From: Than McIntosh <thanm@google.com>
Date: Thu, 23 Apr 2020 12:43:29 +0000 (-0400)
Subject: [dev.link] cmd/link/internal/loader: fix buglet in section handling
X-Git-Tag: go1.15beta1~270^2^2~41
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=adea6a90e361629d20a68400c0c5cdcdfcdf087e;p=gostls13.git

[dev.link] cmd/link/internal/loader: fix buglet in section handling

Allow for the possibility that a client could call newExtSym(), then
ask for the section of the new sym before SetSectSym is called on it
(check in SymSect for this case).

Change-Id: I7bd78e7b3b7618943705b616f62ea78c4a1b68d0
Reviewed-on: https://go-review.googlesource.com/c/go/+/229603
Reviewed-by: Jeremy Faller <jeremy@golang.org>
---

diff --git a/src/cmd/link/internal/loader/loader.go b/src/cmd/link/internal/loader/loader.go
index 987feeb284..ba0cff3ff6 100644
--- a/src/cmd/link/internal/loader/loader.go
+++ b/src/cmd/link/internal/loader/loader.go
@@ -1075,6 +1075,12 @@ func (l *Loader) SetSymAlign(i Sym, align int32) {
 
 // SymValue returns the section of the i-th symbol. i is global index.
 func (l *Loader) SymSect(i Sym) *sym.Section {
+	if int(i) >= len(l.symSects) {
+		// symSects is extended lazily -- it the sym in question is
+		// outside the range of the existing slice, then we assume its
+		// section has not yet been set.
+		return nil
+	}
 	return l.sects[l.symSects[i]]
 }