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Austin Clements 627798db4e reflect: fix out-of-bounds pointers calling no-result method
reflect.callReflect heap-allocates a stack frame and then constructs
pointers to the arguments and result areas of that frame. However, if
there are no results, the results pointer will point past the end of
the frame allocation. If there are also no arguments, the arguments
pointer will also point past the end of the frame allocation. If the
GC observes either these pointers, it may panic.

Fix this by not constructing these pointers if these areas of the
frame are empty.

This adds a test of calling no-argument/no-result methods via reflect,
since nothing in std did this before. However, it's quite difficult to
demonstrate the actual failure because it depends on both exact
allocation patterns and on GC scanning the goroutine's stack while
inside one of the typedmemmovepartial calls.

I also audited other uses of typedmemmovepartial and
memclrNoHeapPointers in reflect, since these are the most susceptible
to this. These appear to be the only two cases that can construct
out-of-bounds arguments to these functions.

Fixes #19724.

Change-Id: I4b83c596b5625dc4ad0567b1e281bad4faef972b
Reviewed-on: https://go-review.googlesource.com/38736
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
2017-03-29 15:28:49 +00:00
.github doc: improve issue template and contribution guidelines 2017-02-11 20:42:06 +00:00
api math/big: define Word as uint instead of uintptr 2017-02-21 19:31:40 +00:00
doc spec: for non-constant map keys, add reference to evaluation order section 2017-03-24 18:51:10 +00:00
lib/time *.bash: always use the same string equality operator 2017-03-14 21:46:31 +00:00
misc *.bash: always use the same string equality operator 2017-03-14 21:46:31 +00:00
src reflect: fix out-of-bounds pointers calling no-result method 2017-03-29 15:28:49 +00:00
test test: add test for gccgo compiler crash 2017-03-28 20:05:34 +00:00
.gitattributes
.gitignore cmd/dist: move cmd/go z files to cmd/go/internal/cfg 2017-02-03 20:30:52 +00:00
AUTHORS A+C: automated update 2016-12-21 03:22:22 +00:00
CONTRIBUTING.md doc: improve issue template and contribution guidelines 2017-02-11 20:42:06 +00:00
CONTRIBUTORS A+C: automated update 2016-12-21 03:22:22 +00:00
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README.md readme: add attribution for the Gopher image 2017-02-03 19:39:41 +00:00
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