Re: [merged mm-hotfixes-stable] mm-vmalloc-add-a-safer-version-of-find_vm_area-for-debug.patch removed from -mm tree

[Lorenzo Stoakes]

On Wed, 6 Sept 2023 at 16:09, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
>
> The quilt patch titled
>      Subject: mm/vmalloc: add a safer version of find_vm_area() for debug
> has been removed from the -mm tree.  Its filename was
>      mm-vmalloc-add-a-safer-version-of-find_vm_area-for-debug.patch
>
> This patch was dropped because it was merged into the mm-hotfixes-stable branch
> of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Hmm, I had outstanding review on this :/ I guess I will have to send a
follow up patch to address those concerns...


>
> ------------------------------------------------------
> From: "Joel Fernandes (Google)" <joel@xxxxxxxxxxxxxxxxx>
> Subject: mm/vmalloc: add a safer version of find_vm_area() for debug
> Date: Mon, 4 Sep 2023 18:08:04 +0000
>
> It is unsafe to dump vmalloc area information when trying to do so from
> some contexts.  Add a safer trylock version of the same function to do a
> best-effort VMA finding and use it from vmalloc_dump_obj().
>
> [applied test robot feedback on unused function fix.]
> [applied Uladzislau feedback on locking.]
> Link: https://lkml.kernel.org/r/20230904180806.1002832-1-joel@xxxxxxxxxxxxxxxxx
> Fixes: 98f180837a89 ("mm: Make mem_dump_obj() handle vmalloc() memory")
> Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
> Reviewed-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> Reported-by: Zhen Lei <thunder.leizhen@xxxxxxxxxxxxxxx>
> Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Cc: Zqiang <qiang.zhang1211@xxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
>
>  mm/vmalloc.c |   26 ++++++++++++++++++++++----
>  1 file changed, 22 insertions(+), 4 deletions(-)
>
> --- a/mm/vmalloc.c~mm-vmalloc-add-a-safer-version-of-find_vm_area-for-debug
> +++ a/mm/vmalloc.c
> @@ -4278,14 +4278,32 @@ void pcpu_free_vm_areas(struct vm_struct
>  #ifdef CONFIG_PRINTK
>  bool vmalloc_dump_obj(void *object)
>  {
> -       struct vm_struct *vm;
>         void *objp = (void *)PAGE_ALIGN((unsigned long)object);
> +       const void *caller;
> +       struct vm_struct *vm;
> +       struct vmap_area *va;
> +       unsigned long addr;
> +       unsigned int nr_pages;
> +
> +       if (!spin_trylock(&vmap_area_lock))
> +               return false;
> +       va = __find_vmap_area((unsigned long)objp, &vmap_area_root);
> +       if (!va) {
> +               spin_unlock(&vmap_area_lock);
> +               return false;
> +       }
>
> -       vm = find_vm_area(objp);
> -       if (!vm)
> +       vm = va->vm;
> +       if (!vm) {
> +               spin_unlock(&vmap_area_lock);
>                 return false;
> +       }
> +       addr = (unsigned long)vm->addr;
> +       caller = vm->caller;
> +       nr_pages = vm->nr_pages;
> +       spin_unlock(&vmap_area_lock);
>         pr_cont(" %u-page vmalloc region starting at %#lx allocated at %pS\n",
> -               vm->nr_pages, (unsigned long)vm->addr, vm->caller);
> +               nr_pages, addr, caller);
>         return true;
>  }
>  #endif
> _
>
> Patches currently in -mm which might be from joel@xxxxxxxxxxxxxxxxx are
>
>


--
Lorenzo Stoakes
https://ljs.io