Commit 56af94aa authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Kees Cook
Browse files

samples: user-trap: fix strict-aliasing warning 



I started getting warnings for this one file, though I can't see what changed
since it was originally introduced in commit fec7b669 ("samples: add an
example of seccomp user trap").

samples/seccomp/user-trap.c: In function 'send_fd':
samples/seccomp/user-trap.c:50:11: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
   50 |         *((int *)CMSG_DATA(cmsg)) = fd;
      |          ~^~~~~~~~~~~~~~~~~~~~~~~
samples/seccomp/user-trap.c: In function 'recv_fd':
samples/seccomp/user-trap.c:83:18: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
   83 |         return *((int *)CMSG_DATA(cmsg));
      |                 ~^~~~~~~~~~~~~~~~~~~~~~~

Using a temporary pointer variable avoids the warning.

Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20240212111737.917428-1-arnd@kernel.org


Acked-by: default avatarTycho Andersen <tandersen@netflix.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent 55e68669

samples/seccomp/user-trap.c

+6 −2
Original line number Diff line number Diff line
@@ -33,6 +33,7 @@ static int send_fd(int sock, int fd) 
{

	struct msghdr msg = {};

	struct cmsghdr *cmsg;

	int *fd_ptr;

	char buf[CMSG_SPACE(sizeof(int))] = {0}, c = 'c';

	struct iovec io = {

		.iov_base = &c,
@@ -47,7 +48,8 @@ static int send_fd(int sock, int fd) 
	cmsg->cmsg_level = SOL_SOCKET;

	cmsg->cmsg_type = SCM_RIGHTS;

	cmsg->cmsg_len = CMSG_LEN(sizeof(int));

	*((int *)CMSG_DATA(cmsg)) = fd;

	fd_ptr = (int *)CMSG_DATA(cmsg);

	*fd_ptr = fd;

	msg.msg_controllen = cmsg->cmsg_len;



	if (sendmsg(sock, &msg, 0) < 0) {
@@ -62,6 +64,7 @@ static int recv_fd(int sock) 
{

	struct msghdr msg = {};

	struct cmsghdr *cmsg;

	int *fd_ptr;

	char buf[CMSG_SPACE(sizeof(int))] = {0}, c = 'c';

	struct iovec io = {

		.iov_base = &c,
@@ -79,8 +82,9 @@ static int recv_fd(int sock) 
	}



	cmsg = CMSG_FIRSTHDR(&msg);

	fd_ptr = (int *)CMSG_DATA(cmsg);



	return *((int *)CMSG_DATA(cmsg));

	return *fd_ptr;

}



static int user_trap_syscall(int nr, unsigned int flags)