This is a note to let you know that I've just added the patch titled
RDS: fix race condition when sending a message on unbound socket
to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rds-fix-race-condition-when-sending-a-message-on-unbound-socket.patch
and it can be found in the queue-4.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Fri Dec 11 11:39:13 EST 2015
From: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>
Date: Tue, 24 Nov 2015 17:13:21 -0500
Subject: RDS: fix race condition when sending a message on unbound socket
From: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>
[ Upstream commit 8c7188b23474cca017b3ef354c4a58456f68303a ]
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>
Cc: stable@xxxxxxxxxxxxxxx
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: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/rds/connection.c | 6 ------
net/rds/send.c | 4 +++-
2 files changed, 3 insertions(+), 7 deletions(-)
--- a/net/rds/connection.c
+++ b/net/rds/connection.c
@@ -187,12 +187,6 @@ new_conn:
}
}
- 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);
--- a/net/rds/send.c
+++ b/net/rds/send.c
@@ -986,11 +986,13 @@ int rds_sendmsg(struct socket *sock, str
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);
Patches currently in stable-queue which might be from quentin.casasnovas@xxxxxxxxxx are
queue-4.1/rds-fix-race-condition-when-sending-a-message-on-unbound-socket.patch
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