On Thu, Aug 31, 2023 at 10:36:46PM +0200, Michal Clapinski wrote: > Add a way to check if an fd points to the memfd's original open fd > (the one created by memfd_create). > Useful because only the original open fd can be both writable and > executable. > > Signed-off-by: Michal Clapinski <mclapinski@xxxxxxxxxx> > --- > fs/fcntl.c | 3 +++ > include/uapi/linux/fcntl.h | 9 +++++++++ > 2 files changed, 12 insertions(+) > > diff --git a/fs/fcntl.c b/fs/fcntl.c > index e871009f6c88..301527e07a4d 100644 > --- a/fs/fcntl.c > +++ b/fs/fcntl.c > @@ -419,6 +419,9 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg, > case F_SET_RW_HINT: > err = fcntl_rw_hint(filp, cmd, arg); > break; > + case F_CHECK_ORIGINAL_MEMFD: > + err = !(filp->f_mode & FMODE_WRITER); > + break; Honestly, make this an ioctl on memfds. This is so specific that it really doesn't belong into fcntl().
