On Sep 6, 2023, at 3:14 PM, Lorenzo Stoakes lstoakes@gmail.com wrote:

On Wed, 6 Sept 2023 at 16:09, Andrew Morton akpm@linux-foundation.org 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

...

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From: "Joel Fernandes (Google)" joel@joelfernandes.org 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@joelfernandes.org Fixes: 98f180837a89 ("mm: Make mem_dump_obj() handle vmalloc() memory") Signed-off-by: Joel Fernandes (Google) joel@joelfernandes.org Reviewed-by: Uladzislau Rezki (Sony) urezki@gmail.com Reported-by: Zhen Lei thunder.leizhen@huaweicloud.com Cc: Paul E. McKenney paulmck@kernel.org Cc: Zqiang qiang.zhang1211@gmail.com Cc: stable@vger.kernel.org Cc: Matthew Wilcox (Oracle) willy@infradead.org Signed-off-by: Andrew Morton akpm@linux-foundation.org

---

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@joelfernandes.org are

-- Lorenzo Stoakes https://ljs.io