[PATCH v12 0/4] evm: Do HMAC of multiple per LSM xattrs for new inodes

[PATCH v12 0/4] evm: Do HMAC of multiple per LSM xattrs for new inodes

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu@huawei.com>

One of the major goals of LSM stacking is to run multiple LSMs side by side
without interfering with each other. The ultimate decision will depend on
individual LSM decision.

Several changes need to be made to the LSM infrastructure to be able to
support that. This patch set tackles one of them: gives to each LSM the
ability to specify one or multiple xattrs to be set at inode creation
time and, at the same time, gives to EVM the ability to access all those
xattrs and calculate the HMAC on them.

The first problem that this patch set addresses is to make the
inode_init_security hook definition suitable to use with EVM which, unlike
other LSMs, needs to have visibility of all xattrs and not only the one
that the LSM infrastructure passes to the LSM to be set.

The solution is to replace in the inode_init_security definition the
name/value/len parameters with the beginning of the array containing all
xattrs set by LSMs. Due to security_old_inode_init_security() API
limitation of setting only one xattr, it has been dropped and the remaining
users, ocfs2 and reiserfs, switch to security_inode_init_security().
However, due to the complexity of the changes required to fully exploit the
ability of security_inode_init_security() to set multiple xattrs, those
users can still set only one xattr (the first set in the xattr array) where
previously they called security_old_inode_init_security().

Furthermore, while EVM is invoked unlike before, its xattr will not be set
as it would not be the first set in the xattr array, or if it is the first,
there would not be protected xattrs to calculate the HMAC on.

The second problem this patch set addresses is the limitation of the
call_int_hook() of stopping the loop when the return value from a hook
implementation is not zero. Unfortunately, for the inode_init_security hook
it is a legitimate case to return -EOPNOTSUPP, but this would not
necessarily mean that there is an error to report to the LSM infrastructure
but just that an LSM does not will to set an xattr. Other LSMs should be
still consulted as well.

The solution for this specific case is to replace the call_int_hook() with
the loop itself, so that -EOPNOTSUPP can be ignored. In addition, the
default return value of inode_init_security was changed to -EOPNOTSUPP, so
that BPF LSM follows the return value convention.

Next, this patch set removes the limitation of creating only two xattrs,
one by an active LSM and another by EVM. This patch set extends the
reservation mechanism of the LSM infrastructure, to allow each LSM to
request one or multiple xattrs. While this could potentially lead to
reaching the filesystem limits of number/size of the xattrs, it seems not
an issue that need to be solved by the LSM infrastructure but by the
filesystems themselves. Currently, if the limit is reached, the only
workaround would be to use fewer LSMs.

The reservation mechanism concept would have made it very easy for LSMs to
position themselves correctly in the xattr array, as the LSM infrastructure
at initialization time changes the number of xattrs requested by each LSM
with an offset.

However, this opens for the possibility of having gaps in the xattr array,
due to the fact that an LSM can request xattr slots to the LSM
infrastructure but not fill them (if it was loaded but not initialized).

Instead, the decision was to add an additional parameter to the
inode_init_security_hook, the number of filled slots in the xattr array,
which each LSM is expected to update for each xattr it provides. In this
way, the next LSM starts to fill after the last filled slot, regardless of
whether previous LSMs were initialized or not. SELinux, Smack and EVM have
been updated to use this new mechanism.

Finally, this patch set modifies the evm_inode_init_security() definition
to be compatible with the inode_init_security hook definition and adds
support for scanning the whole xattr array and for calculating the HMAC
on all xattrs provided by LSMs.

This patch set has been tested by introducing several instances of a
TestLSM (some providing an xattr, some not, one providing multiple xattrs
and another providing an xattr but in a disabled state). The patch is not
included in this set but it is available here:

https://github.com/robertosassu/linux/commit/011adfbfa30f61c80c900db9a78f4f51b5463a4a

The test, added to ima-evm-utils, is available here:

https://github.com/robertosassu/ima-evm-utils/blob/evm-multiple-lsms-v11-devel-v8/tests/evm_multiple_lsms.test

The test takes a UML kernel built by Github Actions and launches it several
times, each time with a different combination of LSMs and filesystems (ext4,
reiserfs, ocfs2). After boot, it first checks that there is an xattr for each
LSM providing it (for reiserfs and ocfs2 just the first LSM), and then (for
ext4) calculates the HMAC in user space and compares it with the HMAC
calculated by EVM in kernel space.

A test report can be obtained here (the Tumbleweed failure is unrelated):

https://github.com/robertosassu/ima-evm-utils/actions/runs/5164716489/jobs/9304130400

Another test, added to ima-evm-utils, is:

https://github.com/robertosassu/ima-evm-utils/blob/evm-multiple-lsms-v11-devel-v8/tests/evm_hmac.test

Other than doing a simple check, by comparing the EVM HMAC obtained from
ima-evm-utils and from the kernel, it also checks that the EVM HMAC is
still valid after a successful directory transmuting with Smack. If EVM
checked the HMAC of directories, it would have found an invalid HMAC
without patch 2 applied.

