diff mbox series

security:trusted_tpm2: Fix memory leak in tpm2_key_encode()

Message ID 20211221085404.6769-1-niejianglei2021@163.com (mailing list archive)
State New, archived
Headers show
Series security:trusted_tpm2: Fix memory leak in tpm2_key_encode() | expand

Commit Message

Jianglei Nie Dec. 21, 2021, 8:54 a.m. UTC
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 <niejianglei2021@163.com>
---
 security/keys/trusted-keys/trusted_tpm2.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

Comments

Jarkko Sakkinen Dec. 29, 2021, 12:08 a.m. UTC | #1
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 <niejianglei2021@163.com>

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
diff mbox series

Patch

diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 0165da386289..7bb1119b1dea 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -57,8 +57,10 @@  static int tpm2_key_encode(struct trusted_key_payload *payload,
 		unsigned char bool[3], *w = bool;
 		/* tag 0 is emptyAuth */
 		w = asn1_encode_boolean(w, w + sizeof(bool), true);
-		if (WARN(IS_ERR(w), "BUG: Boolean failed to encode"))
+		if (WARN(IS_ERR(w), "BUG: Boolean failed to encode")) {
+			kfree(scratch);
 			return PTR_ERR(w);
+		}
 		work = asn1_encode_tag(work, end_work, 0, bool, w - bool);
 	}
 
@@ -69,8 +71,10 @@  static int tpm2_key_encode(struct trusted_key_payload *payload,
 	 * trigger, so if it does there's something nefarious going on
 	 */
 	if (WARN(work - scratch + pub_len + priv_len + 14 > SCRATCH_SIZE,
-		 "BUG: scratch buffer is too small"))
+		 "BUG: scratch buffer is too small")) {
+		kfree(scratch);
 		return -EINVAL;
+	}
 
 	work = asn1_encode_integer(work, end_work, options->keyhandle);
 	work = asn1_encode_octet_string(work, end_work, pub, pub_len);
@@ -79,6 +83,7 @@  static int tpm2_key_encode(struct trusted_key_payload *payload,
 	work1 = payload->blob;
 	work1 = asn1_encode_sequence(work1, work1 + sizeof(payload->blob),
 				     scratch, work - scratch);
+	kfree(scratch);
 	if (WARN(IS_ERR(work1), "BUG: ASN.1 encoder failed"))
 		return PTR_ERR(work1);