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

[santosh shilimkar]

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")
>
> Signed-off-by: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>
> Reviewed-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
> Reviewed-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
> Cc: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
> Cc: Sasha Levin <sasha.levin@xxxxxxxxxx>
> Cc: Chien Yen <chien.yen@xxxxxxxxxx>
> Cc: Santosh Shilimkar <santosh.shilimkar@xxxxxxxxxx>
> Cc: David S. Miller <davem@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
Looks right. Am glad that we got deference issue as well as
the bind race fixed with it. Mail sent to Vegard for his test
case which I would like to add to my tests. Thanks for the fix.

FWIW,
Acked-by: Santosh Shilimkar <santosh.shilimkar@xxxxxxxxxx>

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