• Jerry Snitselaar's avatar
    efi/tpm: Only set 'efi_tpm_final_log_size' after successful event log parsing · e658c82b
    Jerry Snitselaar authored
    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: default avatarJerry Snitselaar <jsnitsel@redhat.com>
    Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
    Cc: Ben Dooks <ben.dooks@codethink.co.uk>
    Cc: Dave Young <dyoung@redhat.com>
    Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Lukas Wunner <lukas@wunner.de>
    Cc: Lyude Paul <lyude@redhat.com>
    Cc: Matthew Garrett <mjg59@google.com>
    Cc: Octavian Purdila <octavian.purdila@intel.com>
    Cc: Peter Jones <pjones@redhat.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: c46f3405 ("tpm: Reserve the TPM final events table")
    Link: https://lkml.kernel.org/r/20191002165904.8819-6-ard.biesheuvel@linaro.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    e658c82b
tpm.c 2.42 KB