
 		return -EFAULT;
 
 	asoc = sctp_id2assoc(sk, val.scact_assoc_id);
@@ -6273,7 +6278,6 @@ static int sctp_getsockopt_active_key(struct sock *sk, int len,
 	else
 		val.scact_keynumber = ep->active_key_id;
 
-	len = sizeof(struct sctp_authkeyid);
 	if (put_user(len, optlen))
 		return -EFAULT;
 	if (copy_to_user(optval, &val, len))
@@ -6299,7 +6303,7 @@ static int sctp_getsockopt_peer_auth_chunks(struct sock *sk, int len,
 	if (len < sizeof(struct sctp_authchunks))
 		return -EINVAL;
 
-	if (copy_from_user(&val, optval, sizeof(struct sctp_authchunks)))
+	if (copy_from_user(&val, optval, sizeof(val)))
 		return -EFAULT;
 
 	to = p->gauth_chunks;
@@ -6344,7 +6348,7 @@ static int sctp_getsockopt_local_auth_chunks(struct sock *sk, int len,
 	if (len < sizeof(struct sctp_authchunks))
 		return -EINVAL;
 
-	if (copy_from_user(&val, optval, sizeof(struct sctp_authchunks)))
+	if (copy_from_user(&val, optval, sizeof(val)))
 		return -EFAULT;
 
 	to = p->gauth_chunks;
-- 
2.14.3

Re: [PATCH net 0/3] Some sockopt optlen fixes

[Neil Horman]

On Mon, Jan 08, 2018 at 07:02:26PM -0200, Marcelo Ricardo Leitner wrote:
> Hangbin Liu reported that some SCTP sockopt are allowing the user to get
> the kernel to allocate really large buffers by not having a ceiling on
> optlen.
> 
> This patchset address this issue (in patch 2), replace an GFP_ATOMIC
> that isn't needed and avoid calculating the option size multiple times
> in some setsockopt.
> 
> Marcelo Ricardo Leitner (3):
>   sctp: GFP_ATOMIC is not needed in sctp_setsockopt_events
>   sctp: add a ceiling to optlen in some sockopts
>   sctp: make use of pre-calculated len
> 
>  net/sctp/socket.c | 28 +++++++++++++++++++++-------
>  1 file changed, 21 insertions(+), 7 deletions(-)
> 
> -- 
> 2.14.3
> 
> 
Series
Acked-by: Neil Horman <nhorman@tuxdriver.com>

Re: [PATCH net 0/3] Some sockopt optlen fixes

[David Miller]

From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Date: Mon,  8 Jan 2018 19:02:26 -0200

> Hangbin Liu reported that some SCTP sockopt are allowing the user to get
> the kernel to allocate really large buffers by not having a ceiling on
> optlen.
> 
> This patchset address this issue (in patch 2), replace an GFP_ATOMIC
> that isn't needed and avoid calculating the option size multiple times
> in some setsockopt.

Series applied, thank you.