From: Roberto Sassu <[email protected]>
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: [email protected] # 4.9.x
Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support")
Signed-off-by: Roberto Sassu <[email protected]>
---
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);
out:
if (iint)
iint->evm_status = evm_status;
--
2.25.1
On Thu, Dec 01, 2022 at 11:06:24AM +0100, Roberto Sassu wrote:
> From: Roberto Sassu <[email protected]>
>
> 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: [email protected] # 4.9.x
> Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support")
> Signed-off-by: Roberto Sassu <[email protected]>
> ---
> 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 <[email protected]>
> >
> > 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: [email protected] # 4.9.x
> > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support")
> > Signed-off-by: Roberto Sassu <[email protected]>
> > ---
> > 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").
--
thanks,
Mimi
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 <[email protected]>
> > >
> > > 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: [email protected] # 4.9.x
> > > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support")
> > > Signed-off-by: Roberto Sassu <[email protected]>
> > > ---
> > > 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 <[email protected]>
> >
> > 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: [email protected] # 4.9.x
> > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support")
> > Signed-off-by: Roberto Sassu <[email protected]>
> > ---
> > 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 <[email protected]>
> > >
> > > 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: [email protected] # 4.9.x
> > > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support")
> > > Signed-off-by: Roberto Sassu <[email protected]>
> > > ---
> > > 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 <[email protected]>
> > > >
> > > > 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: [email protected] # 4.9.x
> > > > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support")
> > > > Signed-off-by: Roberto Sassu <[email protected]>
> > > > ---
> > > > 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 <[email protected]>
> > > > >
> > > > > 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: [email protected] # 4.9.x
> > > > > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support")
> > > > > Signed-off-by: Roberto Sassu <[email protected]>
> > > > > ---
> > > > > 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.
--
thanks,
Mimi
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 <[email protected]>
> > > > > >
> > > > > > 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: [email protected] # 4.9.x
> > > > > > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support")
> > > > > > Signed-off-by: Roberto Sassu <[email protected]>
> > > > > > ---
> > > > > > 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