Implement dumpability tracking and checks

We don't actually support core dumps, but some applications want to
get/set dumpability, which still has an effect in procfs.

Lack of support for set-uid binaries or fs creds simplifies things a
bit.

As-is, processes started via CreateProcess (i.e., init and sentryctl
exec) have normal dumpability. I'm a bit torn on whether sentryctl exec
tasks should be dumpable, but at least since they have no parent normal
UID/GID checks should protect them.

PiperOrigin-RevId: 251712714

1 files changed, 30 insertions, 0 deletions

diff --git a/pkg/sentry/mm/metadata.go b/pkg/sentry/mm/metadata.go
index 9768e51f1..c218006ee 100644
--- a/pkg/sentry/mm/metadata.go
+++ b/pkg/sentry/mm/metadata.go
@@ -20,6 +20,36 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 )
 
+// Dumpability describes if and how core dumps should be created.
+type Dumpability int
+
+const (
+	// NotDumpable indicates that core dumps should never be created.
+	NotDumpable Dumpability = iota
+
+	// UserDumpable indicates that core dumps should be created, owned by
+	// the current user.
+	UserDumpable
+
+	// RootDumpable indicates that core dumps should be created, owned by
+	// root.
+	RootDumpable
+)
+
+// Dumpability returns the dumpability.
+func (mm *MemoryManager) Dumpability() Dumpability {
+	mm.metadataMu.Lock()
+	defer mm.metadataMu.Unlock()
+	return mm.dumpability
+}
+
+// SetDumpability sets the dumpability.
+func (mm *MemoryManager) SetDumpability(d Dumpability) {
+	mm.metadataMu.Lock()
+	defer mm.metadataMu.Unlock()
+	mm.dumpability = d
+}
+
 // ArgvStart returns the start of the application argument vector.
 //
 // There is no guarantee that this value is sensible w.r.t. ArgvEnd.