The patch set has been tested with both the SElinux and Smack test suites.
Below, there is the summary of the test results:

SELinux Test Suite result (without patches):
All tests successful.
Files=76, Tests=1357, 224 wallclock secs ( 0.42 usr  0.13 sys + 11.96 cusr 15.02 csys = 27.53 CPU)
Result: PASS

All tests successful.
Files=76, Tests=1357, 224 wallclock secs ( 0.40 usr  0.12 sys + 11.86 cusr 14.71 csys = 27.09 CPU)
Result: PASS

Smack Test Suite result (without patches):
95 Passed, 0 Failed, 100% Success rate

Smack Test Suite result (with patches):
95 Passed, 0 Failed, 100% Success rate

Changelog

v11 (quickly tested, only stylistic issues):
- Fix stylistic issues reported by checkpatch.pl --strict (suggested by
  Mimi)
- Avoid pointer math in lsm_get_xattr_slot() (suggested by Paul)

v10:
- Remove check for -EOPNOTSUPP by evm_inode_init_security() in
  security_inode_init_security() (suggested by Mimi)
- Adjust formatting of Smack xattrs description (suggested by Paul)
- Change value of SMACK_INODE_INIT_XATTRS from 4 to 2 (suggested by Paul)
- Add patch to set SMACK64TRANSMUTE in smack_inode_init_security()
- Replace new_xattrs + count with &new_xattrs[xattr_count] in patch 1
  (suggested by Paul)

v9:
- Ensure in reiserfs_security_write() that the full xattr name is not
  larger than XATTR_NAME_MAX
- Rename num_filled_xattrs to xattr_count everywhere (suggested by Paul)
- Rename lsm_find_xattr_slot() to lsm_get_xattr_slot() and add a proper
  documentation (suggested by Paul)
- Return zero instead of -EOPNOTSUPP in evm_inode_init_security()
  (suggested by Paul)
- Remove additional checks of new_xattrs array in
  security_inode_init_security() (suggested by Paul)
- Handle the !initxattrs case similarly to the initxattrs case, except for
  not allocating the new_xattrs array in the former (suggested by Paul)
- Remove local variable xattr in security_inode_init_security(), and use
  xattr_count instead for loop termination (suggested by Paul)

v8:
- Add a new reiserfs patch to write the full xattr name
- Add num_filled_xattrs parameter to inode_init_security hook (suggested by
  Paul) and evm_inode_init_security()
- Change default return value of inode_init_security hook to -EOPNOTSUPP
- Rename lbs_xattr field of lsm_blob_sizes to lbs_xattr_count
- Introduce lsm_find_xattr_slot() helper
- Rename lsm_xattr parameter of evm_init_hmac() to xattrs
- Retrieve the EVM xattr slot with lsm_find_xattr_slot() and double check
  with the xattr array terminator
- Remove security_check_compact_filled_xattrs() (suggested by Paul)
- Update security_inode_init_security() documentation
- Ensure that inode_init_security hook incremented the number of filled
  slots if it returned zero
- Ensure that xattr name and value are non-NULL in the filled slots
- Add the xattr name assignment after the xattr value one (suggested by
  Paul)
- Drop patches 1 - 3 (already in lsm/next)

v7:
- Add a patch dependency comment in patch 1 (suggested by Mimi)
- Restore check of -EOPNOTSUPP status in ocfs2_mknod() and ocfs2_symlink()
  (reported by Mimi)
- Add explanation in evm_inode_init_security() why walking through the
  xattrs array is safe (suggested by Mimi)
- Document the lbs_xattr field of struct lsm_blob_sizes (suggested by
  Casey)
- Move documentation changes of the inode_init_security hook to security.c,
  after LSM documentation reorganization by Paul
- Use attributes in plural form in the description of the xattrs parameter
  of smack_inode_init_security()
- Check xattr name instead of xattr value in evm_inode_init_security(),
  for consistency with evm_init_hmac(); equivalent, since
  security_check_compact_filled_xattrs() rejects xattrs with xattr name
  NULL and value not NULL, and viceversa

v6:
- Add a comment in Smack to introduce its xattrs (suggested by Casey)
- Document the overloaded meaning of -EOPNOTSUPP in
  security_inode_init_security() (suggested by Mimi)

v5:
- Modify the cover letter to explain that the goal of this patch set is
  supporting multiple per LSM xattrs in EVM, and not moving IMA and EVM to
  the LSM infrastructure (suggested by Mimi)
- Remove references in the patches description about moving IMA and EVM
  to the LSM infrastructure (suggested by Mimi)
- Explain that the additional EVM invocation due to the switch to
  security_inode_init_security() will not cause the EVM xattr to be added
  (suggested by Mimi)

