efi/libstub/tpm: Initialize pointer variables to zero for mixed mode

[Linux-MTD Mailing List]

Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=79832f0b5f718e0023d9dd73e6845310609a564d
Commit:     79832f0b5f718e0023d9dd73e6845310609a564d
Parent:     fc6eabbbf8ef99efed778dd5afabc83c21dba585
Author:     Ard Biesheuvel <ard.biesheuvel at linaro.org>
AuthorDate: Tue Mar 13 14:09:21 2018 +0000
Committer:  Ingo Molnar <mingo at kernel.org>
CommitDate: Tue Mar 13 15:28:29 2018 +0100

    efi/libstub/tpm: Initialize pointer variables to zero for mixed mode
    
    As reported by Jeremy Cline, running the new TPM libstub code in mixed
    mode (i.e., 64-bit kernel on 32-bit UEFI) results in hangs when invoking
    the TCG2 protocol, or when accessing the log_tbl pool allocation.
    
    The reason turns out to be that in both cases, the 64-bit pointer
    variables are not fully initialized by the 32-bit EFI code, and so
    we should take care to zero initialize these variables beforehand,
    or we'll end up dereferencing bogus pointers.
    
    Reported-by: Jeremy Cline <jeremy at jcline.org>
    Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
    Cc: Linus Torvalds <torvalds at linux-foundation.org>
    Cc: Peter Zijlstra <peterz at infradead.org>
    Cc: Thomas Gleixner <tglx at linutronix.de>
    Cc: hdegoede at redhat.com
    Cc: jarkko.sakkinen at linux.intel.com
    Cc: javierm at redhat.com
    Cc: linux-efi at vger.kernel.org
    Cc: tweek at google.com
    Link: http://lkml.kernel.org/r/20180313140922.17266-2-ard.biesheuvel@linaro.org
    Signed-off-by: Ingo Molnar <mingo at kernel.org>
---
 drivers/firmware/efi/libstub/tpm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efi/libstub/tpm.c b/drivers/firmware/efi/libstub/tpm.c
index da661bf8cb96..13c1edd37e96 100644
--- a/drivers/firmware/efi/libstub/tpm.c
+++ b/drivers/firmware/efi/libstub/tpm.c
@@ -68,11 +68,11 @@ void efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t *sys_table_arg)
 	efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID;
 	efi_status_t status;
 	efi_physical_addr_t log_location, log_last_entry;
-	struct linux_efi_tpm_eventlog *log_tbl;
+	struct linux_efi_tpm_eventlog *log_tbl = NULL;
 	unsigned long first_entry_addr, last_entry_addr;
 	size_t log_size, last_entry_size;
 	efi_bool_t truncated;
-	void *tcg2_protocol;
+	void *tcg2_protocol = NULL;
 
 	status = efi_call_early(locate_protocol, &tcg2_guid, NULL,
 				&tcg2_protocol);