Re: [PATCH stable] ipmi:msghandler: Fix potential memory corruption in ipmi_create_user()

[Brendan Jackman <jackmanb@google.com>]

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@linaro.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@linaro.org>
>> Message-ID: <aBjMZ8RYrOt6NOgi@stanley.mountain>
>> Signed-off-by: Corey Minyard <corey@minyard.net>
>> Signed-off-by: Brendan Jackman <jackmanb@google.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.