On Thu, Mar 4, 2021 at 12:23 AM Andrew Morton <akpm(a)linux-foundation.org> wrote:
>
> On Fri, 26 Feb 2021 02:25:37 +0100 Andrey Konovalov <andreyknvl(a)google.com> wrote:
>
> > Currently, kasan_free_nondeferred_pages()->kasan_free_pages() is called
> > after debug_pagealloc_unmap_pages(). This causes a crash when
> > debug_pagealloc is enabled, as HW_TAGS KASAN can't set tags on an
> > unmapped page.
> >
> > This patch puts kasan_free_nondeferred_pages() before
> > debug_pagealloc_unmap_pages().
> >
> > Besides fixing the crash, this also makes the annotation order consistent
> > with debug_pagealloc_map_pages() preceding kasan_alloc_pages().
> >
>
> This bug exists in 5.12, does it not?
>
> If so, is cc:stable appropriate and if so, do we have a suitable Fixes:
> commit?
Sure:
Fixes: 94ab5b61ee16 ("kasan, arm64: enable CONFIG_KASAN_HW_TAGS")
Cc: <stable(a)vger.kernel.org>
EVM_ALLOW_METADATA_WRITES is an EVM initialization flag that can be set to
temporarily disable metadata verification until all xattrs/attrs necessary
to verify an EVM portable signature are copied to the file. This flag is
cleared when EVM is initialized with an HMAC key, to avoid that the HMAC is
calculated on unverified xattrs/attrs.
Currently EVM unnecessarily denies setting this flag if EVM is initialized
with a public key, which is not a concern as it cannot be used to trust
xattrs/attrs updates. This patch removes this limitation.
Cc: stable(a)vger.kernel.org # 4.16.x
Fixes: ae1ba1676b88e ("EVM: Allow userland to permit modification of EVM-protected metadata")
Signed-off-by: Roberto Sassu <roberto.sassu(a)huawei.com>
---
Documentation/ABI/testing/evm | 5 +++--
security/integrity/evm/evm_secfs.c | 4 ++--
2 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/Documentation/ABI/testing/evm b/Documentation/ABI/testing/evm
index 3c477ba48a31..eb6d70fd6fa2 100644
--- a/Documentation/ABI/testing/evm
+++ b/Documentation/ABI/testing/evm
@@ -49,8 +49,9 @@ Description:
modification of EVM-protected metadata and
disable all further modification of policy
- Note that once a key has been loaded, it will no longer be
- possible to enable metadata modification.
+ Note that once an HMAC key has been loaded, it will no longer
+ be possible to enable metadata modification and, if it is
+ already enabled, it will be disabled.
Until key loading has been signaled EVM can not create
or validate the 'security.evm' xattr, but returns
diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c
index bbc85637e18b..197a4b83e534 100644
--- a/security/integrity/evm/evm_secfs.c
+++ b/security/integrity/evm/evm_secfs.c
@@ -81,10 +81,10 @@ static ssize_t evm_write_key(struct file *file, const char __user *buf,
return -EINVAL;
/* Don't allow a request to freshly enable metadata writes if
- * keys are loaded.
+ * an HMAC key is loaded.
*/
if ((i & EVM_ALLOW_METADATA_WRITES) &&
- ((evm_initialized & EVM_KEY_MASK) != 0) &&
+ ((evm_initialized & EVM_INIT_HMAC) != 0) &&
!(evm_initialized & EVM_ALLOW_METADATA_WRITES))
return -EPERM;
--
2.26.2
evm_inode_init_security() requires an HMAC key to calculate the HMAC on
initial xattrs provided by LSMs. However, it checks generically whether a
key has been loaded, including also public keys, which is not correct as
public keys are not suitable to calculate the HMAC.
Originally, support for signature verification was introduced to verify a
possibly immutable initial ram disk, when no new files are created, and to
switch to HMAC for the root filesystem. By that time, an HMAC key should
have been loaded and usable to calculate HMACs for new files.
More recently support for requiring an HMAC key was removed from the
kernel, so that signature verification can be used alone. Since this is a
legitimate use case, evm_inode_init_security() should not return an error
when no HMAC key has been loaded.
This patch fixes this problem by replacing the evm_key_loaded() check with
a check of the EVM_INIT_HMAC flag in evm_initialized.
Cc: stable(a)vger.kernel.org # 4.5.x
Fixes: 26ddabfe96b ("evm: enable EVM when X509 certificate is loaded")
Signed-off-by: Roberto Sassu <roberto.sassu(a)huawei.com>
Reviewed-by: Mimi Zohar <zohar(a)linux.ibm.com>
---
security/integrity/evm/evm_main.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 0de367aaa2d3..7ac5204c8d1f 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -521,7 +521,7 @@ void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
}
/*
- * evm_inode_init_security - initializes security.evm
+ * evm_inode_init_security - initializes security.evm HMAC value
*/
int evm_inode_init_security(struct inode *inode,
const struct xattr *lsm_xattr,
@@ -530,7 +530,8 @@ int evm_inode_init_security(struct inode *inode,
struct evm_xattr *xattr_data;
int rc;
- if (!evm_key_loaded() || !evm_protected_xattr(lsm_xattr->name))
+ if (!(evm_initialized & EVM_INIT_HMAC) ||
+ !evm_protected_xattr(lsm_xattr->name))
return 0;
xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
--
2.26.2