On Fri, Jul 23, 2021 at 06:21:21PM +0100, Colin King wrote:
> @@ -441,6 +449,10 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
> rc = -EPERM;
>
> return rc;
> +
> +err:
> + kfree(blob);
This needs to be:
if (blob != payload->blob)
kfree(blob);
Otherwise it leads to a use after free.
> + return rc;
> }
How this is allocated is pretty scary looking!
security/keys/trusted-keys/trusted_tpm2.c
96 static int tpm2_key_decode(struct trusted_key_payload *payload,
97 struct trusted_key_options *options,
98 u8 **buf)
99 {
100 int ret;
101 struct tpm2_key_context ctx;
102 u8 *blob;
103
104 memset(&ctx, 0, sizeof(ctx));
105
106 ret = asn1_ber_decoder(&tpm2key_decoder, &ctx, payload->blob,
107 payload->blob_len);
108 if (ret < 0)
109 return ret;
Old form?
110
111 if (ctx.priv_len + ctx.pub_len > MAX_BLOB_SIZE)
112 return -EINVAL;
It's really scary to me that if the lengths are too large for kmalloc()
then we just use "payload->blob".
113
114 blob = kmalloc(ctx.priv_len + ctx.pub_len + 4, GFP_KERNEL);
blob is allocated here.
115 if (!blob)
116 return -ENOMEM;
117
118 *buf = blob;
119 options->keyhandle = ctx.parent;
120
121 memcpy(blob, ctx.priv, ctx.priv_len);
122 blob += ctx.priv_len;
123
124 memcpy(blob, ctx.pub, ctx.pub_len);
125
126 return 0;
127 }
[ snip ]
371 u32 attrs;
372
373 rc = tpm2_key_decode(payload, options, &blob);
374 if (rc) {
375 /* old form */
376 blob = payload->blob;
^^^^^^^^^^^^^^^^^^^^
377 payload->old_format = 1;
378 }
379
regards,
dan carpenter
