runsc/cmd: fix unintended FD closing in gofer

nixprime · gvisor-bot · commit 87373a837f6d · 2025-10-23T14:07:33.000-07:00
PiperOrigin-RevId: 823179726
diff --git a/runsc/cmd/gofer.go b/runsc/cmd/gofer.go
@@ -193,7 +193,6 @@ func (g *Gofer) Execute(_ context.Context, f *flag.FlagSet, args ...any) subcomm
 			defer cleanupUnmounter()
 		}
 	}
-	goferToHostRPC.Close()
 	if g.applyCaps {
 		overrides := g.syncFDs.flags()
 		overrides["apply-caps"] = "false"
@@ -207,6 +206,11 @@ func (g *Gofer) Execute(_ context.Context, f *flag.FlagSet, args ...any) subcomm
 		panic("unreachable")
 	}
 
+	// This can't happen until after setCapsAndCallSelf(), since otherwise the
+	// re-executed gofer may reuse goferToHostRPCFD's file descriptor for an
+	// unrelated file.
+	goferToHostRPC.Close()
+
 	// Start profiling. This will be a noop if no profiling arguments were passed.
 	profileOpts := profile.MakeOpts(&g.profileFDs, conf.ProfileGCInterval)
 	g.stopProfiling = profile.Start(profileOpts)

Original file line number	Diff line number	Diff line change
`@@ -193,7 +193,6 @@ func (g Gofer) Execute(_ context.Context, f flag.FlagSet, args ...any) subcomm`
`193`	`193`	`defer cleanupUnmounter()`
`194`	`194`	`}`
`195`	`195`	`}`
`196`		`- goferToHostRPC.Close()`
`197`	`196`	`if g.applyCaps {`
`198`	`197`	`overrides := g.syncFDs.flags()`
`199`	`198`	`overrides["apply-caps"] = "false"`
`@@ -207,6 +206,11 @@ func (g Gofer) Execute(_ context.Context, f flag.FlagSet, args ...any) subcomm`
`207`	`206`	`panic("unreachable")`
`208`	`207`	`}`
`209`	`208`
	`209`	`+ // This can't happen until after setCapsAndCallSelf(), since otherwise the`
	`210`	`+ // re-executed gofer may reuse goferToHostRPCFD's file descriptor for an`
	`211`	`+ // unrelated file.`
	`212`	`+ goferToHostRPC.Close()`
	`213`	`+`
`210`	`214`	`// Start profiling. This will be a noop if no profiling arguments were passed.`
`211`	`215`	`profileOpts := profile.MakeOpts(&g.profileFDs, conf.ProfileGCInterval)`
`212`	`216`	`g.stopProfiling = profile.Start(profileOpts)`