From: Jarkko Sakkinen <jarkko@kernel.org>
To: Stefan Berger <stefanb@linux.ibm.com>
Cc: peterhuewe@gmx.de, jgg@ziepe.ca, linux-integrity@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] tpm: efi: Use local variable for calculating final log size
Date: Wed, 10 Mar 2021 21:47:04 +0200 [thread overview]
Message-ID: <YEkiONI7P32bH29i@kernel.org> (raw)
In-Reply-To: <20210309031954.6232-2-stefanb@linux.ibm.com>
On Mon, Mar 08, 2021 at 10:19:52PM -0500, Stefan Berger wrote:
> When tpm_read_log_efi was 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_efi_tpm_final_log_size 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@linux.ibm.com>
> ---
> drivers/char/tpm/eventlog/efi.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/char/tpm/eventlog/efi.c b/drivers/char/tpm/eventlog/efi.c
> index 35229e5143ca..b6ffb5faf416 100644
> --- a/drivers/char/tpm/eventlog/efi.c
> +++ b/drivers/char/tpm/eventlog/efi.c
> @@ -18,6 +18,7 @@ int tpm_read_log_efi(struct tpm_chip *chip)
>
> struct efi_tcg2_final_events_table *final_tbl = NULL;
> struct linux_efi_tpm_eventlog *log_tbl;
> + int local_efi_tpm_final_log_size;
> struct tpm_bios_log *log;
> u32 log_size;
> u8 tpm_log_version;
> @@ -80,10 +81,11 @@ int tpm_read_log_efi(struct tpm_chip *chip)
> goto out;
> }
>
> - efi_tpm_final_log_size -= log_tbl->final_events_preboot_size;
> + local_efi_tpm_final_log_size = efi_tpm_final_log_size -
> + log_tbl->final_events_preboot_size;
This starts to have so many weird locals that an inline comment here
in plain Enlighs would be nice explaining the calculation.
>
> tmp = krealloc(log->bios_event_log,
> - log_size + efi_tpm_final_log_size,
> + log_size + local_efi_tpm_final_log_size,
Ditto.
> GFP_KERNEL);
> if (!tmp) {
> kfree(log->bios_event_log);
> @@ -100,9 +102,9 @@ int tpm_read_log_efi(struct tpm_chip *chip)
> */
> memcpy((void *)log->bios_event_log + log_size,
> final_tbl->events + log_tbl->final_events_preboot_size,
> - efi_tpm_final_log_size);
> + local_efi_tpm_final_log_size);
> log->bios_event_log_end = log->bios_event_log +
> - log_size + efi_tpm_final_log_size;
> + log_size + local_efi_tpm_final_log_size;
Ditto.
>
> out:
> memunmap(final_tbl);
> --
> 2.29.2
>
>
I think this is good chance to improve the documentation a bit.
/Jarkko
next prev parent reply other threads:[~2021-03-10 19:48 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-09 3:19 [PATCH 0/3] Fix bugs related to TPM2 event log Stefan Berger
2021-03-09 3:19 ` [PATCH 1/3] tpm: efi: Use local variable for calculating final log size Stefan Berger
2021-03-10 19:47 ` Jarkko Sakkinen [this message]
2021-03-09 3:19 ` [PATCH 2/3] tpm: acpi: Check eventlog signature before using it Stefan Berger
2021-03-10 19:51 ` Jarkko Sakkinen
2021-03-09 3:19 ` [PATCH 3/3] tpm: vtpm_proxy: Avoid reading host log when using a virtual device Stefan Berger
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