v4:
- Remove patch to call reiserfs_security_free(), already queued
- Switch ocfs2 and reiserfs to security_inode_init_security() (suggested by
  Mimi)
- Remove security_old_inode_init_security() (suggested by Paul)
- Rename security_check_compact_xattrs() to
  security_check_compact_filled_xattrs() and add function description
  (suggested by Mimi)
- Rename checked_xattrs parameter of security_check_compact_filled_xattrs()
  to num_filled_xattrs (suggested by Mimi)
- Rename cur_xattrs variable in security_inode_init_security() to
  num_filled_xattrs (suggested by Mimi)

v3:
- Don't free the xattr name in reiserfs_security_free()
- Don't include fs_data parameter in inode_init_security hook
- Don't change evm_inode_init_security(), as it will be removed if EVM is
  stacked
- Fix inode_init_security hook documentation
- Drop lsm_find_xattr_slot(), use simple xattr reservation mechanism and
  introduce security_check_compact_xattrs() to compact the xattr array
- Don't allocate xattr array if LSMs didn't reserve any xattr
- Return zero if initxattrs() is not provided to
  security_inode_init_security(), -EOPNOTSUPP if value is not provided to
  security_old_inode_init_security()
- Request LSMs to fill xattrs if only value (not the triple) is provided to
  security_old_inode_init_security(), to avoid unnecessary memory
  allocation

v2:
- rewrite selinux_old_inode_init_security() to use
  security_inode_init_security()
- add lbs_xattr field to lsm_blob_sizes structure, to give the ability to
  LSMs to reserve slots in the xattr array (suggested by Casey)
- add new parameter base_slot to inode_init_security hook definition

v1:
- add calls to reiserfs_security_free() and initialize sec->value to NULL
  (suggested by Tetsuo and Mimi)
- change definition of inode_init_security hook, replace the name, value
  and len triple with the xattr array (suggested by Casey)
- introduce lsm_find_xattr_slot() helper for LSMs to find an unused slot in
  the passed xattr array

Roberto Sassu (4):
  security: Allow all LSMs to provide xattrs for inode_init_security
    hook
  smack: Set the SMACK64TRANSMUTE xattr in smack_inode_init_security()
  evm: Align evm_inode_init_security() definition with LSM
    infrastructure
  evm: Support multiple LSMs providing an xattr

 include/linux/evm.h                 | 14 +++---
 include/linux/lsm_hook_defs.h       |  6 +--
 include/linux/lsm_hooks.h           | 20 ++++++++
 security/integrity/evm/evm.h        |  4 +-
 security/integrity/evm/evm_crypto.c | 11 ++++-
 security/integrity/evm/evm_main.c   | 39 +++++++++++++---
 security/security.c                 | 71 +++++++++++++++++++----------
 security/selinux/hooks.c            | 17 +++----
 security/smack/smack.h              |  2 +-
 security/smack/smack_lsm.c          | 68 +++++++++++++++------------
 10 files changed, 172 insertions(+), 80 deletions(-)

-- 
2.25.1

[PATCH v12 1/4] security: Allow all LSMs to provide xattrs for inode_init_security hook

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu@huawei.com>

Currently, the LSM infrastructure supports only one LSM providing an xattr
and EVM calculating the HMAC on that xattr, plus other inode metadata.

Allow all LSMs to provide one or multiple xattrs, by extending the security
blob reservation mechanism. Introduce the new lbs_xattr_count field of the
lsm_blob_sizes structure, so that each LSM can specify how many xattrs it
needs, and the LSM infrastructure knows how many xattr slots it should
allocate.

Modify the inode_init_security hook definition, by passing the full
xattr array allocated in security_inode_init_security(), and the current
number of xattr slots in that array filled by LSMs. The first parameter
would allow EVM to access and calculate the HMAC on xattrs supplied by
other LSMs, the second to not leave gaps in the xattr array, when an LSM
requested but did not provide xattrs (e.g. if it is not initialized).

Introduce lsm_get_xattr_slot(), which LSMs can call as many times as the
number specified in the lbs_xattr_count field of the lsm_blob_sizes
structure. During each call, lsm_get_xattr_slot() increments the number of
filled xattrs, so that at the next invocation it returns the next xattr
slot to fill.

Cleanup security_inode_init_security(). Unify the !initxattrs and
initxattrs case by simply not allocating the new_xattrs array in the
former. Update the documentation to reflect the changes, and fix the
description of the xattr name, as it is not allocated anymore.

Adapt both SELinux and Smack to use the new definition of the
inode_init_security hook, and to call lsm_get_xattr_slot() to obtain and
fill the reserved slots in the xattr array.

Move the xattr->name assignment after the xattr->value one, so that it is
done only in case of successful memory allocation.

Finally, change the default return value of the inode_init_security hook
from zero to -EOPNOTSUPP, so that BPF LSM correctly follows the hook
conventions.

