linux-kernel - Re: V3.10-rc1 memory leak

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Date:	Wed, 15 May 2013 09:49:50 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Catalin Marinas <catalin.marinas@....com>, rjw@...k.pl
Cc:	Larry Finger <Larry.Finger@...inger.net>,
	Steven Rostedt <rostedt@...dmis.org>,
	"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-acpi@...r.kernel.org
Subject: Re: V3.10-rc1 memory leak

On Wed, 2013-05-15 at 16:02 +0100, Catalin Marinas wrote:
> On Wed, May 15, 2013 at 04:15:46AM +0100, Larry Finger wrote:
> > I do not see that particular one; however, I see 4 instances of
> > 
> > unreferenced object 0xffff8800b7979750 (size 8):
> >    comm "swapper/0", pid 1, jiffies 4294892402 (age 21888.316s)
> >    hex dump (first 8 bytes):
> >      31 38 00 b7 00 88 ff ff                          18......
> >    backtrace:
> >      [<ffffffff81432ea1>] kmemleak_alloc+0x21/0x50
> >      [<ffffffff81145d50>] __kmalloc_track_caller+0x140/0x2b0
> >      [<ffffffff81119fb5>] kstrdup+0x35/0x70
> >      [<ffffffff8125febc>] acpi_set_pnp_ids+0xd0/0x304
> >      [<ffffffff81260c47>] acpi_scan_init_hotplug+0x47/0xa1
> >      [<ffffffff81261223>] acpi_bus_check_add+0x66/0xd7
> >      [<ffffffff8127877a>] acpi_ns_walk_namespace+0xb9/0x173
> >      [<ffffffff81278bf3>] acpi_walk_namespace+0x93/0xc6
> >      [<ffffffff812612dc>] acpi_bus_scan+0x48/0x9a
> >      [<ffffffff818c983d>] acpi_scan_init+0x57/0x14b
> >      [<ffffffff818c966a>] acpi_init+0x244/0x286
> >      [<ffffffff810002fa>] do_one_initcall+0x10a/0x160
> >      [<ffffffff8189cef0>] kernel_init_freeable+0x103/0x192
> >      [<ffffffff814313a9>] kernel_init+0x9/0xf0
> >      [<ffffffff8144992c>] ret_from_fork+0x7c/0xb0
> >      [<ffffffffffffffff>] 0xffffffffffffffff
> > 
> > All four were allocated early in the bootup, and are the only leaks reported in 
> > my system. I have not yet tested to see if they are false.
> 
> This looks to me like a real leak, possibly introduced by commit
> 6b772e8f9 (ACPI: Update PNPID match handling for notify). The
> acpi_scan_init_hotplug() function calls acpi_set_pnp_ids() which
> allocates pnp.unique_id (kstrdup()) but for some reason it fails and
> does not set pnp.type.hardware_id. The return does not call
> acpi_free_pnp_ids() which would be responsible for such freeing.

I agree with your analysis.  It appears that this ACPI device object has
_UID but not _HID.  ACPI spec defines that _UID is a unique ID among a
same _HID.  So, it is odd to have _UID without _HID.  But, nonetheless,
this case needs to be handled as such systems exist.

> Something like below, but not tested and may fail some NULL pointer
> checks:

The change looks good.  acpi_free_pnp_ids() handles this empty list
pnp->ids properly.  Are you going to submit this patch with your
signed-off?

Thanks!
-Toshi

> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index fe158fd..c1bc608 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -1785,7 +1785,7 @@ static void acpi_scan_init_hotplug(acpi_handle handle, int type)
>  	acpi_set_pnp_ids(handle, &pnp, type);
>  
>  	if (!pnp.type.hardware_id)
> -		return;
> +		goto out;
>  
>  	/*
>  	 * This relies on the fact that acpi_install_notify_handler() will not
> @@ -1800,6 +1800,7 @@ static void acpi_scan_init_hotplug(acpi_handle handle, int type)
>  		}
>  	}
>  
> +out:
>  	acpi_free_pnp_ids(&pnp);
>  }
>  


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