[PATCH 1/6] tpm: fix signed/unsigned bug when checking event logs

Gregory Price
2024-09-06T20:28:21Z

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>
---
drivers/firmware/efi/tpm.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/firmware/efi/tpm.c b/drivers/firmware/efi/tpm.c
index e8d69bd548f3..9c3613e6af15 100644
--- 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));
--
2.43.0