commit | a5a3be16366579f6701642f41f9146ce196cd617 | [log] [tgz] |
---|---|---|
author | Alberto Donizetti <alb.donizetti@gmail.com> | Tue Nov 21 14:16:04 2017 +0100 |
committer | Andrew Bonventre <andybons@golang.org> | Tue Jan 23 03:27:42 2018 +0000 |
tree | 3c0621240b8600302afbf7d29eb7614147c3383f | |
parent | 45a42c9be5d7f1a31d642ae7618ba9bef120ecc8 [diff] |
[release-branch.go1.8] math/big: protect against aliasing in nat.divLarge In nat.divLarge (having signature (z nat).divLarge(u, uIn, v nat)), we check whether z aliases uIn or v, but aliasing is currently not checked for the u parameter. Unfortunately, z and u aliasing each other can in some cases cause errors in the computation. The q return parameter (which will hold the result's quotient), is unconditionally initialized as q = z.make(m + 1) When cap(z) ≥ m+1, z.make() will reuse z's backing array, causing q and z to share the same backing array. If then z aliases u, setting q during the quotient computation will then corrupt u, which at that point already holds computation state. To fix this, we add an alias(z, u) check at the beginning of the function, taking care of aliasing the same way we already do for uIn and v. Fixes #22830 Change-Id: I3ab81120d5af6db7772a062bb1dfc011de91f7ad Reviewed-on: https://go-review.googlesource.com/78995 Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com> Run-TryBot: Robert Griesemer <gri@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org> Reviewed-on: https://go-review.googlesource.com/89156 Run-TryBot: Andrew Bonventre <andybons@golang.org> Reviewed-by: Andrew Bonventre <andybons@golang.org>
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