syscall: return early on error in Recvmsg

Currently, Recvmsg may access the rsa buffer even if the underlying syscall
returns an error.

Following the same change done for x/sys/unix.Recvmsg in CL 734740.

For golang/go#76848

Change-Id: I2a145d822442a2033a76f4717317a39010b17bd5
Reviewed-on: https://go-review.googlesource.com/c/go/+/735121
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Florian Lehner <lehner.florian86@gmail.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>

diff --git a/src/syscall/syscall_unix.go b/src/syscall/syscall_unix.go
index d957b77dc41f7640bbd8bfe7f06a863587c4f1f2..60173f6d16305124eb3227b9b928f656236d67d1 100644 (file)
--- a/src/syscall/syscall_unix.go
+++ b/src/syscall/syscall_unix.go
@@ -385,6 +385,9 @@ func recvmsgInet6(fd int, p, oob []byte, flags int, from *SockaddrInet6) (n, oob
 func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn int, recvflags int, from Sockaddr, err error) {
        var rsa RawSockaddrAny
        n, oobn, recvflags, err = recvmsgRaw(fd, p, oob, flags, &rsa)
+       if err != nil {
+               return
+       }
        // source address is only specified if the socket is unconnected
        if rsa.Addr.Family != AF_UNSPEC {
                from, err = anyToSockaddr(&rsa)