Re: [PATCH 2/2] mm: vmalloc: Pass proper vm_start into debugobjects

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On 4/17/2018 8:39 AM, Anshuman Khandual wrote:
On 04/16/2018 05:39 PM, Chintan Pandya wrote:


On 4/13/2018 5:31 PM, Anshuman Khandual wrote:
On 04/13/2018 05:03 PM, Chintan Pandya wrote:
Client can call vunmap with some intermediate 'addr'
which may not be the start of the VM area. Entire
unmap code works with vm->vm_start which is proper
but debug object API is called with 'addr'. This
could be a problem within debug objects.

Pass proper start address into debug object API.

Signed-off-by: Chintan Pandya <cpandya@xxxxxxxxxxxxxx>
---
   mm/vmalloc.c | 4 ++--
   1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 9ff21a1..28034c55 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1526,8 +1526,8 @@ static void __vunmap(const void *addr, int
deallocate_pages)
           return;
       }
   -    debug_check_no_locks_freed(addr, get_vm_area_size(area));
-    debug_check_no_obj_freed(addr, get_vm_area_size(area));
+    debug_check_no_locks_freed(area->addr, get_vm_area_size(area));
+    debug_check_no_obj_freed(area->addr, get_vm_area_size(area));

This kind of makes sense to me but I am not sure. We also have another
instance of this inside the function vm_unmap_ram() where we call for
Right, I missed it. I plan to add below stub in v2.

--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1124,15 +1124,15 @@ void vm_unmap_ram(const void *mem, unsigned int
count)
         BUG_ON(addr > VMALLOC_END);
         BUG_ON(!PAGE_ALIGNED(addr));

-       debug_check_no_locks_freed(mem, size);
-
         if (likely(count <= VMAP_MAX_ALLOC)) {
+               debug_check_no_locks_freed(mem, size);

It should have been 'va->va_start' instead of 'mem' in here but as
said before it looks correct to me but I am not really sure.

vb_free() doesn't honor va->va_start. If mem is not va_start and
deliberate, one will provide proper size. And that should be okay
to do as per the code. So, I don't think this particular debug_check
should have passed va_start in args.



Chintan
--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center,
Inc. is a member of the Code Aurora Forum, a Linux Foundation
Collaborative Project




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