linux-kernel - Re: [PATCH stable] ipmi:msghandler: Fix potential memory corruption in ipmi_create

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Message-ID: <DB0OMYW0QFR0.33PUE4BU0XS5D@google.com>
Date: Tue, 01 Jul 2025 11:29:59 +0000
From: Brendan Jackman <jackmanb@...gle.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: <stable@...r.kernel.org>, Corey Minyard <minyard@....org>, 
	Corey Minyard <cminyard@...sta.com>, <openipmi-developer@...ts.sourceforge.net>, 
	<linux-kernel@...r.kernel.org>, Dan Carpenter <dan.carpenter@...aro.org>, 
	Corey Minyard <corey@...yard.net>
Subject: Re: [PATCH stable] ipmi:msghandler: Fix potential memory corruption
 in ipmi_create_user()

On Tue Jul 1, 2025 at 10:14 AM UTC, Greg KH wrote:
> On Tue, Jul 01, 2025 at 09:52:55AM +0000, Brendan Jackman wrote:
>> On Mon Jun 30, 2025 at 6:10 PM UTC, Greg KH wrote:
>> > On Mon, Jun 30, 2025 at 05:09:02PM +0000, Brendan Jackman wrote:
>> >> From: Dan Carpenter <dan.carpenter@...aro.org>
>> >> 
>> >> commit fa332f5dc6fc662ad7d3200048772c96b861cf6b upstream
>> >> 
>> >> The "intf" list iterator is an invalid pointer if the correct
>> >> "intf->intf_num" is not found.  Calling atomic_dec(&intf->nr_users) on
>> >> and invalid pointer will lead to memory corruption.
>> >> 
>> >> We don't really need to call atomic_dec() if we haven't called
>> >> atomic_add_return() so update the if (intf->in_shutdown) path as well.
>> >> 
>> >> Fixes: 8e76741c3d8b ("ipmi: Add a limit on the number of users that may use IPMI")
>> >> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
>> >> Message-ID: <aBjMZ8RYrOt6NOgi@...nley.mountain>
>> >> Signed-off-by: Corey Minyard <corey@...yard.net>
>> >> Signed-off-by: Brendan Jackman <jackmanb@...gle.com>
>> >> ---
>> >> I have tested this in 6.12 with Google's platform drivers added to
>> >> reproduce the bug.  The bug causes the panic notifier chain to get
>> >> corrupted leading to a crash. With the fix this goes away.
>> >> 
>> >> Applies to 6.6 too but I haven't tested it there.
>> >
>> > So what kernels are you wanting this to be applied to?
>> 
>> Right, sorry for the ambiguity.  I've just applied the patch to 6.6 and
>> booted QEMU and it worked fine.
>> 
>> I have not reproduced a crash in 6.6 but it's pretty clearly a real bug
>> (it decrements the target of an uninitialized pointer).
>> 
>> So if you're OK with that then please apply to 6.6 and 6.12. Otherwise
>> just 6.12 is fine, I will send another PATCH if I ever hit the issue for
>> real in 6.6.
>
> But why would we skip 6.15.y?  

Ah, sorry. I forgot that existed (I was conflating "longterm" and
"stable" in my mind).

I've just applied this patch to 6.15.y and booted QEMU, seems OK.

Aaand now this made me realise I also forgot 6.1 existed and it also
has the bug. So I've just applied it to 6.1.y and booted that in QEMU
too.

So: 6.15, 6.12, 6.6, and 6.1.