From: Daniel Borkmann Date: Fri, 4 Apr 2014 23:04:03 +0000 (+0200) Subject: net: filter: be more defensive on div/mod by X==0 X-Git-Tag: v3.15-rc1~47^2~9 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5f9fde5f799df7156eeb3fa58282e9fd2f38a5f8;p=pandora-kernel.git net: filter: be more defensive on div/mod by X==0 The old interpreter behaviour was that we returned with 0 whenever we found a division by 0 would take place. In the new interpreter we would currently just skip that instead and continue execution. It's true that a value of 0 as return might not be appropriate in all cases, but current users (socket filters -> drop packet, seccomp -> SECCOMP_RET_KILL, cls_bpf -> unclassified, etc) seem fine with that behaviour. Better this than undefined BPF program behaviour as it's expected that A contains the result of the division. In future, as more use cases open up, we could further adapt this return value to our needs, if necessary. So reintroduce return of 0 for division by 0 as in the old interpreter. Also in case of K which is guaranteed to be 32bit wide, sk_chk_filter() already takes care of preventing division by 0 invoked through K, so we can generally spare us these tests. Signed-off-by: Daniel Borkmann Reviewed-by: Alexei Starovoitov Signed-off-by: David S. Miller --- Reading git-diff-tree failed