Messages in this thread | | | From | Joel Fernandes <> | Date | Thu, 30 Mar 2017 23:49:52 -0700 | Subject | Re: [PATCH v2] module: check if memory leak by module. |
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Hi Michal,
On Wed, Mar 29, 2017 at 3:43 AM, Michal Hocko <mhocko@kernel.org> wrote: > On Wed 29-03-17 09:23:32, Vaneet Narang wrote: >> Hi, >> >> >> Hmm, how can you track _all_ vmalloc allocations done on behalf of the >> >> module? It is quite some time since I've checked kernel/module.c but >> >> from my vague understading your check is basically only about statically >> >> vmalloced areas by module loader. Is that correct? If yes then is this >> >> actually useful? Were there any bugs in the loader code recently? What >> >> led you to prepare this patch? All this should be part of the changelog! >> >> First of all there is no issue in kernel/module.c. This patch add functionality >> to detect scenario where some kernel module does some memory allocation but gets >> unloaded without doing vfree. For example >> static int kernel_init(void) >> { >> char * ptr = vmalloc(400 * 1024); >> return 0; >> } > > How can you track that allocation back to the module? Does this patch > actually works at all? Also why would be vmalloc more important than > kmalloc allocations?
Doesn't the patch use caller's (in this case, the module is the caller) text address for tracking this? vma->vm->caller should track the caller doing the allocation?
From the code: vmalloc -> __vmalloc_node_flags
In __vmalloc_node_flags: return __vmalloc_node(size, 1, flags, PAGE_KERNEL, node, __builtin_return_address(0));
Since __vmalloc_node_flags is marked as inline, I believe the __builtin_return_address(0) will return the return address of the original vmalloc() call which is in the module calling vmalloc.
Regards, Joel
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