If __calc_tpm2_event_size fails to parse an event it will return 0, resulting tpm2_calc_event_log_size returning -1. Currently there is no check of this return value, and efi_tpm_final_log_size can end up being set to this negative value resulting in a panic like the the one given below.

This has been reported with a number of systems now from different vendors. In the case of the system I have access to the hash algorithm id associated with an event isn't in the TCG registry, and a match isn't found when walking the digest sizes array resulting in 0 being returned by __calc_tpm2_event_size. There are a number of other points in __calc_tpm2_event_size where it could potentially return 0 and trigger the same outcome.

[ 0.774340] BUG: unable to handle page fault for address: ffffbc8fc00866ad [ 0.774788] #PF: supervisor read access in kernel mode [ 0.774788] #PF: error_code(0x0000) - not-present page [ 0.774788] PGD 107d36067 P4D 107d36067 PUD 107d37067 PMD 107d38067 PTE 0 [ 0.774788] Oops: 0000 [#1] SMP PTI [ 0.774788] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.3.0-0.rc2.1.elrdy.x86_64 #1 [ 0.774788] Hardware name: LENOVO 20HGS22D0W/20HGS22D0W, BIOS N1WET51W (1.30 ) 09/14/2018 [ 0.774788] RIP: 0010:memcpy_erms+0x6/0x10 [ 0.774788] Code: 90 90 90 90 eb 1e 0f 1f 00 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 c3 0f 1f 80 00 00 00 00 48 89 f8 48 83 fa 20 72 7e 40 38 fe [ 0.774788] RSP: 0000:ffffbc8fc0073b30 EFLAGS: 00010286 [ 0.774788] RAX: ffff9b1fc7c5b367 RBX: ffff9b1fc8390000 RCX: ffffffffffffe962 [ 0.774788] RDX: ffffffffffffe962 RSI: ffffbc8fc00866ad RDI: ffff9b1fc7c5b367 [ 0.774788] RBP: ffff9b1c10ca7018 R08: ffffbc8fc0085fff R09: 8000000000000063 [ 0.774788] R10: 0000000000001000 R11: 000fffffffe00000 R12: 0000000000003367 [ 0.774788] R13: ffff9b1fcc47c010 R14: ffffbc8fc0085000 R15: 0000000000000002 [ 0.774788] FS: 0000000000000000(0000) GS:ffff9b1fce200000(0000) knlGS:0000000000000000 [ 0.774788] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 0.774788] CR2: ffffbc8fc00866ad CR3: 000000029f60a001 CR4: 00000000003606f0 [ 0.774788] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 0.774788] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 0.774788] Call Trace: [ 0.774788] tpm_read_log_efi+0x156/0x1a0 [ 0.774788] tpm_bios_log_setup+0xc8/0x190 [ 0.774788] tpm_chip_register+0x50/0x1c0 [ 0.774788] tpm_tis_core_init.cold.9+0x28c/0x466 [ 0.774788] tpm_tis_plat_probe+0xcc/0xea [ 0.774788] platform_drv_probe+0x35/0x80 [ 0.774788] really_probe+0xef/0x390 [ 0.774788] driver_probe_device+0xb4/0x100 [ 0.774788] device_driver_attach+0x4f/0x60 [ 0.774788] __driver_attach+0x86/0x140 [ 0.774788] ? device_driver_attach+0x60/0x60 [ 0.774788] bus_for_each_dev+0x76/0xc0 [ 0.774788] ? klist_add_tail+0x3b/0x70 [ 0.774788] bus_add_driver+0x14a/0x1e0 [ 0.774788] ? tpm_init+0xea/0xea [ 0.774788] ? do_early_param+0x8e/0x8e [ 0.774788] driver_register+0x6b/0xb0 [ 0.774788] ? tpm_init+0xea/0xea [ 0.774788] init_tis+0x86/0xd8 [ 0.774788] ? do_early_param+0x8e/0x8e [ 0.774788] ? driver_register+0x94/0xb0 [ 0.774788] do_one_initcall+0x46/0x1e4 [ 0.774788] ? do_early_param+0x8e/0x8e [ 0.774788] kernel_init_freeable+0x199/0x242 [ 0.774788] ? rest_init+0xaa/0xaa [ 0.774788] kernel_init+0xa/0x106 [ 0.774788] ret_from_fork+0x35/0x40 [ 0.774788] Modules linked in: [ 0.774788] CR2: ffffbc8fc00866ad [ 0.774788] ---[ end trace 42930799f8d6eaea ]--- [ 0.774788] RIP: 0010:memcpy_erms+0x6/0x10 [ 0.774788] Code: 90 90 90 90 eb 1e 0f 1f 00 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 c3 0f 1f 80 00 00 00 00 48 89 f8 48 83 fa 20 72 7e 40 38 fe [ 0.774788] RSP: 0000:ffffbc8fc0073b30 EFLAGS: 00010286 [ 0.774788] RAX: ffff9b1fc7c5b367 RBX: ffff9b1fc8390000 RCX: ffffffffffffe962 [ 0.774788] RDX: ffffffffffffe962 RSI: ffffbc8fc00866ad RDI: ffff9b1fc7c5b367 [ 0.774788] RBP: ffff9b1c10ca7018 R08: ffffbc8fc0085fff R09: 8000000000000063 [ 0.774788] R10: 0000000000001000 R11: 000fffffffe00000 R12: 0000000000003367 [ 0.774788] R13: ffff9b1fcc47c010 R14: ffffbc8fc0085000 R15: 0000000000000002 [ 0.774788] FS: 0000000000000000(0000) GS:ffff9b1fce200000(0000) knlGS:0000000000000000 [ 0.774788] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 0.774788] CR2: ffffbc8fc00866ad CR3: 000000029f60a001 CR4: 00000000003606f0 [ 0.774788] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 0.774788] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 0.774788] Kernel panic - not syncing: Fatal exception [ 0.774788] Kernel Offset: 0x1d000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) [ 0.774788] ---[ end Kernel panic - not syncing: Fatal exception ]---

