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efi/tpm: Don't traverse an event log with no events
authorPeter Jones <pjones@redhat.com>
Wed, 2 Oct 2019 16:59:01 +0000 (18:59 +0200)
committerIngo Molnar <mingo@kernel.org>
Mon, 7 Oct 2019 13:24:35 +0000 (15:24 +0200)
When there are no entries to put into the final event log, some machines
will return the template they would have populated anyway.  In this case
the nr_events field is 0, but the rest of the log is just garbage.

This patch stops us from trying to iterate the table with
__calc_tpm2_event_size() when the number of events in the table is 0.

Tested-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Acked-by: Matthew Garrett <mjg59@google.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ben Dooks <ben.dooks@codethink.co.uk>
Cc: Dave Young <dyoung@redhat.com>
Cc: Jerry Snitselaar <jsnitsel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Lukas Wunner <lukas@wunner.de>
Cc: Octavian Purdila <octavian.purdila@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Scott Talbert <swt@techie.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Cc: linux-integrity@vger.kernel.org
Cc: stable@vger.kernel.org
Fixes: c46f3405692d ("tpm: Reserve the TPM final events table")
Link: https://lkml.kernel.org/r/20191002165904.8819-5-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
drivers/firmware/efi/tpm.c

index 1d3f5ca..b9ae5c6 100644 (file)
@@ -75,11 +75,16 @@ int __init efi_tpm_eventlog_init(void)
                goto out;
        }
 
-       tbl_size = tpm2_calc_event_log_size((void *)efi.tpm_final_log
-                                           + sizeof(final_tbl->version)
-                                           + sizeof(final_tbl->nr_events),
-                                           final_tbl->nr_events,
-                                           log_tbl->log);
+       tbl_size = 0;
+       if (final_tbl->nr_events != 0) {
+               void *events = (void *)efi.tpm_final_log
+                               + sizeof(final_tbl->version)
+                               + sizeof(final_tbl->nr_events);
+
+               tbl_size = tpm2_calc_event_log_size(events,
+                                                   final_tbl->nr_events,
+                                                   log_tbl->log);
+       }
        memblock_reserve((unsigned long)final_tbl,
                         tbl_size + sizeof(*final_tbl));
        early_memunmap(final_tbl, sizeof(*final_tbl));