linux-kernel - Re: [RFC 02/10] module: fix memory leak on early load

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Date:   Fri, 9 Dec 2016 18:06:44 +0100 (CET)
From:   Miroslav Benes <mbenes@...e.cz>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
cc:     shuah@...nel.org, jeyu@...hat.com, rusty@...tcorp.com.au,
        ebiederm@...ssion.com, dmitry.torokhov@...il.com, acme@...hat.com,
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        akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
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        linux-kernel@...r.kernel.org
Subject: Re: [RFC 02/10] module: fix memory leak on early load_module()
 failures

On Thu, 8 Dec 2016, Luis R. Rodriguez wrote:

> While looking for early possible module loading failures I was
> able to reproduce a memory leak possible with kmemleak. There
> are a few rare ways to trigger a failure:
> 
>   o we've run into a failure while processing kernel parameters
>     (parse_args() returns an error)
>   o mod_sysfs_setup() fails
>   o we're a live patch module and copy_module_elf() fails
> 
> Chances of running into this issue is really low.
> 
> kmemleak splat:
> 
> unreferenced object 0xffff9f2c4ada1b00 (size 32):
>   comm "kworker/u16:4", pid 82, jiffies 4294897636 (age 681.816s)
>   hex dump (first 32 bytes):
>     6d 65 6d 73 74 69 63 6b 30 00 00 00 00 00 00 00  memstick0.......
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffff8c6cfeba>] kmemleak_alloc+0x4a/0xa0
>     [<ffffffff8c200046>] __kmalloc_track_caller+0x126/0x230
>     [<ffffffff8c1bc581>] kstrdup+0x31/0x60
>     [<ffffffff8c1bc5d4>] kstrdup_const+0x24/0x30
>     [<ffffffff8c3c23aa>] kvasprintf_const+0x7a/0x90
>     [<ffffffff8c3b5481>] kobject_set_name_vargs+0x21/0x90
>     [<ffffffff8c4fbdd7>] dev_set_name+0x47/0x50
>     [<ffffffffc07819e5>] memstick_check+0x95/0x33c [memstick]
>     [<ffffffff8c09c893>] process_one_work+0x1f3/0x4b0
>     [<ffffffff8c09cb98>] worker_thread+0x48/0x4e0
>     [<ffffffff8c0a2b79>] kthread+0xc9/0xe0
>     [<ffffffff8c6dab5f>] ret_from_fork+0x1f/0x40
>     [<ffffffffffffffff>] 0xffffffffffffffff
> 
> Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>

Reviewed-by: Miroslav Benes <mbenes@...e.cz>

What about

Fixes: e180a6b7759a ("param: fix charp parameters set via sysfs")

?

Miroslav

> ---
>  kernel/module.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/module.c b/kernel/module.c
> index f7482db0f843..e420ed67e533 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3722,6 +3722,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
>  	mod_sysfs_teardown(mod);
>   coming_cleanup:
>  	mod->state = MODULE_STATE_GOING;
> +	destroy_params(mod->kp, mod->num_kp);
>  	blocking_notifier_call_chain(&module_notify_list,
>  				     MODULE_STATE_GOING, mod);
>  	klp_module_going(mod);
> -- 
> 2.10.1
>