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* Re: linux-4.4/net/sunrpc/auth_gss/gss_krb5_mech.c:296: Undefined Behaviour
       [not found] <DUB128-W91EBE8E198A948D174CCC9CCF0@phx.gbl>
@ 2016-01-21 19:34 ` bfields
  0 siblings, 0 replies; only message in thread
From: bfields @ 2016-01-21 19:34 UTC (permalink / raw)
  To: David Binderman; +Cc: jlayton@poochiereds.net, linux-nfs@vger.kernel.org

On Sun, Jan 17, 2016 at 08:31:54PM +0000, David Binderman wrote:
> [linux-4.4/net/sunrpc/auth_gss/gss_krb5_mech.c:296]: (warning) Invalid test for overflow 'p+20<p'. Condition is always false unless there is overflow, and overflow is Undefined Behaviour.
> 
> Source code is
> 
>    if (unlikely(p + 20> end || p + 20 < p)) {

Looks like we make that assumption all over; e.g. see the checks in
xdr_reserve_space and __xdr_inline_decode.  I guess that should be

	if (unlikely(end - p < 20))

?

What's the practical effect right now?  (E.g. does gcc actually violate
our assumption here currently?)

--b.

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2016-01-21 19:34 ` linux-4.4/net/sunrpc/auth_gss/gss_krb5_mech.c:296: Undefined Behaviour bfields

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