linux-kernel - [PATCH 2/2] crypto: ccp - Fail the PSP initialization when writing psp data file failed

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Message-Id: <20220802185534.735338-3-jackyli@google.com>
Date:   Tue,  2 Aug 2022 18:55:34 +0000
From:   Jacky Li <jackyli@...gle.com>
To:     Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        John Allen <john.allen@....com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Marc Orr <marcorr@...gle.com>, Alper Gun <alpergun@...gle.com>,
        Peter Gonda <pgonda@...gle.com>, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jacky Li <jackyli@...gle.com>
Subject: [PATCH 2/2] crypto: ccp - Fail the PSP initialization when writing
 psp data file failed

Currently the OS continues the PSP initialization when there is a write
failure to the init_ex_file. Therefore, the userspace would be told that
SEV is properly INIT'd even though the psp data file is not updated.
This is problematic because later when asked for the SEV data, the OS
won't be able to provide it.

Fixes: 3d725965f836 ("crypto: ccp - Add SEV_INIT_EX support")
Reported-by: Peter Gonda <pgonda@...gle.com>
Signed-off-by: Jacky Li <jackyli@...gle.com>
---
 drivers/crypto/ccp/sev-dev.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 5bb2ae250d38..fd6bb01eb198 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -233,7 +233,7 @@ static int sev_read_init_ex_file(void)
 	return 0;
 }
 
-static void sev_write_init_ex_file(void)
+static int sev_write_init_ex_file(void)
 {
 	struct sev_device *sev = psp_master->sev_data;
 	struct file *fp;
@@ -243,14 +243,15 @@ static void sev_write_init_ex_file(void)
 	lockdep_assert_held(&sev_cmd_mutex);
 
 	if (!sev_init_ex_buffer)
-		return;
+		return 0;
 
 	fp = open_file_as_root(init_ex_path, O_CREAT | O_WRONLY, 0600);
 	if (IS_ERR(fp)) {
+		int ret = PTR_ERR(fp);
 		dev_err(sev->dev,
 			"SEV: could not open file for write, error %ld\n",
-			PTR_ERR(fp));
-		return;
+			ret);
+		return ret;
 	}
 
 	nwrite = kernel_write(fp, sev_init_ex_buffer, NV_LENGTH, &offset);
@@ -261,18 +262,20 @@ static void sev_write_init_ex_file(void)
 		dev_err(sev->dev,
 			"SEV: failed to write %u bytes to non volatile memory area, ret %ld\n",
 			NV_LENGTH, nwrite);
-		return;
+		return -EIO;
 	}
 
 	dev_dbg(sev->dev, "SEV: write successful to NV file\n");
+
+	return 0;
 }
 
-static void sev_write_init_ex_file_if_required(int cmd_id)
+static int sev_write_init_ex_file_if_required(int cmd_id)
 {
 	lockdep_assert_held(&sev_cmd_mutex);
 
 	if (!sev_init_ex_buffer)
-		return;
+		return 0;
 
 	/*
 	 * Only a few platform commands modify the SPI/NV area, but none of the
@@ -287,10 +290,10 @@ static void sev_write_init_ex_file_if_required(int cmd_id)
 	case SEV_CMD_PEK_GEN:
 		break;
 	default:
-		return;
+		return 0;
 	}
 
-	sev_write_init_ex_file();
+	return sev_write_init_ex_file();
 }
 
 static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
@@ -363,7 +366,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
 			cmd, reg & PSP_CMDRESP_ERR_MASK);
 		ret = -EIO;
 	} else {
-		sev_write_init_ex_file_if_required(cmd);
+		ret = sev_write_init_ex_file_if_required(cmd);
 	}
 
 	print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data,
-- 
2.37.1.455.g008518b4e5-goog