From 0bf9410119613ac80a3b06503713e9859c2564b1 Mon Sep 17 00:00:00 2001 From: Austin Clements Date: Sat, 3 Oct 2020 16:44:22 -0400 Subject: [release-branch.go1.14] runtime: correct signature of call16 The signature of call16 is currently missing the "typ" parameter. This CL fixes this. This wasn't caught by vet because call16 is defined by macro expansion (see #17544), and we didn't notice the mismatch with the other call* functions because call16 is defined only on 32-bit architectures and lives alone in stubs32.go. Unfortunately, this means its GC signature is also wrong: the "arg" parameter is treated as a scalar rather than a pointer, so GC won't trace it and stack copying won't adjust it. This turns out to matter in exactly one case right now: on 32-bit architectures (which are the only architectures where call16 is defined), a stack-allocated defer of a function with a 16-byte or smaller argument frame including a non-empty result area can corrupt memory if the deferred function grows the stack and is invoked during a panic. Whew. All other current uses of reflectcall pass a heap-allocated "arg" frame (which happens to be reachable from other stack roots, so tracing isn't a problem). Curiously, in 2016, the signatures of all call* functions were wrong in exactly this way. CL 31654 fixed all of them in stubs.go, but missed the one in stubs32.go. Updates #41795. Fixes #41796. Change-Id: I31e3c0df201f79ee5707eeb8dc4ff0d13fc10ada Reviewed-on: https://go-review.googlesource.com/c/go/+/259338 Trust: Austin Clements Run-TryBot: Austin Clements TryBot-Result: Go Bot Reviewed-by: Cherry Zhang Reviewed-on: https://go-review.googlesource.com/c/go/+/259597 --- src/runtime/stubs32.go | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/runtime/stubs32.go b/src/runtime/stubs32.go index a7f52f6b9e..c4715fe989 100644 --- a/src/runtime/stubs32.go +++ b/src/runtime/stubs32.go @@ -11,4 +11,4 @@ import "unsafe" // Declarations for runtime services implemented in C or assembly that // are only present on 32 bit systems. -func call16(fn, arg unsafe.Pointer, n, retoffset uint32) +func call16(typ, fn, arg unsafe.Pointer, n, retoffset uint32) -- cgit v1.2.3-54-g00ecf