diff mbox series

evm: Fix memleak in init_desc

Message ID 20210109113305.11035-1-dinghao.liu@zju.edu.cn (mailing list archive)
State New
Headers show
Series evm: Fix memleak in init_desc | expand

Commit Message

Dinghao Liu Jan. 9, 2021, 11:33 a.m. UTC
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>
---
 security/integrity/evm/evm_crypto.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

Comments

Eric Biggers Jan. 9, 2021, 5:07 p.m. UTC | #1
On Sat, Jan 09, 2021 at 07:33:05PM +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>
> ---
>  security/integrity/evm/evm_crypto.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
> index 168c3b78ac47..39fb31a638ac 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 +118,18 @@ 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) {
> +		if (tmp_tfm)
> +			crypto_free_shash(tmp_tfm);
>  		return ERR_PTR(-ENOMEM);
> +	}
>  
>  	desc->tfm = *tfm;
>  
>  	rc = crypto_shash_init(desc);
>  	if (rc) {
> +		if (tmp_tfm)
> +			crypto_free_shash(tmp_tfm);
>  		kfree(desc);
>  		return ERR_PTR(rc);
>  	}

There's no need to check for NULL before calling crypto_free_shash().

- Eric
Dinghao Liu Jan. 10, 2021, 5:27 a.m. UTC | #2
> On Sat, Jan 09, 2021 at 07:33:05PM +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>
> > ---
> >  security/integrity/evm/evm_crypto.c | 9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> > 
> > diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
> > index 168c3b78ac47..39fb31a638ac 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 +118,18 @@ 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) {
> > +		if (tmp_tfm)
> > +			crypto_free_shash(tmp_tfm);
> >  		return ERR_PTR(-ENOMEM);
> > +	}
> >  
> >  	desc->tfm = *tfm;
> >  
> >  	rc = crypto_shash_init(desc);
> >  	if (rc) {
> > +		if (tmp_tfm)
> > +			crypto_free_shash(tmp_tfm);
> >  		kfree(desc);
> >  		return ERR_PTR(rc);
> >  	}
> 
> There's no need to check for NULL before calling crypto_free_shash().
> 

I find there is a crypto_shash_tfm() in the definition of 
crypto_free_shash(). Will this lead to null pointer dereference
when we use it to free a NULL pointer?

Regards,
Dinghao
Eric Biggers Jan. 10, 2021, 6:53 a.m. UTC | #3
On Sun, Jan 10, 2021 at 01:27:09PM +0800, dinghao.liu@zju.edu.cn wrote:
> > On Sat, Jan 09, 2021 at 07:33:05PM +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>
> > > ---
> > >  security/integrity/evm/evm_crypto.c | 9 +++++++--
> > >  1 file changed, 7 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
> > > index 168c3b78ac47..39fb31a638ac 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 +118,18 @@ 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) {
> > > +		if (tmp_tfm)
> > > +			crypto_free_shash(tmp_tfm);
> > >  		return ERR_PTR(-ENOMEM);
> > > +	}
> > >  
> > >  	desc->tfm = *tfm;
> > >  
> > >  	rc = crypto_shash_init(desc);
> > >  	if (rc) {
> > > +		if (tmp_tfm)
> > > +			crypto_free_shash(tmp_tfm);
> > >  		kfree(desc);
> > >  		return ERR_PTR(rc);
> > >  	}
> > 
> > There's no need to check for NULL before calling crypto_free_shash().
> > 
> 
> I find there is a crypto_shash_tfm() in the definition of 
> crypto_free_shash(). Will this lead to null pointer dereference
> when we use it to free a NULL pointer?
> 

No.  It does &tfm->base, not tfm->base.

- Eric
Dinghao Liu Jan. 10, 2021, 7:01 a.m. UTC | #4
> On Sun, Jan 10, 2021 at 01:27:09PM +0800, dinghao.liu@zju.edu.cn wrote:
> > > On Sat, Jan 09, 2021 at 07:33:05PM +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>
> > > > ---
> > > >  security/integrity/evm/evm_crypto.c | 9 +++++++--
> > > >  1 file changed, 7 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
> > > > index 168c3b78ac47..39fb31a638ac 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 +118,18 @@ 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) {
> > > > +		if (tmp_tfm)
> > > > +			crypto_free_shash(tmp_tfm);
> > > >  		return ERR_PTR(-ENOMEM);
> > > > +	}
> > > >  
> > > >  	desc->tfm = *tfm;
> > > >  
> > > >  	rc = crypto_shash_init(desc);
> > > >  	if (rc) {
> > > > +		if (tmp_tfm)
> > > > +			crypto_free_shash(tmp_tfm);
> > > >  		kfree(desc);
> > > >  		return ERR_PTR(rc);
> > > >  	}
> > > 
> > > There's no need to check for NULL before calling crypto_free_shash().
> > > 
> > 
> > I find there is a crypto_shash_tfm() in the definition of 
> > crypto_free_shash(). Will this lead to null pointer dereference
> > when we use it to free a NULL pointer?
> > 
> 
> No.  It does &tfm->base, not tfm->base.
> 

Thank you for your advice! I will resend a new patch soon.

Regards,
Dinghao
diff mbox series

Patch

diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index 168c3b78ac47..39fb31a638ac 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 +118,18 @@  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) {
+		if (tmp_tfm)
+			crypto_free_shash(tmp_tfm);
 		return ERR_PTR(-ENOMEM);
+	}
 
 	desc->tfm = *tfm;
 
 	rc = crypto_shash_init(desc);
 	if (rc) {
+		if (tmp_tfm)
+			crypto_free_shash(tmp_tfm);
 		kfree(desc);
 		return ERR_PTR(rc);
 	}