Reported-by: Nicolas Bouchinet <nicolas.bouchinet@clip-os.org> (EVM crash)
Link: https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
 include/linux/lsm_hook_defs.h |  6 +--
 include/linux/lsm_hooks.h     | 20 ++++++++++
 security/security.c           | 71 +++++++++++++++++++++++------------
 security/selinux/hooks.c      | 17 +++++----
 security/smack/smack_lsm.c    | 25 ++++++------
 5 files changed, 92 insertions(+), 47 deletions(-)

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 6bb55e61e8e..a1896f90089 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -111,9 +111,9 @@ LSM_HOOK(int, 0, path_notify, const struct path *path, u64 mask,
 	 unsigned int obj_type)
 LSM_HOOK(int, 0, inode_alloc_security, struct inode *inode)
 LSM_HOOK(void, LSM_RET_VOID, inode_free_security, struct inode *inode)
-LSM_HOOK(int, 0, inode_init_security, struct inode *inode,
-	 struct inode *dir, const struct qstr *qstr, const char **name,
-	 void **value, size_t *len)
+LSM_HOOK(int, -EOPNOTSUPP, inode_init_security, struct inode *inode,
+	 struct inode *dir, const struct qstr *qstr, struct xattr *xattrs,
+	 int *xattr_count)
 LSM_HOOK(int, 0, inode_init_security_anon, struct inode *inode,
 	 const struct qstr *name, const struct inode *context_inode)
 LSM_HOOK(int, 0, inode_create, struct inode *dir, struct dentry *dentry,
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index ab2b2fafa4a..dcb5e5b5eb1 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -28,6 +28,7 @@
 #include <linux/security.h>
 #include <linux/init.h>
 #include <linux/rculist.h>
+#include <linux/xattr.h>
 
 union security_list_options {
 	#define LSM_HOOK(RET, DEFAULT, NAME, ...) RET (*NAME)(__VA_ARGS__);
@@ -63,8 +64,27 @@ struct lsm_blob_sizes {
 	int	lbs_ipc;
 	int	lbs_msg_msg;
 	int	lbs_task;
+	int	lbs_xattr_count; /* number of xattr slots in new_xattrs array */
 };
 
+/**
+ * lsm_get_xattr_slot - Return the next available slot and increment the index
+ * @xattrs: array storing LSM-provided xattrs
+ * @xattr_count: number of already stored xattrs (updated)
+ *
+ * Retrieve the first available slot in the @xattrs array to fill with an xattr,
+ * and increment @xattr_count.
+ *
+ * Return: The slot to fill in @xattrs if non-NULL, NULL otherwise.
+ */
+static inline struct xattr *lsm_get_xattr_slot(struct xattr *xattrs,
+					       int *xattr_count)
+{
+	if (unlikely(!xattrs))
+		return NULL;
+	return &xattrs[(*xattr_count)++];
+}
+
 /*
  * LSM_RET_VOID is used as the default value in LSM_HOOK definitions for void
  * LSM hooks (in include/linux/lsm_hook_defs.h).
diff --git a/security/security.c b/security/security.c
index ee4f1cc4902..d5ef7df1ce4 100644
--- a/security/security.c
+++ b/security/security.c
@@ -31,8 +31,6 @@
 #include <linux/msg.h>
 #include <net/flow.h>
 
-#define MAX_LSM_EVM_XATTR	2
-
 /* How many LSMs were built into the kernel? */
 #define LSM_COUNT (__end_lsm_info - __start_lsm_info)
 
@@ -212,6 +210,8 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed)
 	lsm_set_blob_size(&needed->lbs_msg_msg, &blob_sizes.lbs_msg_msg);
 	lsm_set_blob_size(&needed->lbs_superblock, &blob_sizes.lbs_superblock);
 	lsm_set_blob_size(&needed->lbs_task, &blob_sizes.lbs_task);
+	lsm_set_blob_size(&needed->lbs_xattr_count,
+			  &blob_sizes.lbs_xattr_count);
 }
 
 /* Prepare LSM for initialization. */
@@ -378,6 +378,7 @@ static void __init ordered_lsm_init(void)
 	init_debug("msg_msg blob size    = %d\n", blob_sizes.lbs_msg_msg);
 	init_debug("superblock blob size = %d\n", blob_sizes.lbs_superblock);
 	init_debug("task blob size       = %d\n", blob_sizes.lbs_task);
+	init_debug("xattr slots          = %d\n", blob_sizes.lbs_xattr_count);
 
