Re: kern/57622: memfd mmap does not work for requests < page size

["Robert Bagdan via gnats" <gnats-admin%NetBSD.org@localhost>]

The following reply was made to PR kern/57622; it has been noted by GNATS.

From: Robert Bagdan <kikadf.01%gmail.com@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/57622: memfd mmap does not work for requests < page size
Date: Sun, 22 Feb 2026 15:17:52 +0100

 I encountered the same mmap() EINVAL error with Wayland cursor loading
 on NetBSD 11.0_BETA/amd64.
 
 In this case the requested size is 2304 (derived from the cursor size:
 24 =C3=97 24 =C3=97 4).
 The sequence is:
 1) fd =3D memfd_create("wayland-cursor", MFD_CLOEXEC | MFD_ALLOW_SEALING
 | MFD_NOEXEC_SEAL)
 2) ftruncate(fd, size)
 3) mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED,  pool->fd, 0)
 
 The mmap() call memfd_mmap(), where:
 
 KASSERT(*offp =3D=3D round_page(*offp));
 KASSERT(size =3D=3D round_page(size));
 
 and the following check then fails:
 
 if (*offp + size > mfd->mfd_size)  {
 error =3D EINVAL;
 goto leave;
 }
 
 where mfd_size is still 2304, while size is already rounded up to 4096.
 
 --=20
 Regards,
 kikadf