linux-efi.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
* [PATCH 1/2] efi+tpm: Don't access event->count when it isn't mapped.
@ 2019-08-26 15:30 Peter Jones
  2019-08-26 15:30 ` [PATCH 2/2] efi+tpm: don't traverse an event log with no events Peter Jones
                   ` (2 more replies)
  0 siblings, 3 replies; 13+ messages in thread
From: Peter Jones @ 2019-08-26 15:30 UTC (permalink / raw)
  To: Ard Biesheuvel
  Cc: Jarkko Sakkinen, Roberto Sassu, Matthew Garrett,
	Bartosz Szczepanek, Lyude Paul, linux-efi, linux-kernel,
	Peter Jones

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.

Signed-off-by: Peter Jones <pjones@redhat.com>
Tested-by: Lyude Paul <lyude@redhat.com>
---
 include/linux/tpm_eventlog.h | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/include/linux/tpm_eventlog.h b/include/linux/tpm_eventlog.h
index 63238c84dc0..549dab0b56b 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 = event->count;
+	event_type = 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);
-- 
2.23.0.rc2


^ permalink raw reply related	[flat|nested] 13+ messages in thread

end of thread, other threads:[~2019-08-31 16:46 UTC | newest]

Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-26 15:30 [PATCH 1/2] efi+tpm: Don't access event->count when it isn't mapped Peter Jones
2019-08-26 15:30 ` [PATCH 2/2] efi+tpm: don't traverse an event log with no events Peter Jones
2019-08-26 16:30   ` Jarkko Sakkinen
2019-08-26 17:45     ` Matthew Garrett
2019-08-31 16:46   ` Ard Biesheuvel
2019-08-26 16:28 ` [PATCH 1/2] efi+tpm: Don't access event->count when it isn't mapped Jarkko Sakkinen
2019-08-26 17:44   ` Matthew Garrett
2019-08-27 11:03     ` Jarkko Sakkinen
2019-08-27 13:41       ` Jarkko Sakkinen
2019-08-27 16:00         ` Matthew Garrett
2019-08-27 22:11         ` Peter Jones
2019-08-29 13:21           ` Jarkko Sakkinen
2019-08-31 16:11 ` Ard Biesheuvel

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).