 	/*
 	 * Create any kmem_caches needed for blobs
@@ -1591,11 +1592,15 @@ EXPORT_SYMBOL(security_dentry_create_files_as);
  * created inode and set up the incore security field for the new inode.  This
  * hook is called by the fs code as part of the inode creation transaction and
  * provides for atomic labeling of the inode, unlike the post_create/mkdir/...
- * hooks called by the VFS.  The hook function is expected to allocate the name
- * and value via kmalloc, with the caller being responsible for calling kfree
- * after using them.  If the security module does not use security attributes
- * or does not wish to put a security attribute on this particular inode, then
- * it should return -EOPNOTSUPP to skip this processing.
+ * hooks called by the VFS.  The hook function is expected to populate the
+ * @xattrs array, by calling lsm_get_xattr_slot() to retrieve the slots
+ * reserved by the security module with the lbs_xattr_count field of the
+ * lsm_blob_sizes structure.  For each slot, the hook function should set ->name
+ * to the attribute name suffix (e.g. selinux), to allocate ->value (will be
+ * freed by the caller) and set it to the attribute value, to set ->value_len to
+ * the length of the value.  If the security module does not use security
+ * attributes or does not wish to put a security attribute on this particular
+ * inode, then it should return -EOPNOTSUPP to skip this processing.
  *
  * Return: Returns 0 on success, -EOPNOTSUPP if no security attribute is
  * needed, or -ENOMEM on memory allocation failure.
@@ -1604,33 +1609,51 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
 				 const struct qstr *qstr,
 				 const initxattrs initxattrs, void *fs_data)
 {
-	struct xattr new_xattrs[MAX_LSM_EVM_XATTR + 1];
-	struct xattr *lsm_xattr, *evm_xattr, *xattr;
-	int ret;
+	struct security_hook_list *P;
+	struct xattr *new_xattrs = NULL;
+	int ret = -EOPNOTSUPP, xattr_count = 0;
 
 	if (unlikely(IS_PRIVATE(inode)))
 		return 0;
 
-	if (!initxattrs)
-		return call_int_hook(inode_init_security, -EOPNOTSUPP, inode,
-				     dir, qstr, NULL, NULL, NULL);
-	memset(new_xattrs, 0, sizeof(new_xattrs));
-	lsm_xattr = new_xattrs;
-	ret = call_int_hook(inode_init_security, -EOPNOTSUPP, inode, dir, qstr,
-			    &lsm_xattr->name,
-			    &lsm_xattr->value,
-			    &lsm_xattr->value_len);
-	if (ret)
+	if (!blob_sizes.lbs_xattr_count)
+		return 0;
+
+	if (initxattrs) {
+		/* Allocate +1 for EVM and +1 as terminator. */
+		new_xattrs = kcalloc(blob_sizes.lbs_xattr_count + 2,
+				     sizeof(*new_xattrs), GFP_NOFS);
+		if (!new_xattrs)
+			return -ENOMEM;
+	}
+
+	hlist_for_each_entry(P, &security_hook_heads.inode_init_security,
+			     list) {
+		ret = P->hook.inode_init_security(inode, dir, qstr, new_xattrs,
+						  &xattr_count);
+		if (ret && ret != -EOPNOTSUPP)
+			goto out;
+		/*
+		 * As documented in lsm_hooks.h, -EOPNOTSUPP in this context
+		 * means that the LSM is not willing to provide an xattr, not
+		 * that it wants to signal an error. Thus, continue to invoke
+		 * the remaining LSMs.
+		 */
+	}
+
+	/* If initxattrs() is NULL, xattr_count is zero, skip the call. */
+	if (!xattr_count)
 		goto out;
 
-	evm_xattr = lsm_xattr + 1;
-	ret = evm_inode_init_security(inode, lsm_xattr, evm_xattr);
+	ret = evm_inode_init_security(inode, new_xattrs,
+				      &new_xattrs[xattr_count]);
 	if (ret)
 		goto out;
 	ret = initxattrs(inode, new_xattrs, fs_data);
 out:
-	for (xattr = new_xattrs; xattr->value != NULL; xattr++)
-		kfree(xattr->value);
+	for (; xattr_count > 0; xattr_count--)
+		kfree(new_xattrs[xattr_count - 1].value);
+	kfree(new_xattrs);
 	return (ret == -EOPNOTSUPP) ? 0 : ret;
 }
 EXPORT_SYMBOL(security_inode_init_security);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 79b4890e993..1d9fe7cdd01 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -104,6 +104,8 @@
 #include "audit.h"
 #include "avc_ss.h"
 
+#define SELINUX_INODE_INIT_XATTRS 1
+
 struct selinux_state selinux_state;
 
 /* SECMARK reference count */
@@ -2823,11 +2825,11 @@ static int selinux_dentry_create_files_as(struct dentry *dentry, int mode,
 
 static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
 				       const struct qstr *qstr,
-				       const char **name,
-				       void **value, size_t *len)
+				       struct xattr *xattrs, int *xattr_count)
 {
 	const struct task_security_struct *tsec = selinux_cred(current_cred());
 	struct superblock_security_struct *sbsec;
+	struct xattr *xattr = lsm_get_xattr_slot(xattrs, xattr_count);
 	u32 newsid, clen;
 	int rc;
 	char *context;
@@ -2854,16 +2856,14 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
 	    !(sbsec->flags & SBLABEL_MNT))
 		return -EOPNOTSUPP;
 
