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From: Roberto Sassu <roberto.sassu@huaweicloud.com>
To: zohar@linux.ibm.com, dmitry.kasatkin@gmail.com,
paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com
Cc: linux-integrity@vger.kernel.org,
linux-security-module@vger.kernel.org,
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Roberto Sassu <roberto.sassu@huawei.com>,
stable@vger.kernel.org
Subject: [PATCH v2 1/2] evm: Alloc evm_digest in evm_verify_hmac() if
CONFIG_VMAP_STACK=y
Date: Thu, 1 Dec 2022 11:06:24 +0100
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| Series |
ima/evm: Ensure digest to verify is in linear mapping area
|
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Commit Message
Roberto Sassu
Dec. 1, 2022, 10:06 a.m. UTC
From: Roberto Sassu <roberto.sassu@huawei.com> Commit ac4e97abce9b8 ("scatterlist: sg_set_buf() argument must be in linear mapping") checks that both the signature and the digest reside in the linear mapping area. However, more recently commit ba14a194a434c ("fork: Add generic vmalloced stack support"), made it possible to move the stack in the vmalloc area, which is not contiguous, and thus not suitable for sg_set_buf() which needs adjacent pages. Fix this by checking if CONFIG_VMAP_STACK is enabled. If yes, allocate an evm_digest structure, and use that instead of the in-stack counterpart. Cc: stable@vger.kernel.org # 4.9.x Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support") Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> --- security/integrity/evm/evm_main.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-)
Comments
On Thu, Dec 01, 2022 at 11:06:24AM +0100, Roberto Sassu wrote: > From: Roberto Sassu <roberto.sassu@huawei.com> > > Commit ac4e97abce9b8 ("scatterlist: sg_set_buf() argument must be in linear > mapping") checks that both the signature and the digest reside in the > linear mapping area. > > However, more recently commit ba14a194a434c ("fork: Add generic vmalloced > stack support"), made it possible to move the stack in the vmalloc area, > which is not contiguous, and thus not suitable for sg_set_buf() which needs > adjacent pages. > > Fix this by checking if CONFIG_VMAP_STACK is enabled. If yes, allocate an > evm_digest structure, and use that instead of the in-stack counterpart. > > Cc: stable@vger.kernel.org # 4.9.x > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support") > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > --- > security/integrity/evm/evm_main.c | 26 +++++++++++++++++++++----- > 1 file changed, 21 insertions(+), 5 deletions(-) > > diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c > index 23d484e05e6f..7f76d6103f2e 100644 > --- a/security/integrity/evm/evm_main.c > +++ b/security/integrity/evm/evm_main.c > @@ -174,6 +174,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > struct signature_v2_hdr *hdr; > enum integrity_status evm_status = INTEGRITY_PASS; > struct evm_digest digest; > + struct evm_digest *digest_ptr = &digest; > struct inode *inode; > int rc, xattr_len, evm_immutable = 0; > > @@ -231,14 +232,26 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > } > > hdr = (struct signature_v2_hdr *)xattr_data; > - digest.hdr.algo = hdr->hash_algo; > + > + if (IS_ENABLED(CONFIG_VMAP_STACK)) { > + digest_ptr = kmalloc(sizeof(*digest_ptr), GFP_NOFS); > + if (!digest_ptr) { > + rc = -ENOMEM; > + break; > + } > + } > + > + digest_ptr->hdr.algo = hdr->hash_algo; > + > rc = evm_calc_hash(dentry, xattr_name, xattr_value, > - xattr_value_len, xattr_data->type, &digest); > + xattr_value_len, xattr_data->type, > + digest_ptr); > if (rc) > break; > rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM, > (const char *)xattr_data, xattr_len, > - digest.digest, digest.hdr.length); > + digest_ptr->digest, > + digest_ptr->hdr.length); > if (!rc) { > inode = d_backing_inode(dentry); > > @@ -268,8 +281,11 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > else > evm_status = INTEGRITY_FAIL; > } > - pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length, > - digest.digest); > + pr_debug("digest: (%d) [%*phN]\n", digest_ptr->hdr.length, > + digest_ptr->hdr.length, digest_ptr->digest); > + > + if (digest_ptr && digest_ptr != &digest) > + kfree(digest_ptr); What is the actual problem here? Where is a scatterlist being created from this buffer? AFAICS it never happens. - Eric
On Thu, 2022-12-01 at 10:53 -0800, Eric Biggers wrote: > On Thu, Dec 01, 2022 at 11:06:24AM +0100, Roberto Sassu wrote: > > From: Roberto Sassu <roberto.sassu@huawei.com> > > > > Commit ac4e97abce9b8 ("scatterlist: sg_set_buf() argument must be in linear > > mapping") checks that both the signature and the digest reside in the > > linear mapping area. > > > > However, more recently commit ba14a194a434c ("fork: Add generic vmalloced > > stack support"), made it possible to move the stack in the vmalloc area, > > which is not contiguous, and thus not suitable for sg_set_buf() which needs > > adjacent pages. > > > > Fix this by checking if CONFIG_VMAP_STACK is enabled. If yes, allocate an > > evm_digest structure, and use that instead of the in-stack cbounterpart. > > > > Cc: stable@vger.kernel.org # 4.9.x > > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support") > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > > --- > > security/integrity/evm/evm_main.c | 26 +++++++++++++++++++++----- > > 1 file changed, 21 insertions(+), 5 deletions(-) > > > > diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c > > index 23d484e05e6f..7f76d6103f2e 100644 > > --- a/security/integrity/evm/evm_main.c > > +++ b/security/integrity/evm/evm_main.c > > @@ -174,6 +174,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > struct signature_v2_hdr *hdr; > > enum integrity_status evm_status = INTEGRITY_PASS; > > struct evm_digest digest; > > + struct evm_digest *digest_ptr = &digest; > > struct inode *inode; > > int rc, xattr_len, evm_immutable = 0; > > > > @@ -231,14 +232,26 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > } > > > > hdr = (struct signature_v2_hdr *)xattr_data; > > - digest.hdr.algo = hdr->hash_algo; > > + > > + if (IS_ENABLED(CONFIG_VMAP_STACK)) { > > + digest_ptr = kmalloc(sizeof(*digest_ptr), GFP_NOFS); > > + if (!digest_ptr) { > > + rc = -ENOMEM; > > + break; > > + } > > + } > > + > > + digest_ptr->hdr.algo = hdr->hash_algo; > > + > > rc = evm_calc_hash(dentry, xattr_name, xattr_value, > > - xattr_value_len, xattr_data->type, &digest); > > + xattr_value_len, xattr_data->type, > > + digest_ptr); > > if (rc) > > break; > > rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM, > > (const char *)xattr_data, xattr_len, > > - digest.digest, digest.hdr.length); > > + digest_ptr->digest, > > + digest_ptr->hdr.length); > > if (!rc) { > > inode = d_backing_inode(dentry); > > > > @@ -268,8 +281,11 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > else > > evm_status = INTEGRITY_FAIL; > > } > > - pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length, > > - digest.digest); > > + pr_debug("digest: (%d) [%*phN]\n", digest_ptr->hdr.length, > > + digest_ptr->hdr.length, digest_ptr->digest); > > + > > + if (digest_ptr && digest_ptr != &digest) > > + kfree(digest_ptr); > > What is the actual problem here? Where is a scatterlist being created from this > buffer? AFAICS it never happens. Enabling CONFIG_VMAP_STACK is the culprit, which triggers the BUG_ON only when CONFIG_DEBUG_SG is enabled as well. Refer to commit ba14a194a434 ("fork: Add generic vmalloced stack support").
