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

[David Miller]

From: Santosh Shilimkar <santosh.shilimkar@xxxxxxxxxx>
Date: Tue, 24 Nov 2015 17:13:21 -0500

> From: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>
> 
> 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>

Applied and queued up for -stable, thanks.
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