-	if (name)
-		*name = XATTR_SELINUX_SUFFIX;
-
-	if (value && len) {
+	if (xattr) {
 		rc = security_sid_to_context_force(newsid,
 						   &context, &clen);
 		if (rc)
 			return rc;
-		*value = context;
-		*len = clen;
+		xattr->value = context;
+		xattr->value_len = clen;
+		xattr->name = XATTR_SELINUX_SUFFIX;
 	}
 
 	return 0;
@@ -6776,6 +6776,7 @@ struct lsm_blob_sizes selinux_blob_sizes __ro_after_init = {
 	.lbs_ipc = sizeof(struct ipc_security_struct),
 	.lbs_msg_msg = sizeof(struct msg_security_struct),
 	.lbs_superblock = sizeof(struct superblock_security_struct),
+	.lbs_xattr_count = SELINUX_INODE_INIT_XATTRS,
 };
 
 #ifdef CONFIG_PERF_EVENTS
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 6e270cf3fd3..25ade3819af 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -52,6 +52,8 @@
 #define SMK_RECEIVING	1
 #define SMK_SENDING	2
 
+#define SMACK_INODE_INIT_XATTRS 1
+
 #ifdef SMACK_IPV6_PORT_LABELING
 static DEFINE_MUTEX(smack_ipv6_lock);
 static LIST_HEAD(smk_ipv6_port_list);
@@ -923,27 +925,24 @@ static int smack_inode_alloc_security(struct inode *inode)
  * @inode: the newly created inode
  * @dir: containing directory object
  * @qstr: unused
- * @name: where to put the attribute name
- * @value: where to put the attribute value
- * @len: where to put the length of the attribute
+ * @xattrs: where to put the attributes
+ * @xattr_count: current number of LSM-provided xattrs (updated)
  *
  * Returns 0 if it all works out, -ENOMEM if there's no memory
  */
 static int smack_inode_init_security(struct inode *inode, struct inode *dir,
-				     const struct qstr *qstr, const char **name,
-				     void **value, size_t *len)
+				     const struct qstr *qstr,
+				     struct xattr *xattrs, int *xattr_count)
 {
 	struct task_smack *tsp = smack_cred(current_cred());
 	struct inode_smack *issp = smack_inode(inode);
 	struct smack_known *skp = smk_of_task(tsp);
 	struct smack_known *isp = smk_of_inode(inode);
 	struct smack_known *dsp = smk_of_inode(dir);
+	struct xattr *xattr = lsm_get_xattr_slot(xattrs, xattr_count);
 	int may;
 
-	if (name)
-		*name = XATTR_SMACK_SUFFIX;
-
-	if (value && len) {
+	if (xattr) {
 		/*
 		 * If equal, transmuting already occurred in
 		 * smack_dentry_create_files_as(). No need to check again.
@@ -975,11 +974,12 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
 			issp->smk_flags |= SMK_INODE_CHANGED;
 		}
 
-		*value = kstrdup(isp->smk_known, GFP_NOFS);
-		if (*value == NULL)
+		xattr->value = kstrdup(isp->smk_known, GFP_NOFS);
+		if (!xattr->value)
 			return -ENOMEM;
 
-		*len = strlen(isp->smk_known);
+		xattr->value_len = strlen(isp->smk_known);
+		xattr->name = XATTR_SMACK_SUFFIX;
 	}
 
 	return 0;
@@ -4869,6 +4869,7 @@ struct lsm_blob_sizes smack_blob_sizes __ro_after_init = {
 	.lbs_ipc = sizeof(struct smack_known *),
 	.lbs_msg_msg = sizeof(struct smack_known *),
 	.lbs_superblock = sizeof(struct superblock_smack),
+	.lbs_xattr_count = SMACK_INODE_INIT_XATTRS,
 };
 
 static struct security_hook_list smack_hooks[] __ro_after_init = {
-- 
2.25.1

Re: [PATCH v12 1/4] security: Allow all LSMs to provide xattrs for inode_init_security hook

[Paul Moore]