On Thu, Dec 01, 2022 at 02:08:58PM -0500, Mimi Zohar wrote: > On Thu, 2022-12-01 at 10:53 -0800, Eric Biggers wrote: > > On Thu, Dec 01, 2022 at 11:06:24AM +0100, Roberto Sassu wrote: > > > From: Roberto Sassu <roberto.sassu@huawei.com> > > > > > > Commit ac4e97abce9b8 ("scatterlist: sg_set_buf() argument must be in linear > > > mapping") checks that both the signature and the digest reside in the > > > linear mapping area. > > > > > > However, more recently commit ba14a194a434c ("fork: Add generic vmalloced > > > stack support"), made it possible to move the stack in the vmalloc area, > > > which is not contiguous, and thus not suitable for sg_set_buf() which needs > > > adjacent pages. > > > > > > Fix this by checking if CONFIG_VMAP_STACK is enabled. If yes, allocate an > > > evm_digest structure, and use that instead of the in-stack cbounterpart. > > > > > > Cc: stable@vger.kernel.org # 4.9.x > > > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support") > > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > > > --- > > > security/integrity/evm/evm_main.c | 26 +++++++++++++++++++++----- > > > 1 file changed, 21 insertions(+), 5 deletions(-) > > > > > > diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c > > > index 23d484e05e6f..7f76d6103f2e 100644 > > > --- a/security/integrity/evm/evm_main.c > > > +++ b/security/integrity/evm/evm_main.c > > > @@ -174,6 +174,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > struct signature_v2_hdr *hdr; > > > enum integrity_status evm_status = INTEGRITY_PASS; > > > struct evm_digest digest; > > > + struct evm_digest *digest_ptr = &digest; > > > struct inode *inode; > > > int rc, xattr_len, evm_immutable = 0; > > > > > > @@ -231,14 +232,26 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > } > > > > > > hdr = (struct signature_v2_hdr *)xattr_data; > > > - digest.hdr.algo = hdr->hash_algo; > > > + > > > + if (IS_ENABLED(CONFIG_VMAP_STACK)) { > > > + digest_ptr = kmalloc(sizeof(*digest_ptr), GFP_NOFS); > > > + if (!digest_ptr) { > > > + rc = -ENOMEM; > > > + break; > > > + } > > > + } > > > + > > > + digest_ptr->hdr.algo = hdr->hash_algo; > > > + > > > rc = evm_calc_hash(dentry, xattr_name, xattr_value, > > > - xattr_value_len, xattr_data->type, &digest); > > > + xattr_value_len, xattr_data->type, > > > + digest_ptr); > > > if (rc) > > > break; > > > rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM, > > > (const char *)xattr_data, xattr_len, > > > - digest.digest, digest.hdr.length); > > > + digest_ptr->digest, > > > + digest_ptr->hdr.length); > > > if (!rc) { > > > inode = d_backing_inode(dentry); > > > > > > @@ -268,8 +281,11 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > else > > > evm_status = INTEGRITY_FAIL; > > > } > > > - pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length, > > > - digest.digest); > > > + pr_debug("digest: (%d) [%*phN]\n", digest_ptr->hdr.length, > > > + digest_ptr->hdr.length, digest_ptr->digest); > > > + > > > + if (digest_ptr && digest_ptr != &digest) > > > + kfree(digest_ptr); > > > > What is the actual problem here? Where is a scatterlist being created from this > > buffer? AFAICS it never happens. > > Enabling CONFIG_VMAP_STACK is the culprit, which triggers the BUG_ON > only when CONFIG_DEBUG_SG is enabled as well. > > Refer to commit ba14a194a434 ("fork: Add generic vmalloced stack > support"). I'm asking about where the actual bug is. Where is a scatterlist being created to represent an on-disk buffer... - Eric
On Thu, 2022-12-01 at 10:53 -0800, Eric Biggers wrote: > On Thu, Dec 01, 2022 at 11:06:24AM +0100, Roberto Sassu wrote: > > From: Roberto Sassu <roberto.sassu@huawei.com> > > > > Commit ac4e97abce9b8 ("scatterlist: sg_set_buf() argument must be in linear > > mapping") checks that both the signature and the digest reside in the > > linear mapping area. > > > > However, more recently commit ba14a194a434c ("fork: Add generic vmalloced > > stack support"), made it possible to move the stack in the vmalloc area, > > which is not contiguous, and thus not suitable for sg_set_buf() which needs > > adjacent pages. > > > > Fix this by checking if CONFIG_VMAP_STACK is enabled. If yes, allocate an > > evm_digest structure, and use that instead of the in-stack counterpart. > > > > Cc: