From 331614c4daa5504ddfe35a96371cc34783d14cf1 Mon Sep 17 00:00:00 2001 From: Paschalis Tsilias Date: Fri, 18 Sep 2020 19:15:41 +0300 Subject: [PATCH] runtime: improve error messages after allocating a stack that is too big In the current implementation, we can observe crashes after calling debug.SetMaxStack and allocating a stack larger than 4GB since stackalloc works with 32-bit sizes. To avoid this, we define an upper limit as the largest feasible point we can grow a stack to and provide a better error message when we get a stack overflow. Fixes #41228 Change-Id: I55fb0a824f47ed9fb1fcc2445a4dfd57da9ef8d4 Reviewed-on: https://go-review.googlesource.com/c/go/+/255997 Run-TryBot: Keith Randall TryBot-Result: Go Bot Trust: Giovanni Bajo Reviewed-by: Keith Randall --- src/runtime/debug/garbage.go | 2 ++ src/runtime/proc.go | 5 +++++ src/runtime/stack.go | 10 ++++++++-- 3 files changed, 15 insertions(+), 2 deletions(-) diff --git a/src/runtime/debug/garbage.go b/src/runtime/debug/garbage.go index e36e54f12d..00f92c3ddf 100644 --- a/src/runtime/debug/garbage.go +++ b/src/runtime/debug/garbage.go @@ -106,6 +106,8 @@ func FreeOSMemory() { // the program crashes. // SetMaxStack returns the previous setting. // The initial setting is 1 GB on 64-bit systems, 250 MB on 32-bit systems. +// There may be a system-imposed maximum stack limit regardless +// of the value provided to SetMaxStack. // // SetMaxStack is useful mainly for limiting the damage done by // goroutines that enter an infinite recursion. It only limits future diff --git a/src/runtime/proc.go b/src/runtime/proc.go index 739745aa26..f4665220ae 100644 --- a/src/runtime/proc.go +++ b/src/runtime/proc.go @@ -128,6 +128,11 @@ func main() { maxstacksize = 250000000 } + // An upper limit for max stack size. Used to avoid random crashes + // after calling SetMaxStack and trying to allocate a stack that is too big, + // since stackalloc works with 32-bit sizes. + maxstackceiling = 2 * maxstacksize + // Allow newproc to start new Ms. mainStarted = true diff --git a/src/runtime/stack.go b/src/runtime/stack.go index 821c2e8436..613126c708 100644 --- a/src/runtime/stack.go +++ b/src/runtime/stack.go @@ -497,6 +497,8 @@ func stackfree(stk stack) { var maxstacksize uintptr = 1 << 20 // enough until runtime.main sets it for real +var maxstackceiling = maxstacksize + var ptrnames = []string{ 0: "scalar", 1: "ptr", @@ -1050,8 +1052,12 @@ func newstack() { } } - if newsize > maxstacksize { - print("runtime: goroutine stack exceeds ", maxstacksize, "-byte limit\n") + if newsize > maxstacksize || newsize > maxstackceiling { + if maxstacksize < maxstackceiling { + print("runtime: goroutine stack exceeds ", maxstacksize, "-byte limit\n") + } else { + print("runtime: goroutine stack exceeds ", maxstackceiling, "-byte limit\n") + } print("runtime: sp=", hex(sp), " stack=[", hex(gp.stack.lo), ", ", hex(gp.stack.hi), "]\n") throw("stack overflow") } -- 2.50.0