netdev - Re: [PATCH net-next v2 1/2] bpf: make htab inlining more robust wrt assumptions

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Message-ID: <b005c1b5-12c9-3477-b4e9-49798ac0e0ba@fb.com>
Date:   Fri, 18 Aug 2017 18:20:24 -0700
From:   Alexei Starovoitov <ast@...com>
To:     Daniel Borkmann <daniel@...earbox.net>, <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v2 1/2] bpf: make htab inlining more robust wrt
 assumptions

On 8/18/17 6:12 PM, Daniel Borkmann wrote:
> Commit 9015d2f59535 ("bpf: inline htab_map_lookup_elem()") was
> making the assumption that a direct call emission to the function
> __htab_map_lookup_elem() will always work out for JITs.
>
> This is currently true since all JITs we have are for 64 bit archs,
> but in case of 32 bit JITs like upcoming arm32, we get a NULL pointer
> dereference when executing the call to __htab_map_lookup_elem()
> since passed arguments are of a different size (due to pointer args)
> than what we do out of BPF. Guard and thus limit this for now for
> the current 64 bit JITs only.
>
> Reported-by: Shubham Bansal <illusionist.neo@...il.com>
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>

Acked-by: Alexei Starovoitov <ast@...nel.org>
Thanks. That's good robustness fix.