Re: [PATCH] RDS: fix race condition when sending a message on unbound socket.

From: santosh shilimkar
Date: Tue Nov 03 2015 - 11:27:43 EST


On 11/3/2015 3:25 AM, Quentin Casasnovas wrote:
On Fri, Oct 16, 2015 at 10:47:49AM -0700, santosh shilimkar wrote:
On 10/16/2015 8:11 AM, Quentin Casasnovas wrote:
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")


For reference, this has been assigned CVE-2015-7990 on the oss-sec thread:

http://seclists.org/oss-sec/2015/q4/179

New CVE number than the older one. Thanks for the note.

Regards,
Santosh
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