Re: [PATCH][next] KEYS: trusted: Fix missing null return from kzalloc call

On 12/04/2021 17:48, James Bottomley wrote:

On Mon, 2021-04-12 at 17:01 +0100, Colin King wrote:

quoted

From: Colin Ian King <redacted>

The kzalloc call can return null with the GFP_KERNEL flag so
add a null check and exit via a new error exit label. Use the
same exit error label for another error path too.

Addresses-Coverity: ("Dereference null return value")
Fixes: 830027e2cb55 ("KEYS: trusted: Add generic trusted keys
framework")
Signed-off-by: Colin Ian King <redacted>
---
 security/keys/trusted-keys/trusted_core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_core.c

b/security/keys/trusted-keys/trusted_core.c
index ec3a066a4b42..90774793f0b1 100644

--- a/security/keys/trusted-keys/trusted_core.c
+++ b/security/keys/trusted-keys/trusted_core.c

@@ -116,11 +116,13 @@ static struct trusted_key_payload

*trusted_payload_alloc(struct key *key)
 
 	ret = key_payload_reserve(key, sizeof(*p));
 	if (ret < 0)
-		return p;
+		goto err;
 	p = kzalloc(sizeof(*p), GFP_KERNEL);
+	if (!p)
+		goto err;
 
 	p->migratable = migratable;
-
+err:
 	return p;

This is clearly a code migration bug in 

commit 251c85bd106099e6f388a89e88e12d14de2c9cda
Author: Sumit Garg [off-list ref]
Date:   Mon Mar 1 18:41:24 2021 +0530

    KEYS: trusted: Add generic trusted keys framework

Which has for addition to trusted_core.c:

+static struct trusted_key_payload *trusted_payload_alloc(struct key
*key)
+{
+       struct trusted_key_payload *p = NULL;
+       int ret;
+
+       ret = key_payload_reserve(key, sizeof(*p));
+       if (ret < 0)
+               return p;
+       p = kzalloc(sizeof(*p), GFP_KERNEL);
+
+       p->migratable = migratable;
+
+       return p;
+}

And for trusted_tpm1.c:

-static struct trusted_key_payload *trusted_payload_alloc(struct key
*key)
-{
-       struct trusted_key_payload *p = NULL;
-       int ret;
-
-       ret = key_payload_reserve(key, sizeof *p);
-       if (ret < 0)
-               return p;
-       p = kzalloc(sizeof *p, GFP_KERNEL);
-       if (p)
-               p->migratable = 1; /* migratable by default */
-       return p;
-}

The trusted_tpm1.c code was correct and we got this bug introduced by
what should have been a simple cut and paste ... how did that happen? 
And therefore, how safe is the rest of the extraction into
trusted_core.c?

fortunately it gets caught by static analysis, but it does make me also
concerned about what else has changed and how this gets through review.

James