Re: [PATCH] RDS: Fix rds-ping inducing kernel panic

[Leon Romanovsky]

On Mon, Jan 22, 2018 at 03:24:15AM -0800, Kees Cook wrote:
> As described in: https://bugzilla.redhat.com/show_bug.cgi?id=822754
>
> Attempting an RDS connection from the IP address of an IPoIB interface
> to itself causes a kernel panic due to a BUG_ON() being triggered.
> Making the test less strict allows rds-ping to work without crashing
> the machine.
>
> A local unprivileged user could use this flaw to crash the sytem.

s/sytem/system

>
> I think this fix was written by Jay Fenlason <fenlason@xxxxxxxxxx>,
> and extracted from the RedHat kernel patches here:
>
> https://oss.oracle.com/git/gitweb.cgi?p=redpatch.git;a=commitdiff;h=c7b6a0a1d8d636852be130fa15fa8be10d4704e8
>
> This fix appears to have been carried by at least RedHat, Oracle, and
> Ubuntu for several years.
>
> CVE-2012-2372
>
> Reported-by: Honggang Li <honli@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
> This is what I get for researching CVE lifetimes...
> ---
>  net/rds/ib_send.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/rds/ib_send.c b/net/rds/ib_send.c
> index 8557a1cae041..5fbf635d17cb 100644
> --- a/net/rds/ib_send.c
> +++ b/net/rds/ib_send.c
> @@ -506,7 +506,7 @@ int rds_ib_xmit(struct rds_connection *conn, struct rds_message *rm,
>  	int flow_controlled = 0;
>  	int nr_sig = 0;
>
> -	BUG_ON(off % RDS_FRAG_SIZE);
> +	BUG_ON(!conn->c_loopback && off % RDS_FRAG_SIZE);
>  	BUG_ON(hdr_off != 0 && hdr_off != sizeof(struct rds_header));

To be honest this function full of BUG_ONs and it looks fishy to have them there.
Why don't we return EINVAL instead of crashing system?

Thanks

>
>  	/* Do not send cong updates to IB loopback */
> --
> 2.7.4
>
>
> --
> Kees Cook
> Pixel Security

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