From 591ff0e424e3b30eb143bce06618cb8656784b90 Mon Sep 17 00:00:00 2001
From: Nicolas Lacasse <nlacasse@google.com>
Date: Wed, 6 May 2020 10:28:50 -0700
Subject: Add maximum memory limit.

PiperOrigin-RevId: 310179277
---
 pkg/sentry/syscalls/linux/sys_sysinfo.go | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

(limited to 'pkg/sentry/syscalls/linux')

diff --git a/pkg/sentry/syscalls/linux/sys_sysinfo.go b/pkg/sentry/syscalls/linux/sys_sysinfo.go
index a65b560c8..297de052a 100644
--- a/pkg/sentry/syscalls/linux/sys_sysinfo.go
+++ b/pkg/sentry/syscalls/linux/sys_sysinfo.go
@@ -29,13 +29,18 @@ func Sysinfo(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 	mf.UpdateUsage()
 	_, totalUsage := usage.MemoryAccounting.Copy()
 	totalSize := usage.TotalMemory(mf.TotalSize(), totalUsage)
+	memFree := totalSize - totalUsage
+	if memFree > totalSize {
+		// Underflow.
+		memFree = 0
+	}
 
 	// Only a subset of the fields in sysinfo_t make sense to return.
 	si := linux.Sysinfo{
 		Procs:    uint16(len(t.PIDNamespace().Tasks())),
 		Uptime:   t.Kernel().MonotonicClock().Now().Seconds(),
 		TotalRAM: totalSize,
-		FreeRAM:  totalSize - totalUsage,
+		FreeRAM:  memFree,
 		Unit:     1,
 	}
 	_, err := t.CopyOut(addr, si)
-- 
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