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

[Joel Fernandes]

> On Sep 6, 2023, at 3:14 PM, Lorenzo Stoakes <lstoakes@xxxxxxxxx> wrote:
> 
> 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...

That works me because we also had some disagreements on some of the suggestions!

Looking forward to your patch and discussing it!

Cheers,

 - Joel


> 
> 
>> 
>> ------------------------------------------------------
>> 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