LinuxLists.cc - [PATCH] security:trusted_tpm2: Fix memory leak in tpm2_key

2021-12-12 13:56:17

Subject: [PATCH] security:trusted_tpm2: Fix memory leak in tpm2_key_encode()

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
37 u8 *work = scratch, *work1;
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 <[email protected]>
---
security/keys/trusted-keys/trusted_tpm2.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 0165da386289..3408a74c855f 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);
}

@@ -69,9 +71,12 @@ 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;
+ }

+ kfree(scratch);
work = asn1_encode_integer(work, end_work, options->keyhandle);
work = asn1_encode_octet_string(work, end_work, pub, pub_len);
work = asn1_encode_octet_string(work, end_work, priv, priv_len);
--
2.25.1

2021-12-12 21:21:35

by Serge E. Hallyn

[permalink] [raw]

Subject: Re: [PATCH] security:trusted_tpm2: Fix memory leak in tpm2_key_encode()

On Sun, Dec 12, 2021 at 09:54:03PM +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
> 37 u8 *work = scratch, *work1;
> 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 <[email protected]>

I don't know that we need to keep the line by line recap in
the full git log, but it def looks correct:

Reviewed-by: Serge Hallyn <[email protected]>

thanks,
-serge

> ---
> security/keys/trusted-keys/trusted_tpm2.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
> index 0165da386289..3408a74c855f 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);
> }
>
> @@ -69,9 +71,12 @@ 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;
> + }
>
> + kfree(scratch);
> work = asn1_encode_integer(work, end_work, options->keyhandle);
> work = asn1_encode_octet_string(work, end_work, pub, pub_len);
> work = asn1_encode_octet_string(work, end_work, priv, priv_len);
> --
> 2.25.1

2021-12-21 08:33:07

by Jarkko Sakkinen

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