linux-kernel - Re: [PATCH] kasan: fix kmemleak false-positive in kasan_module

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Message-ID: <CAHkRjk7_2udHhf-MmsF4uvusYR+b17jLGoL=5OzOdDXQAiC_9w@mail.gmail.com>
Date:	Tue, 17 Nov 2015 16:29:49 +0000
From:	Catalin Marinas <catalin.marinas@...il.com>
To:	Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kasan: fix kmemleak false-positive in kasan_module_alloc()

On 17 November 2015 at 16:20, Andrey Ryabinin <aryabinin@...tuozzo.com> wrote:
> kasan_module_alloc() allocates shadow memory for module and frees it on module
> unloading. It doesn't store the pointer to allocated shadow memory because
> it could be calculated from the shadowed address, i.e. kasan_mem_to_shadow(addr).
> Since kmemleak cannot find pointer to allocated shadow, it thinks that memory leaked.
> We should tell kmemleak that this is not a leak.
[...]
> @@ -444,6 +445,7 @@ int kasan_module_alloc(void *addr, size_t size)
>
>         if (ret) {
>                 find_vm_area(addr)->flags |= VM_KASAN;
> +               kmemleak_not_leak(ret);
>                 return 0;
>         }

If such memory does not contain any pointers to other objects, you
could use kmemleak_ignore() which would make kmemleak not scan it at
all (slight performance improvement).

-- 
Catalin
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