stable@vger.kernel.org # 4.9.x > > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support") > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > > --- > > security/integrity/evm/evm_main.c | 26 +++++++++++++++++++++----- > > 1 file changed, 21 insertions(+), 5 deletions(-) > > > > diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c > > index 23d484e05e6f..7f76d6103f2e 100644 > > --- a/security/integrity/evm/evm_main.c > > +++ b/security/integrity/evm/evm_main.c > > @@ -174,6 +174,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > struct signature_v2_hdr *hdr; > > enum integrity_status evm_status = INTEGRITY_PASS; > > struct evm_digest digest; > > + struct evm_digest *digest_ptr = &digest; > > struct inode *inode; > > int rc, xattr_len, evm_immutable = 0; > > > > @@ -231,14 +232,26 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > } > > > > hdr = (struct signature_v2_hdr *)xattr_data; > > - digest.hdr.algo = hdr->hash_algo; > > + > > + if (IS_ENABLED(CONFIG_VMAP_STACK)) { > > + digest_ptr = kmalloc(sizeof(*digest_ptr), GFP_NOFS); > > + if (!digest_ptr) { > > + rc = -ENOMEM; > > + break; > > + } > > + } > > + > > + digest_ptr->hdr.algo = hdr->hash_algo; > > + > > rc = evm_calc_hash(dentry, xattr_name, xattr_value, > > - xattr_value_len, xattr_data->type, &digest); > > + xattr_value_len, xattr_data->type, > > + digest_ptr); > > if (rc) > > break; > > rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM, > > (const char *)xattr_data, xattr_len, > > - digest.digest, digest.hdr.length); > > + digest_ptr->digest, > > + digest_ptr->hdr.length); > > if (!rc) { > > inode = d_backing_inode(dentry); > > > > @@ -268,8 +281,11 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > else > > evm_status = INTEGRITY_FAIL; > > } > > - pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length, > > - digest.digest); > > + pr_debug("digest: (%d) [%*phN]\n", digest_ptr->hdr.length, > > + digest_ptr->hdr.length, digest_ptr->digest); > > + > > + if (digest_ptr && digest_ptr != &digest) > > + kfree(digest_ptr); > > What is the actual problem here? Where is a scatterlist being created from this > buffer? AFAICS it never happens. Hi Eric it is in public_key_verify_signature(), called by asymmetric_verify() and integrity_digsig_verify(). Roberto
On Fri, Dec 02, 2022 at 08:58:21AM +0100, Roberto Sassu wrote: > On Thu, 2022-12-01 at 10:53 -0800, Eric Biggers wrote: > > On Thu, Dec 01, 2022 at 11:06:24AM +0100, Roberto Sassu wrote: > > > From: Roberto Sassu <roberto.sassu@huawei.com> > > > > > > Commit ac4e97abce9b8 ("scatterlist: sg_set_buf() argument must be in linear > > > mapping") checks that both the signature and the digest reside in the > > > linear mapping area. > > > > > > However, more recently commit ba14a194a434c ("fork: Add generic vmalloced > > > stack support"), made it possible to move the stack in the vmalloc area, > > > which is not contiguous, and thus not suitable for sg_set_buf() which needs > > > adjacent pages. > > > > > > Fix this by checking if CONFIG_VMAP_STACK is enabled. If yes, allocate an > > > evm_digest structure, and use that instead of the in-stack counterpart. > > > > > > Cc: stable@vger.kernel.org # 4.9.x > > > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support") > > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > > > --- > > > security/integrity/evm/evm_main.c | 26 +++++++++++++++++++++----- > > > 1 file changed, 21 insertions(+), 5 deletions(-) > > > > > > diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c > > > index 23d484e05e6f..7f76d6103f2e 100644 > > > --- a/security/integrity/evm/evm_main.c > > > +++ b/security/integrity/evm/evm_main.c > > > @@ -174,6 +174,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > struct signature_v2_hdr *hdr; > > > enum integrity_status evm_status = INTEGRITY_PASS; > > > struct evm_digest digest; > > > + struct evm_digest *digest_ptr = &digest; > > > struct inode *inode; > > > int rc, xattr_len, evm_immutable = 0; > > > > > > @@ -231,14 +232,26 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > } > > > > > > hdr = (struct signature_v2_hdr *)xattr_data; > > > - digest.hdr.algo = hdr->hash_algo; > > > + > > > + if (IS_ENABLED(CONFIG_VMAP_STACK)) { > > > + digest_ptr = kmalloc(sizeof(*digest_ptr), GFP_NOFS); > > > + if (!digest_ptr) { > > > + rc = -ENOMEM; > > > + break; > > > + } > > > + } > > > + > > > + digest_ptr->hdr.algo = hdr->hash_algo; > > > + > > > rc = evm_calc_hash(dentry, xattr_name, xattr_value, > > > - xattr_value_len, xattr_data->type, &digest); > > > + xattr_value_len, xattr_data->type, > > > + digest_ptr); > > > if (rc) > > > break; > > > rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM, > > > (const char *)xattr_data, xattr_len, > > > - digest.digest, digest.hdr.length); > > > + digest_ptr->digest, > > > + digest_ptr->hdr.length); > > > if (!rc) { > > > inode = d_backing_inode(dentry); > > > > > > @@ -268,8 +281,11 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > else > > > evm_status = INTEGRITY_FAIL; > > > } > > > - pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length, > > > - digest.digest); > > > + pr_debug("digest: (%d) [%*phN]\n", digest_ptr->hdr.length, > > > + digest_ptr->hdr.length, digest_ptr->digest); > > > + > > > + if (digest_ptr && digest_ptr != &digest) > > > + kfree(digest_ptr); > > > > What is the actual problem here? Where is a scatterlist being created from this > > buffer? AFAICS it never happens. > > Hi Eric > > it is in public_key_verify_signature(), called by asymmetric_verify() > and integrity_digsig_verify(). > Hmm, that's several steps down the stack then. And not something I had expected. Perhaps this should be fixed in public_key_verify_signature() instead? It already does a kmalloc(), so that allocation size just could be made a bit larger to get space for a temporary copy of 's' and 'digest'. Or at the very least, struct public_key_signature should have a *very* clear comment saying that the 's' and 'digest' fields must be located in physically contiguous memory... - Eric
On Fri, 2022-12-02 at 10:49 -0800, Eric Biggers wrote: > On Fri, Dec 02, 2022 at 08:58:21AM +0100, Roberto Sassu wrote: > > On Thu, 2022-12-01 at 10:53 -0800, Eric Biggers wrote: > > > On Thu, Dec 01, 2022 at 11:06:24AM +0100, Roberto Sassu wrote: > > > > From: Roberto Sassu <roberto.sassu@huawei.com> > > > > > > > > Commit ac4e97abce9b8 ("scatterlist: sg_set_buf() argument must be in linear > > > > mapping") checks that both the signature and the digest reside in the > > > > linear mapping area. > > > > > > > > However, more recently commit ba14a194a434c ("fork: Add generic vmalloced > > > > stack support"), made it possible to move the stack in the vmalloc area, > > > > which is not contiguous, and thus not suitable for sg_set_buf() which needs > > > > adjacent pages. > > > > > > > > Fix this by checking if CONFIG_VMAP_STACK is enabled. If yes, allocate an > > > > evm_digest structure, and use that instead of the in-stack counterpart. > > > > > > > > Cc: stable@vger.kernel.org # 4.9.x > > > > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support") > > > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > > > > --- > > > > security/integrity/evm/evm_main.c | 26 +++++++++++++++++++++----- > > > > 1 file changed, 21 insertions(+), 5 deletions(-) > > > > > > > > diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c > > > > index 23d484e05e6f..7f76d6103f2e 100644 > > > > --- a/security/integrity/evm/evm_main.c > > > > +++ b/security/integrity/evm/evm_main.c > > > > @@ -174,6 +174,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > > struct signature_v2_hdr *hdr; > > > > enum integrity_status evm_status = INTEGRITY_PASS; > > > > struct evm_digest digest; > > > > + struct evm_digest *digest_ptr = &digest; > > > > struct inode *inode; > > > > int rc, xattr_len, evm_immutable = 0; > > > > > > > > @@ -231,14 +232,26 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > > } > > > > > > > > hdr = (struct signature_v2_hdr *)xattr_data; > > > > - digest.hdr.algo = hdr->hash_algo; > > > > + > > > > + if (IS_ENABLED(CONFIG_VMAP_STACK)) { > > > > + digest_ptr = kmalloc(sizeof(*digest_ptr), GFP_NOFS); > > > > + if (!digest_ptr) { > > > > + rc = -ENOMEM; > > > > + break; > > > > + } > > > > + } > > > > + > > > > + digest_ptr->hdr.algo = hdr->hash_algo; > > > > + > > > > rc = evm_calc_hash(dentry, xattr_name, xattr_value, > > > > - xattr_value_len, xattr_data->type, &digest); > > > > + xattr_value_len, xattr_data->type, > > > > + digest_ptr); > > > > if (rc) > > > > break; > > > > rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM, > > > > (const char *)xattr_data, xattr_len, > > > > - digest.digest, digest.hdr.length); > > > > + digest_ptr->digest, > > > > + digest_ptr->hdr.length); > > > > if (!rc) { > > > > inode = d_backing_inode(dentry); > > > > > > > > @@ -268,8 +281,11 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > > else > > > > evm_status = INTEGRITY_FAIL; > > > > } > > > > - pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length, > > > > - digest.digest); > > > > + pr_debug("digest: (%d) [%*phN]\n", digest_ptr->hdr.length, > > > > + digest_ptr->hdr.length, digest_ptr->digest); > > > > + > > > > + if (digest_ptr && digest_ptr != &digest) > > > > + kfree(digest_ptr); > > > > > > What is the actual problem here? Where is a scatterlist being created from this > > > buffer? AFAICS it never happens. > > > > Hi Eric > > > > it is in public_key_verify_signature(), called by asymmetric_verify() > > and integrity_digsig_verify(). > > > > Hmm, that's several steps down the stack then. And not something I had > expected. > > Perhaps this should be fixed in public_key_verify_signature() instead? It > already does a kmalloc(), so that allocation size just could be made a bit > larger to get space for a temporary copy of 's' and 'digest'. Mimi asked to fix it in both IMA and EVM. > Or at the very least, struct public_key_signature should have a *very* clear > comment saying that the 's' and 'digest' fields must be located in physically > contiguous memory... That I could add as an additional patch. Thanks Roberto
On Mon, 2022-12-05 at 09:22 +0100, Roberto Sassu wrote: > On Fri, 2022-12-02 at 10:49 -0800, Eric Biggers wrote: > > On Fri, Dec 02, 2022 at 08:58:21AM +0100, Roberto Sassu wrote: > > > On Thu, 2022-12-01 at 10:53 -0800, Eric Biggers wrote: > > > > On Thu, Dec 01, 2022 at 11:06:24AM +0100, Roberto Sassu wrote: > > > > > From: Roberto Sassu <roberto.sassu@huawei.com> > > > > > > > > > > Commit ac4e97abce9b8 ("scatterlist: sg_set_buf() argument must be in linear > > > > > mapping") checks that both the signature and the digest reside in the > > > > > linear mapping area. > > > > > > > > > > However, more recently commit ba14a194a434c ("fork: Add generic vmalloced > > > > > stack support"), made it possible to move the stack in the vmalloc area, > > > > > which is not contiguous, and thus not suitable for sg_set_buf() which needs > > > > > adjacent pages. > > > > > > > > > > Fix this by checking if CONFIG_VMAP_STACK is enabled. If yes, allocate an > > > > > evm_digest structure, and use that instead of the in-stack counterpart. > > > > > > > > > > Cc: stable@vger.kernel.org # 4.9.x > > > > > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support") > > > > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > > > > > --- > > > > > security/integrity/evm/evm_main.c | 26 +++++++++++++++++++++----- > > > > > 1 file changed, 21 insertions(+), 5 deletions(-) > > > > > > > > > > diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c > > > > > index 23d484e05e6f..7f76d6103f2e 100644 > > > > > --- a/security/integrity/evm/evm_main.c > > > > > +++ b/security/integrity/evm/evm_main.c > > > > > @@ -174,6 +174,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > > > struct signature_v2_hdr *hdr; > > > > > enum integrity_status evm_status = INTEGRITY_PASS; > > > > > struct evm_digest digest; > > > > > + struct evm_digest *digest_ptr = &digest; > > > > > struct inode *inode; > > > > > int rc, xattr_len, evm_immutable = 0; > > > > > > > > > > @@ -231,14 +232,26 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > > > } > > > > > > > > > > hdr = (struct signature_v2_hdr *)xattr_data; > > > > > - digest.hdr.algo = hdr->hash_algo; > > > > > + > > > > > + if (IS_ENABLED(CONFIG_VMAP_STACK)) { > > > > > + digest_ptr = kmalloc(sizeof(*digest_ptr), GFP_NOFS); > > > > > + if (!digest_ptr) { > > > > > + rc = -ENOMEM; > > > > > + break; > > > > > + } > > > > > + } > > > > > + > > > > > + digest_ptr->hdr.algo = hdr->hash_algo; > > > > > + > > > > > rc = evm_calc_hash(dentry, xattr_name, xattr_value, > > > > > - xattr_value_len, xattr_data->type, &digest); > > > > > + xattr_value_len, xattr_data->type, > > > > > + digest_ptr); > > > > > if (rc) > > > > > break; > > > > > rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM, > > > > > (const char *)xattr_data, xattr_len, > > > > > - digest.digest, digest.hdr.length); > > > > > + digest_ptr->digest, > > > > > + digest_ptr->hdr.length); > > > > > if (!rc) { > > > > > inode = d_backing_inode(dentry); > > > > > > > > > > @@ -268,8 +281,11 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > > > else > > > > > evm_status = INTEGRITY_FAIL; > > > > > } > > > > > - pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length, > > > > > - digest.digest); > > > > > + pr_debug("digest: (%d) [%*phN]\n", digest_ptr->hdr.length, > > > > > + digest_ptr->hdr.length, digest_ptr->digest); > > > > > + > > > > > + if (digest_ptr && digest_ptr != &digest) > > > > > + kfree(digest_ptr); > > > > > > > > What is the actual problem here? Where is a scatterlist being created from this > > > > buffer? AFAICS it never happens. > > > > > > Hi Eric > > > > > > it is in public_key_verify_signature(), called by asymmetric_verify() > > > and integrity_digsig_verify(). > > > > > > > Hmm, that's several steps down the stack then. And not something I had > > expected. > > > > Perhaps this should be fixed in public_key_verify_signature() instead? It > > already does a kmalloc(), so that allocation size just could be made a bit > > larger to get space for a temporary copy of 's' and 'digest'. > > Mimi asked to fix it in both IMA and EVM. At the time I thought the problem was limited to integrity_digsig_verify() and just to the digest. I'll leave it up to you and Eric to decide what is the preferable solution. > > > Or at the very least, struct public_key_signature should have a *very* clear > > comment saying that the 's' and 'digest' fields must be located in physically > > contiguous memory... > > That I could add as an additional patch. Thanks, the new patch containing the comment looks fine.
On Wed, 2022-12-07 at 20:26 -0500, Mimi Zohar wrote: > On Mon, 2022-12-05 at 09:22 +0100, Roberto Sassu wrote: > > On Fri, 2022-12-02 at 10:49 -0800, Eric Biggers wrote: > > > On Fri, Dec 02, 2022 at 08:58:21AM +0100, Roberto Sassu wrote: > > > > On Thu, 2022-12-01 at 10:53 -0800, Eric Biggers wrote: > > > > > On Thu, Dec 01, 2022 at 11:06:24AM +0100, Roberto Sassu wrote: > > > > > > From: Roberto Sassu <roberto.sassu@huawei.com> > > > > > > > > > > > > Commit ac4e97abce9b8 ("scatterlist: sg_set_buf() argument must be in linear > > > > > > mapping") checks that both the signature and the digest reside in the > > > > > > linear mapping area. > > > > > > > > > > > > However, more recently commit ba14a194a434c ("fork: Add generic vmalloced > > > > > > stack support"), made it possible to move the stack in the vmalloc area, > > > > > > which is not contiguous, and thus not suitable for sg_set_buf() which needs > > > > > > adjacent pages. > > > > > > > > > > > > Fix this by checking if CONFIG_VMAP_STACK is enabled. If yes, allocate an > > > > > > evm_digest structure, and use that instead of the in-stack counterpart. > > > > > > > > > > > > Cc: stable@vger.kernel.org # 4.9.x > > > > > > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support") > > > > > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > > > > > > --- > > > > > > security/integrity/evm/evm_main.c | 26 +++++++++++++++++++++----- > > > > > > 1 file changed, 21 insertions(+), 5 deletions(-) > > > > > > > > > > > > diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c > > > > > > index 23d484e05e6f..7f76d6103f2e 100644 > > > > > > --- a/security/integrity/evm/evm_main.c > > > > > > +++ b/security/integrity/evm/evm_main.c > > > > > > @@ -174,6 +174,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > > > > struct signature_v2_hdr *hdr; > > > > > > enum integrity_status evm_status = INTEGRITY_PASS; > > > > > > struct evm_digest digest; > > > > > > + struct evm_digest *digest_ptr = &digest; > > > > > > struct inode *inode; > > > > > > int rc, xattr_len, evm_immutable = 0; > > > > > > > > > > > > @@ -231,14 +232,26 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > > > > } > > > > > > > > > > > > hdr = (struct signature_v2_hdr *)xattr_data; > > > > > > - digest.hdr.algo = hdr->hash_algo; > > > > > > + > > > > > > + if (IS_ENABLED(CONFIG_VMAP_STACK)) { > > > > > > + digest_ptr = kmalloc(sizeof(*digest_ptr), GFP_NOFS); > > > > > > + if (!digest_ptr) { > > > > > > + rc = -ENOMEM; > > > > > > + break; > > > > > > + } > > > > > > + } > > > > > > + > > > > > > + digest_ptr->hdr.algo = hdr->hash_algo; > > > > > > + > > > > > > rc = evm_calc_hash(dentry, xattr_name, xattr_value, > > > > > > - xattr_value_len, xattr_data->type, &digest); > > > > > > + xattr_value_len, xattr_data->type, > > > > > > + digest_ptr); > > > > > > if (rc) > > > > > > break; > > > > > > rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM, > > > > > > (const char *)xattr_data, xattr_len, > > > > > > - digest.digest, digest.hdr.length); > > > > > > + digest_ptr->digest, > > > > > > + digest_ptr->hdr.length); > > > > > > if (!rc) { > > > > > > inode = d_backing_inode(dentry); > > > > > > > > > > > > @@ -268,8 +281,11 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > > > > else > > > > > > evm_status = INTEGRITY_FAIL; > > > > > > } > > > > > > - pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length, > > > > > > - digest.digest); > > > > > > + pr_debug("digest: (%d) [%*phN]\n", digest_ptr->hdr.length, > > > > > > + digest_ptr->hdr.length, digest_ptr->digest); > > > > > > + > > > > > > + if (digest_ptr && digest_ptr != &digest) > > > > > > + kfree(digest_ptr); > > > > > > > > > > What is the actual problem here? Where is a scatterlist being created from this > > > > > buffer? AFAICS it never happens. > > > > > > > > Hi Eric > > > > > > > > it is in public_key_verify_signature(), called by asymmetric_verify() > > > > and integrity_digsig_verify(). > > > > > > > > > > Hmm, that's several steps down the stack then. And not something I had > > > expected. > > > > > > Perhaps this should be fixed in public_key_verify_signature() instead? It > > > already does a kmalloc(), so that allocation size just could be made a bit > > > larger to get space for a temporary copy of 's' and 'digest'. > > > > Mimi asked to fix it in both IMA and EVM. > > At the time I thought the problem was limited to > integrity_digsig_verify() and just to the digest. > > I'll leave it up to you and Eric to decide what is the preferable > solution. Ok, yes. I think Eric's suggestion of making a copy in public_key_verify_signature() is better. Will do it. > > > Or at the very least, struct public_key_signature should have a *very* clear > > > comment saying that the 's' and 'digest' fields must be located in physically > > > contiguous memory... > > > > That I could add as an additional patch. > > Thanks, the new patch containing the comment looks fine. Thanks, not sure if I need to keep it with the new patch (probably not). Roberto
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c index 23d484e05e6f..7f76d6103f2e 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -174,6 +174,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, struct signature_v2_hdr *hdr; enum integrity_status evm_status = INTEGRITY_PASS; struct evm_digest digest; + struct evm_digest *digest_ptr = &digest; struct inode *inode; int rc, xattr_len, evm_immutable = 0; @@ -231,14 +232,26 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, } hdr = (struct signature_v2_hdr *)xattr_data; - digest.hdr.algo = hdr->hash_algo; + + if (IS_ENABLED(CONFIG_VMAP_STACK)) { + digest_ptr = kmalloc(sizeof(*digest_ptr), GFP_NOFS); + if (!digest_ptr) { + rc = -ENOMEM; + break; + } + } + + digest_ptr->hdr.algo = hdr->hash_algo; + rc = evm_calc_hash(dentry, xattr_name, xattr_value, - xattr_value_len, xattr_data->type, &digest); + xattr_value_len, xattr_data->type, + digest_ptr); if (rc) break; rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM, (const char *)xattr_data, xattr_len, - digest.digest, digest.hdr.length); + digest_ptr->digest, + digest_ptr->hdr.length); if (!rc) { inode = d_backing_inode(dentry); @@ -268,8 +281,11 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, else evm_status = INTEGRITY_FAIL; } - pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length, - digest.digest); + pr_debug("digest: (%d) [%*phN]\n", digest_ptr->hdr.length, + digest_ptr->hdr.length, digest_ptr->digest); + + if (digest_ptr && digest_ptr != &digest) + kfree(digest_ptr); out: if (iint) iint->evm_status = evm_status;