lkml.org 
[lkml]   [2015]   [Nov]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[Resend PATCH] RDS: fix race condition when sending a message on unbound socket
Date
From: Quentin Casasnovas <quentin.casasnovas@oracle.com>

Sasha's found a NULL pointer dereference in the RDS connection code when
sending a message to an apparently unbound socket. The problem is caused
by the code checking if the socket is bound in rds_sendmsg(), which checks
the rs_bound_addr field without taking a lock on the socket. This opens a
race where rs_bound_addr is temporarily set but where the transport is not
in rds_bind(), leading to a NULL pointer dereference when trying to
dereference 'trans' in __rds_conn_create().

Vegard wrote a reproducer for this issue, so kindly ask him to share if
you're interested.

I cannot reproduce the NULL pointer dereference using Vegard's reproducer
with this patch, whereas I could without.

Complete earlier incomplete fix to CVE-2015-6937:

74e98eb08588 ("RDS: verify the underlying transport exists before creating a connection")

Cc: David S. Miller <davem@davemloft.net>
Cc: stable@vger.kernel.org

Reviewed-by: Vegard Nossum <vegard.nossum@oracle.com>
Reviewed-by: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: Quentin Casasnovas <quentin.casasnovas@oracle.com>
---
Dave,

Resending refreshed version from earlier patch which was missed out
for some reason.
https://lkml.org/lkml/2015/10/16/530

It applies cleanly against linus master as well as net-next. I
have also pushed it on my tree below.
git://git.kernel.org/pub/scm/linux/kernel/git/ssantosh/linux.git 4.4/net-next/rds-fix


net/rds/connection.c | 6 ------
net/rds/send.c | 4 +++-
2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/net/rds/connection.c b/net/rds/connection.c
index d456403..e3b118c 100644
--- a/net/rds/connection.c
+++ b/net/rds/connection.c
@@ -186,12 +186,6 @@ static struct rds_connection *__rds_conn_create(struct net *net,
}
}

- if (trans == NULL) {
- kmem_cache_free(rds_conn_slab, conn);
- conn = ERR_PTR(-ENODEV);
- goto out;
- }
-
conn->c_trans = trans;

ret = trans->conn_alloc(conn, gfp);
diff --git a/net/rds/send.c b/net/rds/send.c
index 827155c..c9cdb35 100644
--- a/net/rds/send.c
+++ b/net/rds/send.c
@@ -1013,11 +1013,13 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
release_sock(sk);
}

- /* racing with another thread binding seems ok here */
+ lock_sock(sk);
if (daddr == 0 || rs->rs_bound_addr == 0) {
+ release_sock(sk);
ret = -ENOTCONN; /* XXX not a great errno */
goto out;
}
+ release_sock(sk);

if (payload_len > rds_sk_sndbuf(rs)) {
ret = -EMSGSIZE;
--
1.9.1


\
 
 \ /
  Last update: 2015-11-24 20:41    [W:0.051 / U:0.432 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site