[PATCH v8 04/11] KEYS: trusted: Fix memory leak in tpm2_load()

[Jarkko Sakkinen]

tpm2_load() allocates a blob indirectly via tpm2_key_decode() but it is
not freed in all failure paths. Address this with a scope-based cleanup
helper __free(). For legacy blobs, the implicit de-allocation is gets
disable by no_free_ptr().

Cc: sta...@vger.kernel.org # v5.13+
Fixes: f2219745250f ("security: keys: trusted: use ASN.1 TPM2 key format for 
the blobs")
Signed-off-by: Jarkko Sakkinen <jar...@kernel.org>
---
v7:
- Fix compiler warning.
v6:
- A new patch in this version.
---
 security/keys/trusted-keys/trusted_tpm2.c | 24 +++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_tpm2.c 
b/security/keys/trusted-keys/trusted_tpm2.c
index edd7b9d7e4dc..36e20a9a94b4 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -98,9 +98,8 @@ struct tpm2_key_context {
        u32 priv_len;
 };
 
-static int tpm2_key_decode(struct trusted_key_payload *payload,
-                          struct trusted_key_options *options,
-                          u8 **buf)
+static void *tpm2_key_decode(struct trusted_key_payload *payload,
+                            struct trusted_key_options *options)
 {
        int ret;
        struct tpm2_key_context ctx;
@@ -111,16 +110,15 @@ static int tpm2_key_decode(struct trusted_key_payload 
*payload,
        ret = asn1_ber_decoder(&tpm2key_decoder, &ctx, payload->blob,
                               payload->blob_len);
        if (ret < 0)
-               return ret;
+               return ERR_PTR(ret);
 
        if (ctx.priv_len + ctx.pub_len > MAX_BLOB_SIZE)
-               return -EINVAL;
+               return ERR_PTR(-EINVAL);
 
        blob = kmalloc(ctx.priv_len + ctx.pub_len + 4, GFP_KERNEL);
        if (!blob)
-               return -ENOMEM;
+               return ERR_PTR(-ENOMEM);
 
-       *buf = blob;
        options->keyhandle = ctx.parent;
 
        memcpy(blob, ctx.priv, ctx.priv_len);
@@ -128,7 +126,7 @@ static int tpm2_key_decode(struct trusted_key_payload 
*payload,
 
        memcpy(blob, ctx.pub, ctx.pub_len);
 
-       return 0;
+       return blob;
 }
 
 int tpm2_key_parent(void *context, size_t hdrlen,
@@ -372,6 +370,7 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
                         struct trusted_key_options *options,
                         u32 *blob_handle)
 {
+       u8 *blob_ref __free(kfree) = NULL;
        struct tpm_buf buf;
        unsigned int private_len;
        unsigned int public_len;
@@ -380,11 +379,14 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
        int rc;
        u32 attrs;
 
-       rc = tpm2_key_decode(payload, options, &blob);
-       if (rc) {
+       blob = tpm2_key_decode(payload, options);
+       if (IS_ERR(blob)) {
                /* old form */
                blob = payload->blob;
                payload->old_format = 1;
+       } else {
+               /* Bind to cleanup: */
+               blob_ref = blob;
        }
 
        /* new format carries keyhandle but old format doesn't */
@@ -449,8 +451,6 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
                        (__be32 *) &buf.data[TPM_HEADER_SIZE]);
 
 out:
-       if (blob != payload->blob)
-               kfree(blob);
        tpm_buf_destroy(&buf);
 
        if (rc > 0)
-- 
2.52.0