tpm: fix signed/unsigned bug when checking event logs

[ Upstream commit e6d654e9f5a97742cfe794b1c4bb5d3fb2d25e98 ]

A prior bugfix that fixes a signed/unsigned error causes
another signed unsigned error.

A situation where log_tbl->size is invalid can cause the
size passed to memblock_reserve to become negative.

log_size from the main event log is an unsigned int, and
the code reduces to the following

u64 value = (int)unsigned_value;

This results in sign extension, and the value sent to
memblock_reserve becomes effectively negative.

Fixes: be59d57f9806 ("efi/tpm: Fix sanity check of unsigned tbl_size being less than zero")
Signed-off-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/firmware/efi/tpm.c b/drivers/firmware/efi/tpm.c
index e8d69bd548f3fe2a6f34eb9c3332f97076cd9722..9c3613e6af158f83bf58dab296ef093700c8246d 100644 (file)
--- a/drivers/firmware/efi/tpm.c
+++ b/drivers/firmware/efi/tpm.c
@@ -40,7 +40,8 @@ int __init efi_tpm_eventlog_init(void)
 {
        struct linux_efi_tpm_eventlog *log_tbl;
        struct efi_tcg2_final_events_table *final_tbl;
-       int tbl_size;
+       unsigned int tbl_size;
+       int final_tbl_size;
        int ret = 0;
 
        if (efi.tpm_log == EFI_INVALID_TABLE_ADDR) {
@@ -80,26 +81,26 @@ int __init efi_tpm_eventlog_init(void)
                goto out;
        }
 
-       tbl_size = 0;
+       final_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);
+               final_tbl_size = tpm2_calc_event_log_size(events,
+                                                         final_tbl->nr_events,
+                                                         log_tbl->log);
        }
 
-       if (tbl_size < 0) {
+       if (final_tbl_size < 0) {
                pr_err(FW_BUG "Failed to parse event in TPM Final Events Log\n");
                ret = -EINVAL;
                goto out_calc;
        }
 
        memblock_reserve(efi.tpm_final_log,
-                        tbl_size + sizeof(*final_tbl));
-       efi_tpm_final_log_size = tbl_size;
+                        final_tbl_size + sizeof(*final_tbl));
+       efi_tpm_final_log_size = final_tbl_size;
 
 out_calc:
        early_memunmap(final_tbl, sizeof(*final_tbl));