linux-kernel - Re: [PATCH] selinux: fix memory leak in sel_make

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Date:	Thu, 13 Aug 2009 14:55:15 -0400
From:	Paul Moore <paul.moore@...com>
To:	Xiaotian Feng <dfeng@...hat.com>
Cc:	jmorris@...ei.org, eparis@...isplace.org, sds@...ho.nsa.gov,
	serue@...ibm.com, linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selinux: fix memory leak in sel_make_bools

On Thursday 13 August 2009 04:26:16 am Xiaotian Feng wrote:
> In sel_make_bools, kernel allocates memory for bool_pending_names[i]
> with security_get_bools. So if we just free bool_pending_names, those
> memories for bool_pending_names[i] will be leaked.
>
> This patch resolves dozens of following kmemleak report after resuming
> from suspend:
> unreferenced object 0xffff88022e4c7380 (size 32):
>   comm "init", pid 1, jiffies 4294677173
>   backtrace:
>     [<ffffffff810f76b5>] create_object+0x1a2/0x2a9
>     [<ffffffff810f78bb>] kmemleak_alloc+0x26/0x4b
>     [<ffffffff810ef3eb>] __kmalloc+0x18f/0x1b8
>     [<ffffffff811cd511>] security_get_bools+0xd7/0x16f
>     [<ffffffff811c48c0>] sel_write_load+0x12e/0x62b
>     [<ffffffff810f9a39>] vfs_write+0xae/0x10b
>     [<ffffffff810f9b56>] sys_write+0x4a/0x6e
>     [<ffffffff81011b82>] system_call_fastpath+0x16/0x1b
>     [<ffffffffffffffff>] 0xffffffffffffffff
>
> Signed-off-by: Xiaotian Feng <dfeng@...hat.com>
> ---
>  security/selinux/selinuxfs.c |    6 +++++-
>  1 files changed, 5 insertions(+), 1 deletions(-)
>
> diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
> index b4fc506..ab93472 100644
> --- a/security/selinux/selinuxfs.c
> +++ b/security/selinux/selinuxfs.c
> @@ -979,7 +979,11 @@ static int sel_make_bools(void)
>  	u32 sid;
>
>  	/* remove any existing files */
> -	kfree(bool_pending_names);
> +	if (bool_pending_names) {
> +		for (i = 0; i < bool_num; i++)
> +			kfree(bool_pending_names[i]);
> +		kfree(bool_pending_names);
> +	}
>  	kfree(bool_pending_values);
>  	bool_pending_names = NULL;
>  	bool_pending_values = NULL;

Since the code seems to rely on 'bool_num' in other places to ensure we don't 
walk off the end of the array it is probably safe to omit the 'if 
(bool_pending_names) ...' conditional and just rely on the for loop to do the 
right thing.

-- 
paul moore
linux @ hp

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