On Jun 10, 2023 Roberto Sassu <roberto.sassu@huaweicloud.com> wrote:
> 
> Currently, the LSM infrastructure supports only one LSM providing an xattr
> and EVM calculating the HMAC on that xattr, plus other inode metadata.
> 
> Allow all LSMs to provide one or multiple xattrs, by extending the security
> blob reservation mechanism. Introduce the new lbs_xattr_count field of the
> lsm_blob_sizes structure, so that each LSM can specify how many xattrs it
> needs, and the LSM infrastructure knows how many xattr slots it should
> allocate.
> 
> Modify the inode_init_security hook definition, by passing the full
> xattr array allocated in security_inode_init_security(), and the current
> number of xattr slots in that array filled by LSMs. The first parameter
> would allow EVM to access and calculate the HMAC on xattrs supplied by
> other LSMs, the second to not leave gaps in the xattr array, when an LSM
> requested but did not provide xattrs (e.g. if it is not initialized).
> 
> Introduce lsm_get_xattr_slot(), which LSMs can call as many times as the
> number specified in the lbs_xattr_count field of the lsm_blob_sizes
> structure. During each call, lsm_get_xattr_slot() increments the number of
> filled xattrs, so that at the next invocation it returns the next xattr
> slot to fill.
> 
> Cleanup security_inode_init_security(). Unify the !initxattrs and
> initxattrs case by simply not allocating the new_xattrs array in the
> former. Update the documentation to reflect the changes, and fix the
> description of the xattr name, as it is not allocated anymore.
> 
> Adapt both SELinux and Smack to use the new definition of the
> inode_init_security hook, and to call lsm_get_xattr_slot() to obtain and
> fill the reserved slots in the xattr array.
> 
> Move the xattr->name assignment after the xattr->value one, so that it is
> done only in case of successful memory allocation.
> 
> Finally, change the default return value of the inode_init_security hook
> from zero to -EOPNOTSUPP, so that BPF LSM correctly follows the hook
> conventions.
> 
> Reported-by: Nicolas Bouchinet <nicolas.bouchinet@clip-os.org>
> Link: https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
>  include/linux/lsm_hook_defs.h |  6 +--
>  include/linux/lsm_hooks.h     | 20 ++++++++++
>  security/security.c           | 71 +++++++++++++++++++++++------------
>  security/selinux/hooks.c      | 17 +++++----
>  security/smack/smack_lsm.c    | 25 ++++++------
>  5 files changed, 92 insertions(+), 47 deletions(-)

Two *very* small suggestions below, but I can make those during the
merge if you are okay with that Roberto?

I'm also going to assume that Casey is okay with the Smack portion of
this patchset?  It looks fine to me, and considering his ACK on the
other Smack patch in this patchset I'm assuming he is okay with this
one as well ... ?

> diff --git a/security/security.c b/security/security.c
> index ee4f1cc4902..d5ef7df1ce4 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1591,11 +1592,15 @@ EXPORT_SYMBOL(security_dentry_create_files_as);
>   * created inode and set up the incore security field for the new inode.  This
>   * hook is called by the fs code as part of the inode creation transaction and
>   * provides for atomic labeling of the inode, unlike the post_create/mkdir/...
> - * hooks called by the VFS.  The hook function is expected to allocate the name
> - * and value via kmalloc, with the caller being responsible for calling kfree
> - * after using them.  If the security module does not use security attributes
> - * or does not wish to put a security attribute on this particular inode, then
> - * it should return -EOPNOTSUPP to skip this processing.
> + * hooks called by the VFS.  The hook function is expected to populate the
> + * @xattrs array, by calling lsm_get_xattr_slot() to retrieve the slots

I think we want to change "@xattrs array" to just "xattrs array" as
there is no function parameter named "xattrs" in the LSM/security_XXX
hook itself, just in the 'inode_init_security' hook implementation.

I might also break the new text describing the hook implementation
into a new paragraph.

> + * reserved by the security module with the lbs_xattr_count field of the
> + * lsm_blob_sizes structure.  For each slot, the hook function should set ->name
> + * to the attribute name suffix (e.g. selinux), to allocate ->value (will be
> + * freed by the caller) and set it to the attribute value, to set ->value_len to
> + * the length of the value.  If the security module does not use security
> + * attributes or does not wish to put a security attribute on this particular
> + * inode, then it should return -EOPNOTSUPP to skip this processing.
>   *
>   * Return: Returns 0 on success, -EOPNOTSUPP if no security attribute is
>   * needed, or -ENOMEM on memory allocation failure.
> @@ -1604,33 +1609,51 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
>  				 const struct qstr *qstr,
>  				 const initxattrs initxattrs, void *fs_data)
>  {
> -	struct xattr new_xattrs[MAX_LSM_EVM_XATTR + 1];
> -	struct xattr *lsm_xattr, *evm_xattr, *xattr;
> -	int ret;
> +	struct security_hook_list *P;

The above comments were nitpicky, this one is even more so ...
convention within security/security.c is to call the
security_hook_list pointer "hp", not "P" (although I recognize P is
used in the macro).

> +	struct xattr *new_xattrs = NULL;
> +	int ret = -EOPNOTSUPP, xattr_count = 0;

--
paul-moore.com

RE: [PATCH v12 1/4] security: Allow all LSMs to provide xattrs for inode_init_security hook

[Roberto Sassu]

