Re: [RFC PATCH RESEND v2 1/2] mm/memfd: Add support for F_SEAL_FUTURE_EXEC to memfd

On Tue, Jan 7, 2025 at 6:21 AM Jeff Xu jeffxu@chromium.org wrote:

Do you know which code checks for VM_MAYEXEC flag in the mprotect code path ? it isn't obvious to me, i.e. when I grep the VM_MAYEXEC inside mm path, it only shows one place in mprotect and that doesn't do the work.

~/mm/mm$ grep VM_MAYEXEC * mmap.c: mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC; mmap.c: vm_flags &= ~VM_MAYEXEC; mprotect.c: if (rier && (vma->vm_flags & VM_MAYEXEC)) nommu.c: vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC; nommu.c: vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;

The check happens here:

/* newflags >> 4 shift VM_MAY% in place of VM_% */ if ((newflags & ~(newflags >> 4)) & VM_ACCESS_FLAGS) { error = -EACCES; break; }

Alice