[PATCH] [v2] evm: Fix memleak in init_desc

[PATCH] [v2] evm: Fix memleak in init_desc

[Dinghao Liu]

When kmalloc() fails, tmp_tfm allocated by
crypto_alloc_shash() has not been freed, which
leads to memleak.

Fixes: d46eb3699502b ("evm: crypto hash replaced by shash")
Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
---

Changelog:

v2: - Remove checks against tmp_tfm before freeing.
---
 security/integrity/evm/evm_crypto.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index 168c3b78ac47..a6dd47eb086d 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -73,7 +73,7 @@ static struct shash_desc *init_desc(char type, uint8_t hash_algo)
 {
 	long rc;
 	const char *algo;
-	struct crypto_shash **tfm, *tmp_tfm;
+	struct crypto_shash **tfm, *tmp_tfm = NULL;
 	struct shash_desc *desc;
 
 	if (type == EVM_XATTR_HMAC) {
@@ -118,13 +118,16 @@ static struct shash_desc *init_desc(char type, uint8_t hash_algo)
 alloc:
 	desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
 			GFP_KERNEL);
-	if (!desc)
+	if (!desc) {
+		crypto_free_shash(tmp_tfm);
 		return ERR_PTR(-ENOMEM);
+	}
 
 	desc->tfm = *tfm;
 
 	rc = crypto_shash_init(desc);
 	if (rc) {
+		crypto_free_shash(tmp_tfm);
 		kfree(desc);
 		return ERR_PTR(rc);
 	}
-- 
2.17.1

Re: [PATCH v2] evm: Fix memory leak in init_desc

[Mimi Zohar]

Hi Dinghao,

On Sun, 2021-01-10 at 11:50 +0100, Markus Elfring wrote:
> > When kmalloc() fails, tmp_tfm allocated by
> > crypto_alloc_shash() has not been freed, which
> > leads to memleak.

In the future, please conform to Documentation/process/submitting-
patches.rst: 

  - The body of the explanation, line wrapped at 75 columns, which will
    be copied to the permanent changelog to describe this patch.

> 
> Do any Linux developers care for the following aspects?
> 
> * Imperative wordings for change descriptions
>   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?id=2ff90100ace886895e4fbb2850b8d5e49d931ed6#n89
> 
> * Usage of the term “memory leak” (instead of an abbreviation)

In general I agree, but this is a really small, obvious bug fix. 
Assuming Dinghao is fine with my updating the patch description, I'll
fix it.

Mimi

Re: [PATCH] [v2] evm: Fix memleak in init_desc

[Mimi Zohar]

Hi Dinghao,

On Sun, 2021-01-10 at 16:02 +0800, Dinghao Liu wrote:
> When kmalloc() fails, tmp_tfm allocated by
> crypto_alloc_shash() has not been freed, which
> leads to memleak.
> 
> Fixes: d46eb3699502b ("evm: crypto hash replaced by shash")
> Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>

This patch is now queued, with an updated patch description, in next-
integrity-testing.

thanks,

Mimi