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[v2,2/2] tcgbios: Only measure size indicated in UEFI partition table header

Message ID 20250405021507.2707113-3-stefanb@linux.ibm.com
State New
Headers show
Series tcgbios: Fix 2 issues related to handling of GPT table | expand

Commit Message

Stefan Berger April 5, 2025, 2:15 a.m. UTC 
Remove the reserved byte array from the UEFI_PARTITION_TABLE_HEADER
to avoid measuring zero bytes. Only log and measure the header as
indicated by its size. This size is expected to be exactly the size
of UEFI_PARTITION_TABLE_HEADER (= 92 bytes).

Fixes: 16a1867425ee ("tcgbios: Measure the GPT table")
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 lib/libtpm/tcgbios.c     | 12 ++++++++++--
 lib/libtpm/tcgbios_int.h |  1 -
 2 files changed, 10 insertions(+), 3 deletions(-)
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Patch

diff --git a/lib/libtpm/tcgbios.c b/lib/libtpm/tcgbios.c
index 5e657bd..30fd921 100644
--- a/lib/libtpm/tcgbios.c
+++ b/lib/libtpm/tcgbios.c
@@ -1080,6 +1080,8 @@  uint32_t tpm_measure_bcv_mbr(uint32_t bootdrv, const uint8_t *addr,
  */
 void tpm_gpt_set_lba1(const uint8_t *addr, uint32_t length)
 {
+	UEFI_PARTITION_TABLE_HEADER *upth = (UEFI_PARTITION_TABLE_HEADER *)addr;
+
 	if (!tpm_is_working())
 		return;
 
@@ -1090,8 +1092,14 @@  void tpm_gpt_set_lba1(const uint8_t *addr, uint32_t length)
 	if (!uefi_gpt_data)
 		return;
 
-	memcpy(&uefi_gpt_data->EfiPartitionHeader,
-	       addr, MIN(sizeof(uefi_gpt_data->EfiPartitionHeader), length));
+	/* Length must be at least the size of EfiPartitionHeader (92bytes) */
+	if (length < sizeof(uefi_gpt_data->EfiPartitionHeader) ||
+	    le32_to_cpu(upth->header.size) !=
+	      sizeof(uefi_gpt_data->EfiPartitionHeader))
+		return;
+
+	memcpy(&uefi_gpt_data->EfiPartitionHeader, addr,
+	       sizeof(uefi_gpt_data->EfiPartitionHeader));
 	uefi_gpt_data->NumberOfPartitions = cpu_to_le64(0);
 }
 
diff --git a/lib/libtpm/tcgbios_int.h b/lib/libtpm/tcgbios_int.h
index cc38455..5bbd9d5 100644
--- a/lib/libtpm/tcgbios_int.h
+++ b/lib/libtpm/tcgbios_int.h
@@ -116,7 +116,6 @@  typedef struct {
 	uint32_t numPartEntry;
 	uint32_t partEntrySize;
 	uint32_t partArrayCrc32;
-	uint8_t reserved[420];
 } __attribute__((packed)) UEFI_PARTITION_TABLE_HEADER;
 
 typedef struct {