From 047d50aee341d940350897c85799e56ae57c3849 Mon Sep 17 00:00:00 2001 From: Peter Jones Date: Wed, 2 Oct 2019 18:59:00 +0200 Subject: efi/tpm: Don't access event->count when it isn't mapped Some machines generate a lot of event log entries. When we're iterating over them, the code removes the old mapping and adds a new one, so once we cross the page boundary we're unmapping the page with the count on it. Hilarity ensues. This patch keeps the info from the header in local variables so we don't need to access that page again or keep track of if it's mapped. Tested-by: Lyude Paul Signed-off-by: Peter Jones Signed-off-by: Jarkko Sakkinen Signed-off-by: Ard Biesheuvel Reviewed-by: Jarkko Sakkinen Acked-by: Matthew Garrett Acked-by: Ard Biesheuvel Cc: Ben Dooks Cc: Dave Young Cc: Jerry Snitselaar Cc: Linus Torvalds Cc: Lukas Wunner Cc: Octavian Purdila Cc: Peter Zijlstra Cc: Scott Talbert Cc: Thomas Gleixner Cc: linux-efi@vger.kernel.org Cc: linux-integrity@vger.kernel.org Cc: stable@vger.kernel.org Fixes: 44038bc514a2 ("tpm: Abstract crypto agile event size calculations") Link: https://lkml.kernel.org/r/20191002165904.8819-4-ard.biesheuvel@linaro.org [ Minor edits. ] Signed-off-by: Ingo Molnar --- include/linux/tpm_eventlog.h | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) (limited to 'include') diff --git a/include/linux/tpm_eventlog.h b/include/linux/tpm_eventlog.h index 63238c84dc0b..b50cc3adca18 100644 --- a/include/linux/tpm_eventlog.h +++ b/include/linux/tpm_eventlog.h @@ -170,6 +170,7 @@ static inline int __calc_tpm2_event_size(struct tcg_pcr_event2_head *event, u16 halg; int i; int j; + u32 count, event_type; marker = event; marker_start = marker; @@ -190,16 +191,22 @@ static inline int __calc_tpm2_event_size(struct tcg_pcr_event2_head *event, } event = (struct tcg_pcr_event2_head *)mapping; + /* + * The loop below will unmap these fields if the log is larger than + * one page, so save them here for reference: + */ + count = READ_ONCE(event->count); + event_type = READ_ONCE(event->event_type); efispecid = (struct tcg_efi_specid_event_head *)event_header->event; /* Check if event is malformed. */ - if (event->count > efispecid->num_algs) { + if (count > efispecid->num_algs) { size = 0; goto out; } - for (i = 0; i < event->count; i++) { + for (i = 0; i < count; i++) { halg_size = sizeof(event->digests[i].alg_id); /* Map the digest's algorithm identifier */ @@ -256,8 +263,9 @@ static inline int __calc_tpm2_event_size(struct tcg_pcr_event2_head *event, + event_field->event_size; size = marker - marker_start; - if ((event->event_type == 0) && (event_field->event_size == 0)) + if (event_type == 0 && event_field->event_size == 0) size = 0; + out: if (do_mapping) TPM_MEMUNMAP(mapping, mapping_size); -- cgit v1.2.3 From e658c82be5561412c5e83b5e74e9da4830593f3e Mon Sep 17 00:00:00 2001 From: Jerry Snitselaar Date: Wed, 2 Oct 2019 18:59:02 +0200 Subject: efi/tpm: Only set 'efi_tpm_final_log_size' after successful event log parsing 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 crash like this one: BUG: unable to handle page fault for address: ffffbc8fc00866ad #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page RIP: 0010:memcpy_erms+0x6/0x10 Call Trace: tpm_read_log_efi() tpm_bios_log_setup() tpm_chip_register() tpm_tis_core_init.cold.9+0x28c/0x466 tpm_tis_plat_probe() platform_drv_probe() ... Also __calc_tpm2_event_size() returns a size of 0 when it fails to parse an event, so update function documentation to reflect this. The root cause of the issue that caused the failure of event parsing in this case is resolved by Peter Jone's patchset dealing with large event logs where crossing over a page boundary causes the page with the event count to be unmapped. Signed-off-by: Jerry Snitselaar Signed-off-by: Ard Biesheuvel Cc: Ben Dooks Cc: Dave Young Cc: Jarkko Sakkinen Cc: Linus Torvalds Cc: Lukas Wunner Cc: Lyude Paul Cc: Matthew Garrett Cc: Octavian Purdila Cc: Peter Jones Cc: Peter Zijlstra Cc: Scott Talbert Cc: Thomas Gleixner Cc: linux-efi@vger.kernel.org Cc: linux-integrity@vger.kernel.org Cc: stable@vger.kernel.org Fixes: c46f3405692de ("tpm: Reserve the TPM final events table") Link: https://lkml.kernel.org/r/20191002165904.8819-6-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar --- drivers/firmware/efi/tpm.c | 9 ++++++++- include/linux/tpm_eventlog.h | 2 +- 2 files changed, 9 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/drivers/firmware/efi/tpm.c b/drivers/firmware/efi/tpm.c index b9ae5c6f9b9c..703469c1ab8e 100644 --- a/drivers/firmware/efi/tpm.c +++ b/drivers/firmware/efi/tpm.c @@ -85,11 +85,18 @@ int __init efi_tpm_eventlog_init(void) final_tbl->nr_events, log_tbl->log); } + + if (tbl_size < 0) { + pr_err(FW_BUG "Failed to parse event in TPM Final Events 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 b50cc3adca18..131ea1bad458 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, -- cgit v1.2.3