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Subject[PATCH 4.19 020/134] sctp: use memdup_user instead of vmemdup_user
Date
4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit ef82bcfa671b9a635bab5fa669005663d8b177c5 ]

In sctp_setsockopt_bindx()/__sctp_setsockopt_connectx(), it allocates
memory with addrs_size which is passed from userspace. We used flag
GFP_USER to put some more restrictions on it in Commit cacc06215271
("sctp: use GFP_USER for user-controlled kmalloc").

However, since Commit c981f254cc82 ("sctp: use vmemdup_user() rather
than badly open-coding memdup_user()"), vmemdup_user() has been used,
which doesn't check GFP_USER flag when goes to vmalloc_*(). So when
addrs_size is a huge value, it could exhaust memory and even trigger
oom killer.

This patch is to use memdup_user() instead, in which GFP_USER would
work to limit the memory allocation with a huge addrs_size.

Note we can't fix it by limiting 'addrs_size', as there's no demand
for it from RFC.

Reported-by: syzbot+ec1b7575afef85a0e5ca@syzkaller.appspotmail.com
Fixes: c981f254cc82 ("sctp: use vmemdup_user() rather than badly open-coding memdup_user()")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sctp/socket.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1017,7 +1017,7 @@ static int sctp_setsockopt_bindx(struct
if (unlikely(addrs_size <= 0))
return -EINVAL;

- kaddrs = vmemdup_user(addrs, addrs_size);
+ kaddrs = memdup_user(addrs, addrs_size);
if (unlikely(IS_ERR(kaddrs)))
return PTR_ERR(kaddrs);

@@ -1025,7 +1025,7 @@ static int sctp_setsockopt_bindx(struct
addr_buf = kaddrs;
while (walk_size < addrs_size) {
if (walk_size + sizeof(sa_family_t) > addrs_size) {
- kvfree(kaddrs);
+ kfree(kaddrs);
return -EINVAL;
}

@@ -1036,7 +1036,7 @@ static int sctp_setsockopt_bindx(struct
* causes the address buffer to overflow return EINVAL.
*/
if (!af || (walk_size + af->sockaddr_len) > addrs_size) {
- kvfree(kaddrs);
+ kfree(kaddrs);
return -EINVAL;
}
addrcnt++;
@@ -1072,7 +1072,7 @@ static int sctp_setsockopt_bindx(struct
}

out:
- kvfree(kaddrs);
+ kfree(kaddrs);

return err;
}
@@ -1347,7 +1347,7 @@ static int __sctp_setsockopt_connectx(st
if (unlikely(addrs_size <= 0))
return -EINVAL;

- kaddrs = vmemdup_user(addrs, addrs_size);
+ kaddrs = memdup_user(addrs, addrs_size);
if (unlikely(IS_ERR(kaddrs)))
return PTR_ERR(kaddrs);

@@ -1367,7 +1367,7 @@ static int __sctp_setsockopt_connectx(st
err = __sctp_connect(sk, kaddrs, addrs_size, flags, assoc_id);

out_free:
- kvfree(kaddrs);
+ kfree(kaddrs);

return err;
}

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