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Date: Sat, 9 Jan 2021 22:53:38 -0800 From: Eric Biggers <ebiggers@...nel.org> To: dinghao.liu@....edu.cn Cc: kjlu@....edu, Mimi Zohar <zohar@...ux.ibm.com>, James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>, Dmitry Kasatkin <dmitry.kasatkin@...ia.com>, linux-integrity@...r.kernel.org, linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: Re: [PATCH] evm: Fix memleak in init_desc On Sun, Jan 10, 2021 at 01:27:09PM +0800, dinghao.liu@....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@....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
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