pkg/host: improve openat check

* Add support for non-obvious open commands

* Adding Michael Specter to CONTRIBUTORS

* update

* /pkg/host/host_linux.go: leverage .txt for OpenAt

Allows users to specify OpenAt flags. Currently, Syzkaller will
automatically attempt to open device nodes at startup, and ignore
descriptions that do not exist. Unfortunately, Syzkaller only opens with
read-only permissions, and some device drivers will
return -EINVAL or likewise if the correct flags are not specified.

1 files changed, 20 insertions, 6 deletions

diff --git a/pkg/host/host_linux.go b/pkg/host/host_linux.go
index 67ca37047..b4b83d188 100644
--- a/pkg/host/host_linux.go
+++ b/pkg/host/host_linux.go
@@ -312,18 +312,32 @@ func isSupportedSocket(c *prog.Syscall) (bool, string) {
 }
 
 func isSupportedOpenAt(c *prog.Syscall) (bool, string) {
+	var fd int
+	var err error
+
 	fname, ok := extractStringConst(c.Args[1])
 	if !ok || len(fname) == 0 || fname[0] != '/' {
 		return true, ""
 	}
-	fd, err := syscall.Open(fname, syscall.O_RDONLY, 0)
-	if fd != -1 {
-		syscall.Close(fd)
+
+	modes := []int{syscall.O_RDONLY, syscall.O_WRONLY, syscall.O_RDWR}
+
+	// Attempt to extract flags from the syscall description
+	if mode, ok := c.Args[2].(*prog.ConstType); ok {
+		modes = []int{int(mode.Val)}
 	}
-	if err != nil {
-		return false, fmt.Sprintf("open(%v) failed: %v", fname, err)
+
+	for _, mode := range modes {
+		fd, err = syscall.Open(fname, mode, 0)
+		if fd != -1 {
+			syscall.Close(fd)
+		}
+		if err == nil {
+			return true, ""
+		}
 	}
-	return true, ""
+
+	return false, fmt.Sprintf("open(%v) failed: %v", fname, err)
 }
 
 func isSupportedMount(c *prog.Syscall, sandbox string) (bool, string) {