git: 3a99aac66f8d - main - linux(4): Check the socket before any others sanity checks

The branch main has been updated by dchagin:

URL: https://cgit.FreeBSD.org/src/commit/?id=3a99aac66f8d12386e8382aaf29d2e82e6b5353b

commit 3a99aac66f8d12386e8382aaf29d2e82e6b5353b
Author:     Dmitry Chagin <dchagin@FreeBSD.org>
AuthorDate: 2022-05-28 20:29:12 +0000
Commit:     Dmitry Chagin <dchagin@FreeBSD.org>
CommitDate: 2022-05-28 20:29:12 +0000

    linux(4): Check the socket before any others sanity checks
    
    Strictly speaking, this check is performed by the kern_recvit(), but in
    the Linux emulation layer before calling the kernel we do other sanity
    checks and conversions from Linux types to the native types. This changes
    an order of the error returning that is critical for some buggy Linux
    applications.
    
    For recvmmsg() syscall this fixes a panic in case when the user-supplied
    vlen value is 0, then error is not initialized and garbage passed to the
    bsd_to_linux_errno().
    
    MFC after:              2 weeks
---
 sys/compat/linux/linux_socket.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/sys/compat/linux/linux_socket.c b/sys/compat/linux/linux_socket.c
index b5ec32835981..8aa425bc14c0 100644
--- a/sys/compat/linux/linux_socket.c
+++ b/sys/compat/linux/linux_socket.c
@@ -1731,7 +1731,14 @@ int
 linux_recvmsg(struct thread *td, struct linux_recvmsg_args *args)
 {
 	struct msghdr bsd_msg;
+	struct file *fp;
+	int error;
 
+	error = getsock_cap(td, args->s, &cap_recv_rights,
+	    &fp, NULL, NULL);
+	if (error != 0)
+		return (error);
+	fdrop(fp, td);
 	return (linux_recvmsg_common(td, args->s, PTRIN(args->msg),
 	    args->flags, &bsd_msg));
 }
@@ -1742,9 +1749,14 @@ linux_recvmmsg_common(struct thread *td, l_int s, struct l_mmsghdr *msg,
 {
 	struct msghdr bsd_msg;
 	struct timespec ts;
+	struct file *fp;
 	l_uint retval;
 	int error, datagrams;
 
+	error = getsock_cap(td, s, &cap_recv_rights,
+	    &fp, NULL, NULL);
+	if (error != 0)
+		return (error);
 	datagrams = 0;
 	while (datagrams < vlen) {
 		error = linux_recvmsg_common(td, s, &msg->msg_hdr,
@@ -1780,6 +1792,7 @@ linux_recvmmsg_common(struct thread *td, l_int s, struct l_mmsghdr *msg,
 	}
 	if (error == 0)
 		td->td_retval[0] = datagrams;
+	fdrop(fp, td);
 	return (error);
 }