Re: [PATCH -next v2] uprobes: fix two zero old_folio bugs in __replace_page()

[Tong Tiangen]

在 2025/2/22 10:37, Tong Tiangen 写道:
> 在 2025/2/21 23:28, Oleg Nesterov 写道:
> > On 02/21, Tong Tiangen wrote:
> > > --- a/kernel/events/uprobes.c
> > > +++ b/kernel/events/uprobes.c
> > > @@ -506,6 +506,11 @@ int uprobe_write_opcode(struct arch_uprobe 
> > > *auprobe, struct mm_struct *mm,
> > >       if (ret <= 0)
> > >           goto put_old;
> > >
> > > +    if (is_zero_page(old_page)) {
> > > +        ret = -EINVAL;
> > > +        goto put_old;
> > > +    }
> >
> > I agree with David, the subject looks a bit misleading.
> >
> > And. I won't insist, this is cosmetic, but if you send V2 please consider
> > moving the "verify_opcode()" check down, after the 
> > is_zero_page/PageCompound
> > checks.
> >
> > Oleg.
>
> OK, check the validity of the old page first and modify the subject in
> v3 .
>
> Thanks.

I'm going to add a new patch to moving the "verify_opcode()" check down
, IIUC that "!PageAnon(old_page)" below also needs to be moved together,
and as David said this can be triggered by user space, so delete the use
 of "WARN", as follows:


@@ -502,20 +502,16 @@ int uprobe_write_opcode(struct arch_uprobe 
*auprobe, struct mm_struct *mm,
        if (IS_ERR(old_page))
                return PTR_ERR(old_page);

-       ret = verify_opcode(old_page, vaddr, &opcode);
-       if (ret <= 0)
+       ret = -EINVAL;
+       if (is_zero_page(old_page))
                goto put_old;

-       if (is_zero_page(old_page)) {
-               ret = -EINVAL;
+       if (!is_register && (PageCompound(old_page) || !PageAnon(old_page)))
                goto put_old;
-       }

-       if (WARN(!is_register && PageCompound(old_page),
-                "uprobe unregister should never work on compound 
page\n")) {
-               ret = -EINVAL;
+       ret = verify_opcode(old_page, vaddr, &opcode);
+       if (ret <= 0)
                goto put_old;
-       }

        /* We are going to replace instruction, update ref_ctr. */
        if (!ref_ctr_updated && uprobe->ref_ctr_offset) {
@@ -526,10 +522,6 @@ int uprobe_write_opcode(struct arch_uprobe 
*auprobe, struct mm_struct *mm,
                ref_ctr_updated = 1;
        }

-       ret = 0;
-       if (!is_register && !PageAnon(old_page))
-               goto put_old;
-
        ret = anon_vma_prepare(vma);

Thanks.
> > .
>
> .