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Date: Fri, 10 Jun 2022 11:13:39 +0800 From: xiujianfeng <xiujianfeng@...wei.com> To: <zohar@...ux.ibm.com>, <dmitry.kasatkin@...il.com>, <jmorris@...ei.org>, <serge@...lyn.com> CC: <linux-integrity@...r.kernel.org>, <linux-security-module@...r.kernel.org>, <linux-kernel@...r.kernel.org> Subject: Re: [PATCH -next] Revert "evm: Fix memleak in init_desc" Hi, ping.... 在 2022/5/27 19:17, Xiu Jianfeng 写道: > This reverts commit ccf11dbaa07b328fa469415c362d33459c140a37. > > Commit ccf11dbaa07b ("evm: Fix memleak in init_desc") said there is > memleak in init_desc. That may be incorrect, as we can see, tmp_tfm is > saved in one of the two global variables hmac_tfm or evm_tfm[hash_algo], > then if init_desc is called next time, there is no need to alloc tfm > again, so in the error path of kmalloc desc or crypto_shash_init(desc), > It is not a problem without freeing tmp_tfm. > > And also that commit did not reset the global variable to NULL after > freeing tmp_tfm and this makes *tfm a dangling pointer which may cause a > UAF issue. > > Signed-off-by: Xiu Jianfeng <xiujianfeng@...wei.com> > --- > security/integrity/evm/evm_crypto.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c > index a733aff02006..708de9656bbd 100644 > --- a/security/integrity/evm/evm_crypto.c > +++ b/security/integrity/evm/evm_crypto.c > @@ -75,7 +75,7 @@ static struct shash_desc *init_desc(char type, uint8_t hash_algo) > { > long rc; > const char *algo; > - struct crypto_shash **tfm, *tmp_tfm = NULL; > + struct crypto_shash **tfm, *tmp_tfm; > struct shash_desc *desc; > > if (type == EVM_XATTR_HMAC) { > @@ -120,16 +120,13 @@ 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) { > - crypto_free_shash(tmp_tfm); > + if (!desc) > 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); > }
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