linux-kernel - Re: [PATCH v2 1/3] tpm: efi: Use local variable for calculating final log size

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Message-ID: <39ea4fef-0a21-ad06-118f-dbdf01cd5c61@linux.ibm.com>
Date:   Thu, 11 Mar 2021 09:02:38 -0500
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     peterhuewe@....de, jgg@...pe.ca, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, mjg59@...gle.com
Subject: Re: [PATCH v2 1/3] tpm: efi: Use local variable for calculating final
 log size


On 3/10/21 6:24 PM, Jarkko Sakkinen wrote:
> On Thu, Mar 11, 2021 at 01:21:47AM +0200, Jarkko Sakkinen wrote:
>> On Wed, Mar 10, 2021 at 05:19:14PM -0500, Stefan Berger wrote:
>>> When tpm_read_log_efi is called multiple times, which happens when
>>> one loads and unloads a TPM2 driver multiple times, then the global
>>> variable efi_tpm_final_log_size will at some point become a negative
>>> number due to the subtraction of final_events_preboot_size occurring
>>> each time. Use a local variable to avoid this integer underflow.
>>>
>>> The following issue is now resolved:
>>>
>>> Mar  8 15:35:12 hibinst kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
>>> Mar  8 15:35:12 hibinst kernel: Workqueue: tpm-vtpm vtpm_proxy_work [tpm_vtpm_proxy]
>>> Mar  8 15:35:12 hibinst kernel: RIP: 0010:__memcpy+0x12/0x20
>>> Mar  8 15:35:12 hibinst kernel: Code: 00 b8 01 00 00 00 85 d2 74 0a c7 05 44 7b ef 00 0f 00 00 00 c3 cc cc cc 66 66 90 66 90 48 89 f8 48 89 d1 48 c1 e9 03 83 e2 07 <f3> 48 a5 89 d1 f3 a4 c3 66 0f 1f 44 00 00 48 89 f8 48 89 d1 f3 a4
>>> Mar  8 15:35:12 hibinst kernel: RSP: 0018:ffff9ac4c0fcfde0 EFLAGS: 00010206
>>> Mar  8 15:35:12 hibinst kernel: RAX: ffff88f878cefed5 RBX: ffff88f878ce9000 RCX: 1ffffffffffffe0f
>>> Mar  8 15:35:12 hibinst kernel: RDX: 0000000000000003 RSI: ffff9ac4c003bff9 RDI: ffff88f878cf0e4d
>>> Mar  8 15:35:12 hibinst kernel: RBP: ffff9ac4c003b000 R08: 0000000000001000 R09: 000000007e9d6073
>>> Mar  8 15:35:12 hibinst kernel: R10: ffff9ac4c003b000 R11: ffff88f879ad3500 R12: 0000000000000ed5
>>> Mar  8 15:35:12 hibinst kernel: R13: ffff88f878ce9760 R14: 0000000000000002 R15: ffff88f77de7f018
>>> Mar  8 15:35:12 hibinst kernel: FS:  0000000000000000(0000) GS:ffff88f87bd00000(0000) knlGS:0000000000000000
>>> Mar  8 15:35:12 hibinst kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> Mar  8 15:35:12 hibinst kernel: CR2: ffff9ac4c003c000 CR3: 00000001785a6004 CR4: 0000000000060ee0
>>> Mar  8 15:35:12 hibinst kernel: Call Trace:
>>> Mar  8 15:35:12 hibinst kernel: tpm_read_log_efi+0x152/0x1a7
>>> Mar  8 15:35:12 hibinst kernel: tpm_bios_log_setup+0xc8/0x1c0
>>> Mar  8 15:35:12 hibinst kernel: tpm_chip_register+0x8f/0x260
>>> Mar  8 15:35:12 hibinst kernel: vtpm_proxy_work+0x16/0x60 [tpm_vtpm_proxy]
>>> Mar  8 15:35:12 hibinst kernel: process_one_work+0x1b4/0x370
>>> Mar  8 15:35:12 hibinst kernel: worker_thread+0x53/0x3e0
>>> Mar  8 15:35:12 hibinst kernel: ? process_one_work+0x370/0x370
>>>
>>> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
>> Fixes tag for this one?
> Or just sanity check, I think it is:
>
> Fixes: 166a2809d65b ("tpm: Don't duplicate events from the final event log in the TCG2 log")
Looks good.
>
> Also, I guess all of the patches ought to have stable cc, right?

Yes, please. I think the maintainer has to add this 'at some point'.

Since you queued them already I won't send a v3.


Thanks!

    Stefan