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Alberto Donizetti 0b25e97d03 [release-branch.go1.9] 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/88322
Run-TryBot: Andrew Bonventre <andybons@golang.org>
2018-01-22 20:25:04 +00:00
.github .github: add .md extension to SUPPORT file 2017-07-30 21:46:28 +00:00
api doc, api: add syscall.SysProcAttr.AmbientCaps change to 1.9 notes, API 2017-06-29 03:29:46 +00:00
doc doc: hide content blocked by GFW when served in CN 2018-01-20 05:07:43 +00:00
lib/time time: vendor tzdata-2017b and update test 2017-06-07 21:23:58 +00:00
misc [release-branch.go1.9] cmd/cgo: support large unsigned macro again 2017-10-25 20:23:52 +00:00
src [release-branch.go1.9] math/big: protect against aliasing in nat.divLarge 2018-01-22 20:25:04 +00:00
test [release-branch.go1.9] cmd/compile: fix runtime.KeepAlive 2018-01-22 20:25:01 +00:00
.gitattributes
.gitignore .gitignore: change path to zbootstrap.go 2017-04-19 02:13:58 +00:00
AUTHORS A+C: final updates for Go 1.9 2017-07-18 01:47:54 +00:00
CONTRIBUTING.md .github: recommend 'go bug' when filing an issue 2017-07-24 17:18:34 +00:00
CONTRIBUTORS A+C: final updates for Go 1.9 2017-07-18 01:47:54 +00:00
LICENSE
PATENTS
README.md readme: add attribution for the Gopher image 2017-02-03 19:39:41 +00:00
VERSION [release-branch.go1.9] go1.9.2 2017-10-25 20:24:05 +00:00
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