On 4/3/22 21:11, Tyler Fanelli wrote:
The length of the attestation report buffer is never checked to be
valid before allocation is made. If the length of the report is returned
to be 0, the buffer to retrieve the attestation buffer is allocated with
length 0 and passed to the kernel to fill with contents of the attestation
report. Leaving this unchecked is dangerous and could lead to undefined
behavior.
Signed-off-by: Tyler Fanelli <tfanelli@xxxxxxxxxx>
---
target/i386/sev.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/target/i386/sev.c b/target/i386/sev.c
index 025ff7a6f8..e82be3e350 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -616,6 +616,8 @@ static SevAttestationReport *sev_get_attestation_report(const char *mnonce,
return NULL;
}
+ input.len = 0;
I agree with Daniel's review of your v1:
"The declaration of 'input' already zero initializes."
https://lore.kernel.org/qemu-devel/YiJi9IYqtZvNQIRc@xxxxxxxxxx/
/* Query the report length */
ret = sev_ioctl(sev->sev_fd, KVM_SEV_GET_ATTESTATION_REPORT,
&input, &err);
@@ -626,6 +628,11 @@ static SevAttestationReport *sev_get_attestation_report(const char *mnonce,
ret, err, fw_error_to_str(err));
return NULL;
}
+ } else if (input.len == 0) {
+ error_setg(errp, "SEV: Failed to query attestation report:"
+ " length returned=%u",
+ input.len);
+ return NULL;
}
data = g_malloc(input.len);
