From 58dc4452620ebefa75742661c538b8406b213b4a Mon Sep 17 00:00:00 2001 From: Than McIntosh Date: Tue, 15 Dec 2020 15:54:25 -0500 Subject: [release-branch.go1.15] cmd/internal/goobj2: fix buglet in object file reader The code in the Go object file reader was casting a pointer to mmaped memory into a large array prior to performing a read of the relocations section: return (*[1<<20]Reloc)(unsafe.Pointer(&r.b[off]))[:n:n] For very large object files, this artificial array isn't large enough (that is, there are more than 1048576 relocs to read), so update the code to use a larger artifical array size. Fixes #43214. Updates #41621. Change-Id: Ic047c8aef4f8a3839f2e7e3594bce652ebd6bd5b Reviewed-on: https://go-review.googlesource.com/c/go/+/278492 Run-TryBot: Than McIntosh TryBot-Result: Go Bot Reviewed-by: Cherry Zhang Reviewed-by: Jeremy Faller Trust: Than McIntosh (cherry picked from commit f4e7a6b905ce60448e506a3f6578d01b60602cdd) Reviewed-on: https://go-review.googlesource.com/c/go/+/278673 --- src/cmd/internal/goobj2/objfile.go | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/src/cmd/internal/goobj2/objfile.go b/src/cmd/internal/goobj2/objfile.go index 7f728e4f76..aba9b9856e 100644 --- a/src/cmd/internal/goobj2/objfile.go +++ b/src/cmd/internal/goobj2/objfile.go @@ -379,6 +379,11 @@ func (a *Aux) Write(w *Writer) { w.Bytes(a[:]) } // for testing func (a *Aux) fromBytes(b []byte) { copy(a[:], b) } +// Used to construct an artifically large array type when reading an +// item from the object file relocs section or aux sym section (needs +// to work on 32-bit as well as 64-bit). See issue 41621. +const huge = (1<<31 - 1) / RelocSize + // Referenced symbol name. // // Serialized format: @@ -652,7 +657,7 @@ func (r *Reader) Reloc(i int, j int) *Reloc { func (r *Reader) Relocs(i int) []Reloc { off := r.RelocOff(i, 0) n := r.NReloc(i) - return (*[1 << 20]Reloc)(unsafe.Pointer(&r.b[off]))[:n:n] + return (*[huge]Reloc)(unsafe.Pointer(&r.b[off]))[:n:n] } // NAux returns the number of aux symbols of the i-th symbol. @@ -678,7 +683,7 @@ func (r *Reader) Aux(i int, j int) *Aux { func (r *Reader) Auxs(i int) []Aux { off := r.AuxOff(i, 0) n := r.NAux(i) - return (*[1 << 20]Aux)(unsafe.Pointer(&r.b[off]))[:n:n] + return (*[huge]Aux)(unsafe.Pointer(&r.b[off]))[:n:n] } // DataOff returns the offset of the i-th symbol's data. -- cgit v1.2.3-54-g00ecf