[PATCH] net: filter: make JITs zero A for SKF_AD_ALU_XOR_X

[David Miller]

From: Rabin Vincent <rabin at rab.in>
Date: Tue,  5 Jan 2016 16:23:07 +0100

> The SKF_AD_ALU_XOR_X ancillary is not like the other ancillary data
> instructions since it XORs A with X while all the others replace A with
> some loaded value.  All the BPF JITs fail to clear A if this is used as
> the first instruction in a filter.  This was found using american fuzzy
> lop.
> 
> Add a helper to determine if A needs to be cleared given the first
> instruction in a filter, and use this in the JITs.  Except for ARM, the
> rest have only been compile-tested.
> 
> Fixes: 3480593131e0 ("net: filter: get rid of BPF_S_* enum")
> Signed-off-by: Rabin Vincent <rabin at rab.in>

Applied and queued up for -stable, thanks!