The loopback image is configured to function as a disk by being mapped
as a block device. Instead of measuring the entire block device, we
should focus on tracking the individual files accessed from it. For
example, we do not directly measure block devices like disk hd0, but the
files opened from it.
This method is important to avoid running out of memory, since loopback
images can be very large. Trying to read and measure the whole image at
once could cause out of memory errors and disrupt the boot process.
Signed-Off-by: Michael Chang <mch...@suse.com>
---
grub-core/commands/tpm.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/grub-core/commands/tpm.c b/grub-core/commands/tpm.c
index 324423ef8..2350d660d 100644
--- a/grub-core/commands/tpm.c
+++ b/grub-core/commands/tpm.c
@@ -36,6 +36,16 @@ grub_tpm_verify_init (grub_file_t io,
{
*context = io->name;
*flags |= GRUB_VERIFY_FLAGS_SINGLE_CHUNK;
+
+ /*
+ * The loopback image is mapped as a disk, allowing it to function like a
+ * block device. However, we measure the files read from the block device,
+ * not the device itself. For example, we don't measure block devices like
+ * disk hd0 directly. This process is crucial to prevent out-of-memory
+ * errors, as loopback images are inherently large.
+ */
+ if ((type & GRUB_FILE_TYPE_MASK) == GRUB_FILE_TYPE_LOOPBACK)
+ *flags = GRUB_VERIFY_FLAGS_SKIP_VERIFICATION;
return GRUB_ERR_NONE;
}
--
2.46.1
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