Also __calc_tpm2_event_size returns a size of 0 when it fails to parse an event, so update function documentation to reflect this.

Fixes: c46f3405692de ("tpm: Reserve the TPM final events table") Cc: linux-efi@vger.kernel.org Cc: linux-integrity@vger.kernel.org Cc: stable@vger.kernel.org Cc: Matthew Garrett mjg59@google.com Cc: Ard Biesheuvel ard.biesheuvel@linaro.org Cc: Jarkko Sakkinen jarkko.sakkinen@linux.intel.com Signed-off-by: Jerry Snitselaar jsnitsel@redhat.com --- v2: added FW_BUG to pr_err, and renamed label to out_calc. Also updated comment for __calc_tpm2_event_size to properly state that returning 0 is failure.

drivers/firmware/efi/tpm.c | 11 ++++++++--- include/linux/tpm_eventlog.h | 2 +- 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/firmware/efi/tpm.c b/drivers/firmware/efi/tpm.c index 1d3f5ca3eaaf..284da9242a4f 100644 --- a/drivers/firmware/efi/tpm.c +++ b/drivers/firmware/efi/tpm.c @@ -40,8 +40,7 @@ int __init efi_tpm_eventlog_init(void) { struct linux_efi_tpm_eventlog *log_tbl; struct efi_tcg2_final_events_table *final_tbl; - unsigned int tbl_size; - int ret = 0; + int tbl_size, ret = 0;

if (efi.tpm_log == EFI_INVALID_TABLE_ADDR) { /* @@ -80,11 +79,17 @@ int __init efi_tpm_eventlog_init(void) + sizeof(final_tbl->nr_events), final_tbl->nr_events, log_tbl->log); + if (tbl_size < 0) { + pr_err(FW_BUG "Failed to parse event in TPM Final Event log\n"); + goto out_calc; + } + memblock_reserve((unsigned long)final_tbl, tbl_size + sizeof(*final_tbl)); - early_memunmap(final_tbl, sizeof(*final_tbl)); efi_tpm_final_log_size = tbl_size;

+out_calc: + early_memunmap(final_tbl, sizeof(*final_tbl)); out: early_memunmap(log_tbl, sizeof(*log_tbl)); return ret; diff --git a/include/linux/tpm_eventlog.h b/include/linux/tpm_eventlog.h index 63238c84dc0b..7388ef0ce483 100644 --- a/include/linux/tpm_eventlog.h +++ b/include/linux/tpm_eventlog.h @@ -152,7 +152,7 @@ struct tcg_algorithm_info { * total. Once we've done this we know the offset of the data length field, * and can calculate the total size of the event. * - * Return: size of the event on success, <0 on failure + * Return: size of the event on success, 0 on failure */

static inline int __calc_tpm2_event_size(struct tcg_pcr_event2_head *event,