Messages in this thread |  | | Date | Mon, 26 Jul 2021 11:50:51 +0300 | From | Dan Carpenter <> | Subject | Re: [PATCH] security: keys: trusted: Fix memory leaks on allocated blob |
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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
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