From: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>
3.4.111-rc1 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@xxxxxxxxxxxxx>
Reviewed-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Reviewed-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
Acked-by: Santosh Shilimkar <santosh.shilimkar@xxxxxxxxxx>
Signed-off-by: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Zefan Li <lizefan@xxxxxxxxxx>
---
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 be3eecd..9e07c75 100644
--- a/net/rds/connection.c
+++ b/net/rds/connection.c
@@ -178,12 +178,6 @@ 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 88eace5..31c9fa4 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);
--
1.9.1
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