On Fri, 29 Apr 2022 12:25:11 +0200 Christian Schoenebeck <qemu_...@crudebyte.com> wrote:
> mknod() on macOS does not support creating sockets, so divert to > call sequence socket(), bind() and fchmodat() respectively if S_IFSOCK > was passed with mode argument. > > Link: https://lore.kernel.org/qemu-devel/17933734.zYzKuhC07K@silver/ > Signed-off-by: Christian Schoenebeck <qemu_...@crudebyte.com> > --- > hw/9pfs/9p-util-darwin.c | 42 +++++++++++++++++++++++++++++++++++++++- > 1 file changed, 41 insertions(+), 1 deletion(-) > > diff --git a/hw/9pfs/9p-util-darwin.c b/hw/9pfs/9p-util-darwin.c > index e24d09763a..619c403ba7 100644 > --- a/hw/9pfs/9p-util-darwin.c > +++ b/hw/9pfs/9p-util-darwin.c > @@ -74,6 +74,42 @@ int fsetxattrat_nofollow(int dirfd, const char *filename, > const char *name, > */ > #if defined CONFIG_PTHREAD_FCHDIR_NP > > +static int create_socket_file_at_cwd(const char *filename, mode_t mode) { > + int fd, err; > + struct sockaddr_un addr = { > + .sun_family = AF_UNIX > + }; > + > + err = snprintf(addr.sun_path, sizeof(addr.sun_path), "./%s", filename); > + if (err < 0 || err >= sizeof(addr.sun_path)) { According to POSIX [1]: The snprintf() function shall fail if: [EOVERFLOW] [CX] [Option Start] The value of n is greater than {INT_MAX}. [Option End] [1] https://pubs.opengroup.org/onlinepubs/9699919799/functions/snprintf.html Since we're passing sizeof(addr.sun_path), I'm pretty sure snprintf() cannot fail. No big deal. Reviewed-by: Greg Kurz <gr...@kaod.org> > + errno = ENAMETOOLONG; > + return -1; > + } > + fd = socket(PF_UNIX, SOCK_DGRAM, 0); > + if (fd == -1) { > + return fd; > + } > + err = bind(fd, (struct sockaddr *) &addr, sizeof(addr)); > + if (err == -1) { > + goto out; > + } > + /* > + * FIXME: Should rather be using descriptor-based fchmod() on the > + * socket file descriptor above (preferably before bind() call), > + * instead of path-based fchmodat(), to prevent concurrent transient > + * state issues between creating the named FIFO file at bind() and > + * delayed adjustment of permissions at fchmodat(). However currently > + * macOS (12.x) does not support such operations on socket file > + * descriptors yet. > + * > + * Filed report with Apple: FB9997731 > + */ > + err = fchmodat(AT_FDCWD, filename, mode, AT_SYMLINK_NOFOLLOW_ANY); > +out: > + close_preserve_errno(fd); > + return err; > +} > + > int qemu_mknodat(int dirfd, const char *filename, mode_t mode, dev_t dev) > { > int preserved_errno, err; > @@ -93,7 +129,11 @@ int qemu_mknodat(int dirfd, const char *filename, mode_t > mode, dev_t dev) > if (pthread_fchdir_np(dirfd) < 0) { > return -1; > } > - err = mknod(filename, mode, dev); > + if (S_ISSOCK(mode)) { > + err = create_socket_file_at_cwd(filename, mode); > + } else { > + err = mknod(filename, mode, dev); > + } > preserved_errno = errno; > /* Stop using the thread-local cwd */ > pthread_fchdir_np(-1);