Messages in this thread Patch in this message | | | From | Jiri Slaby <> | Subject | [PATCH 3.12 83/91] RDS: fix race condition when sending a message on unbound socket | Date | Tue, 5 Jan 2016 18:47:07 +0100 |
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From: Quentin Casasnovas <quentin.casasnovas@oracle.com>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
commit 8c7188b23474cca017b3ef354c4a58456f68303a upstream.
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>
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> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Jiri Slaby <jslaby@suse.cz> --- 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 e88bf3976e54..642ad42c416b 100644 --- a/net/rds/connection.c +++ b/net/rds/connection.c @@ -177,12 +177,6 @@ static struct rds_connection *__rds_conn_create(__be32 laddr, __be32 faddr, } } - 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 88eace57dd6b..31c9fa464b11 100644 --- a/net/rds/send.c +++ b/net/rds/send.c @@ -955,11 +955,13 @@ int rds_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg, 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); /* size of rm including all sgs */ ret = rds_rm_size(msg, payload_len); -- 2.6.4
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