linux-kernel - Re: kmemleak detects leak in msr_build

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Message-ID: <41359b02-5f03-b822-9407-fb8d5ce44e70@molgen.mpg.de>
Date:   Tue, 11 Jan 2022 22:05:43 +0100
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        Catalin Marinas <catalin.marinas@....com>
Subject: Re: kmemleak detects leak in msr_build_context

Dear Dave,


Thank you for your quick reply.

Am 11.01.22 um 16:26 schrieb Dave Hansen:
> On 1/10/22 23:49, Paul Menzel wrote:
>> Running Linux from commit bf4eebf8cfa2 (Merge tag 
>> 'linux-kselftest-kunit-5.17-rc1' of 
>> git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest), 
>> kmemleak reported the leak below:
>>
>> ```
>> unreferenced object 0xffff8914823de500 (size 64):
>>    comm "swapper/0", pid 1, jiffies 4294667581 (age 1253.406s)
>>    hex dump (first 32 bytes):
>>      00 00 00 00 00 00 00 00 04 10 01 c0 00 00 00 00  ................
>>      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>    backtrace:
>>      [<000000007f3b05e9>] __kmalloc+0x177/0x330
>>      [<0000000008104cca>] msr_build_context.constprop.0+0x32/0xbe
>>      [<00000000012bab4e>] msr_save_cpuid_features+0x28/0x2f
>>      [<00000000b7a2262e>] pm_check_save_msr+0x2e/0x40
>>      [<00000000cbe9d92d>] do_one_initcall+0x44/0x200
>>      [<0000000094deab7b>] kernel_init_freeable+0x1fc/0x273
>>      [<00000000d3dbaa56>] kernel_init+0x16/0x160
>>      [<0000000058c4a8b3>] ret_from_fork+0x22/0x30
> 
> Thanks for the report.

Thank you for your quick response.

> I've taken a look through arch/x86/power/cpu.c, and nothing obvious 
> jumped out at me.  msr_build_context() could probably be cleaned up by 
> using kvrealloc(), but it hasn't been touched recently in a way that I 
> would expect things to leak.

Thank you for checking. I do not know if it’s a regression, as I didn’t 
watch out for that error in the last months.

> I suspect this is a false positive from kmemleak.

Maybe Catalin can check.

> If you could share your full dmesg, it might help spot something.  But, 
> I didn't see anything.

Please find it attached.

I am able to reproduce it doing `dpkg -i ../*deb` on the Linux packages 
built with `make bindeb-pkg`.


Kind regards,

Paul
View attachment "20220111-linux-5.16+-messages-kmemleak.txt" of type "text/plain" (146861 bytes)