KEYS: trusted: Fix memory leak in tpm2_key_encode()

On Tue, Dec 21, 2021 at 04:54:04PM +0800, Jianglei Nie wrote:

Line 36 (#1) allocates a memory chunk for scratch by kmalloc(), but
it is never freed through the function, which will lead to a memory
leak.

We should kfree() scratch before the function returns (#2, #3 and #4).

31 static int tpm2_key_encode(struct trusted_key_payload *payload,
32			   struct trusted_key_options *options,
33			   u8 *src, u32 len)
34 {
36	u8 *scratch = kmalloc(SCRATCH_SIZE, GFP_KERNEL);
      	// #1: kmalloc space
50	if (!scratch)
51		return -ENOMEM;

56	if (options->blobauth_len == 0) {
60		if (WARN(IS_ERR(w), "BUG: Boolean failed to encode"))
61			return PTR_ERR(w); // #2: missing kfree
63	}

71	if (WARN(work - scratch + pub_len + priv_len + 14 > SCRATCH_SIZE,
72		 "BUG: scratch buffer is too small"))
73		return -EINVAL; // #3: missing kfree

  	// #4: missing kfree: scratch is never used afterwards.
82	if (WARN(IS_ERR(work1), "BUG: ASN.1 encoder failed"))
83		return PTR_ERR(work1);

85	return work1 - payload->blob;
86 }

Signed-off-by: Jianglei Nie <redacted>

Please write a proper commit message and not just dump tool output. You
are completely lacking analysis of what the heck you are doing.

E.g. you could just:

"The internal buffer in tpm2_key_encode() is not freed, which leads to a
memory leak. Handle those cases with kfree()."

/Jarkko