Commit dd093fb0 authored by Tom Lendacky's avatar Tom Lendacky Committed by Borislav Petkov (AMD)
Browse files

virt/sev-guest: Return -EIO if certificate buffer is not large enough 



Commit

  47894e0f ("virt/sev-guest: Prevent IV reuse in the SNP guest driver")

changed the behavior associated with the return value when the caller
does not supply a large enough certificate buffer. Prior to the commit a
value of -EIO was returned. Now, 0 is returned.  This breaks the
established ABI with the user.

Change the code to detect the buffer size error and return -EIO.

Fixes: 47894e0f ("virt/sev-guest: Prevent IV reuse in the SNP guest driver")
Reported-by: default avatarLarry Dewey <larry.dewey@amd.com>
Signed-off-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Tested-by: default avatarLarry Dewey <larry.dewey@amd.com>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/r/2afbcae6daf13f7ad5a4296692e0a0fe1bc1e4ee.1677083979.git.thomas.lendacky@amd.com
parent e02b50ca

drivers/virt/coco/sev-guest/sev-guest.c

+17 −3
Original line number Diff line number Diff line
@@ -377,9 +377,26 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in 
		snp_dev->input.data_npages = certs_npages;

	}



	/*

	 * Increment the message sequence number. There is no harm in doing

	 * this now because decryption uses the value stored in the response

	 * structure and any failure will wipe the VMPCK, preventing further

	 * use anyway.

	 */

	snp_inc_msg_seqno(snp_dev);



	if (fw_err)

		*fw_err = err;



	/*

	 * If an extended guest request was issued and the supplied certificate

	 * buffer was not large enough, a standard guest request was issued to

	 * prevent IV reuse. If the standard request was successful, return -EIO

	 * back to the caller as would have originally been returned.

	 */

	if (!rc && err == SNP_GUEST_REQ_INVALID_LEN)

		return -EIO;



	if (rc) {

		dev_alert(snp_dev->dev,

			  "Detected error from ASP request. rc: %d, fw_err: %llu\n",
@@ -395,9 +412,6 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in 
		goto disable_vmpck;

	}



	/* Increment to new message sequence after payload decryption was successful. */

	snp_inc_msg_seqno(snp_dev);



	return 0;



disable_vmpck: