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Date: Tue, 3 Apr 2012 10:06:31 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Bruno =?iso-8859-1?Q?Pr=E9mont?= <bonbons@linux-vserver.org>
Cc: Greg KH <gregkh@linuxfoundation.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Peter Zijlstra <peterz@infradead.org>, linux-kernel@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v2a] sysfs: Prevent crash on unset sysfs group attributes
Message-ID: <20120403080631.GA29929@gmail.com>
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* Bruno Prémont <bonbons@linux-vserver.org> wrote:

> Do not let the kernel crash when a device is registered with
> sysfs while group attributes are not set (aka NULL).
> 
> Warn about the offender with some information about the offending
> device.
> 
> This would warn instead of trying NULL pointer deref like:
>  BUG: unable to handle kernel NULL pointer dereference at (null)
>  IP: [<ffffffff81152673>] internal_create_group+0x83/0x1a0
>  PGD 0
>  Oops: 0000 [#1] SMP
>  CPU 0
>  Modules linked in:
> 
>  Pid: 1, comm: swapper/0 Not tainted 3.4.0-rc1-x86_64 #3 HP ProLiant DL360 G4
>  RIP: 0010:[<ffffffff81152673>]  [<ffffffff81152673>] internal_create_group+0x83/0x1a0
>  RSP: 0018:ffff88019485fd70  EFLAGS: 00010202
>  RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0000000000000001
>  RDX: ffff880192e99908 RSI: ffff880192e99630 RDI: ffffffff81a26c60
>  RBP: ffff88019485fdc0 R08: 0000000000000000 R09: 0000000000000000
>  R10: ffff880192e99908 R11: 0000000000000000 R12: ffffffff81a16a00
>  R13: ffff880192e99908 R14: ffffffff81a16900 R15: 0000000000000000
>  FS:  0000000000000000(0000) GS:ffff88019bc00000(0000) knlGS:0000000000000000
>  CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
>  CR2: 0000000000000000 CR3: 0000000001a0c000 CR4: 00000000000007f0
>  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>  DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
>  Process swapper/0 (pid: 1, threadinfo ffff88019485e000, task ffff880194878000)
>  Stack:
>   ffff88019485fdd0 ffff880192da9d60 0000000000000000 ffff880192e99908
>   ffff880192e995d8 0000000000000001 ffffffff81a16a00 ffff880192da9d60
>   0000000000000000 0000000000000000 ffff88019485fdd0 ffffffff811527be
>  Call Trace:
>   [<ffffffff811527be>] sysfs_create_group+0xe/0x10
>   [<ffffffff81376ca6>] device_add_groups+0x46/0x80
>   [<ffffffff81377d3d>] device_add+0x46d/0x6a0
>   ...
>     
> Signed-off-by: Bruno Prémont <bonbons@linux-vserver.org>

Still-Acked-by: Ingo Molnar <mingo@elte.hu>

Thanks,

	Ingo