On Mon, Feb 24, 2025 at 10:24 PM Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> wrote: > > On Mon, Feb 24, 2025 at 10:52:45PM +0000, jeffxu@xxxxxxxxxxxx wrote: > > From: Jeff Xu <jeffxu@xxxxxxxxxxxx> > > > > Provide support to mseal the uprobe mapping. > > > > Unlike other system mappings, the uprobe mapping is not > > established during program startup. However, its lifetime is the same > > as the process's lifetime. It could be sealed from creation. > > > > I thought we agreed not to enable this for now? What testing > have you done to ensure this is functional? > I honestly don't know much about uprobe. I don't recall that I agree to ignore that though. As indicated in the cover letter, it is my understanding that uprobe's mapping's lifetime are the same as process's lifetime, thus sealable. [1] Oleg Nesterov, also cc, seems OK with mseal it in the early version of this patch [2] Are there any potential downsides of doing this? If yes, I can remove it. I'm also looking at Oleg to give more guidance on this :-), or if there are some functional tests that I need to do for uprobe. [1] https://lore.kernel.org/all/20241005200741.GA24353@xxxxxxxxxx/ [2] https://lore.kernel.org/all/20241005200741.GA24353@xxxxxxxxxx/ > I mean is this literally _all_ uprobe mappings now being sealed? > > I'd really like some more assurances on this one. And what are you > mitigating by sealing these? I get VDSO (kinda) but uprobes? > > You really need to provide more justification here. Sure. In our threat model, we need to seal all r-x, r--, and --x mappings to prevent them from becoming writable. This applies to all mappings, regardless of whether they're created by the kernel or dynamic linker. > > Signed-off-by: Jeff Xu <jeffxu@xxxxxxxxxxxx> > > --- > > kernel/events/uprobes.c | 5 ++++- > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > > index 2ca797cbe465..8dcdfa0d306b 100644 > > --- a/kernel/events/uprobes.c > > +++ b/kernel/events/uprobes.c > > @@ -1662,6 +1662,7 @@ static const struct vm_special_mapping xol_mapping = { > > static int xol_add_vma(struct mm_struct *mm, struct xol_area *area) > > { > > struct vm_area_struct *vma; > > + unsigned long vm_flags; > > int ret; > > > > if (mmap_write_lock_killable(mm)) > > @@ -1682,8 +1683,10 @@ static int xol_add_vma(struct mm_struct *mm, struct xol_area *area) > > } > > } > > > > + vm_flags = VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO; > > + vm_flags |= VM_SEALED_SYSMAP; > > vma = _install_special_mapping(mm, area->vaddr, PAGE_SIZE, > > - VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO, > > + vm_flags, > > &xol_mapping); > > if (IS_ERR(vma)) { > > ret = PTR_ERR(vma); > > -- > > 2.48.1.658.g4767266eb4-goog > >