> From: Paul Moore [mailto:paul@paul-moore.com]
> Sent: Friday, July 7, 2023 3:44 AM
> On Jun 10, 2023 Roberto Sassu <roberto.sassu@huaweicloud.com> wrote:
> >
> > Currently, the LSM infrastructure supports only one LSM providing an xattr
> > and EVM calculating the HMAC on that xattr, plus other inode metadata.
> >
> > Allow all LSMs to provide one or multiple xattrs, by extending the security
> > blob reservation mechanism. Introduce the new lbs_xattr_count field of the
> > lsm_blob_sizes structure, so that each LSM can specify how many xattrs it
> > needs, and the LSM infrastructure knows how many xattr slots it should
> > allocate.
> >
> > Modify the inode_init_security hook definition, by passing the full
> > xattr array allocated in security_inode_init_security(), and the current
> > number of xattr slots in that array filled by LSMs. The first parameter
> > would allow EVM to access and calculate the HMAC on xattrs supplied by
> > other LSMs, the second to not leave gaps in the xattr array, when an LSM
> > requested but did not provide xattrs (e.g. if it is not initialized).
> >
> > Introduce lsm_get_xattr_slot(), which LSMs can call as many times as the
> > number specified in the lbs_xattr_count field of the lsm_blob_sizes
> > structure. During each call, lsm_get_xattr_slot() increments the number of
> > filled xattrs, so that at the next invocation it returns the next xattr
> > slot to fill.
> >
> > Cleanup security_inode_init_security(). Unify the !initxattrs and
> > initxattrs case by simply not allocating the new_xattrs array in the
> > former. Update the documentation to reflect the changes, and fix the
> > description of the xattr name, as it is not allocated anymore.
> >
> > Adapt both SELinux and Smack to use the new definition of the
> > inode_init_security hook, and to call lsm_get_xattr_slot() to obtain and
> > fill the reserved slots in the xattr array.
> >
> > Move the xattr->name assignment after the xattr->value one, so that it is
> > done only in case of successful memory allocation.
> >
> > Finally, change the default return value of the inode_init_security hook
> > from zero to -EOPNOTSUPP, so that BPF LSM correctly follows the hook
> > conventions.
> >
> > Reported-by: Nicolas Bouchinet <nicolas.bouchinet@clip-os.org>
> > Link: https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/
> > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> > ---
> >  include/linux/lsm_hook_defs.h |  6 +--
> >  include/linux/lsm_hooks.h     | 20 ++++++++++
> >  security/security.c           | 71 +++++++++++++++++++++++------------
> >  security/selinux/hooks.c      | 17 +++++----
> >  security/smack/smack_lsm.c    | 25 ++++++------
> >  5 files changed, 92 insertions(+), 47 deletions(-)
> 
> Two *very* small suggestions below, but I can make those during the
> merge if you are okay with that Roberto?

Hi Paul

yes, sure, I'm ok with them. Please make them during the merge.

Thanks

Roberto

> I'm also going to assume that Casey is okay with the Smack portion of
> this patchset?  It looks fine to me, and considering his ACK on the
> other Smack patch in this patchset I'm assuming he is okay with this
> one as well ... ?
> 
> > diff --git a/security/security.c b/security/security.c
> > index ee4f1cc4902..d5ef7df1ce4 100644
> > --- a/security/security.c
> > +++ b/security/security.c
> > @@ -1591,11 +1592,15 @@ EXPORT_SYMBOL(security_dentry_create_files_as);
> >   * created inode and set up the incore security field for the new inode.  This
> >   * hook is called by the fs code as part of the inode creation transaction and
> >   * provides for atomic labeling of the inode, unlike the post_create/mkdir/...
> > - * hooks called by the VFS.  The hook function is expected to allocate the name
> > - * and value via kmalloc, with the caller being responsible for calling kfree
> > - * after using them.  If the security module does not use security attributes
> > - * or does not wish to put a security attribute on this particular inode, then
> > - * it should return -EOPNOTSUPP to skip this processing.
> > + * hooks called by the VFS.  The hook function is expected to populate the
> > + * @xattrs array, by calling lsm_get_xattr_slot() to retrieve the slots
> 
> I think we want to change "@xattrs array" to just "xattrs array" as
> there is no function parameter named "xattrs" in the LSM/security_XXX
> hook itself, just in the 'inode_init_security' hook implementation.
> 
> I might also break the new text describing the hook implementation
> into a new paragraph.
> 
> > + * reserved by the security module with the lbs_xattr_count field of the
> > + * lsm_blob_sizes structure.  For each slot, the hook function should set ->name
> > + * to the attribute name suffix (e.g. selinux), to allocate ->value (will be
> > + * freed by the caller) and set it to the attribute value, to set ->value_len to
> > + * the length of the value.  If the security module does not use security
> > + * attributes or does not wish to put a security attribute on this particular
> > + * inode, then it should return -EOPNOTSUPP to skip this processing.
> >   *
> >   * Return: Returns 0 on success, -EOPNOTSUPP if no security attribute is
> >   * needed, or -ENOMEM on memory allocation failure.
> > @@ -1604,33 +1609,51 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
> >  				 const struct qstr *qstr,
> >  				 const initxattrs initxattrs, void *fs_data)
> >  {
> > -	struct xattr new_xattrs[MAX_LSM_EVM_XATTR + 1];
> > -	struct xattr *lsm_xattr, *evm_xattr, *xattr;
> > -	int ret;
> > +	struct security_hook_list *P;
> 
> The above comments were nitpicky, this one is even more so ...
> convention within security/security.c is to call the
> security_hook_list pointer "hp", not "P" (although I recognize P is
> used in the macro).
> 
> > +	struct xattr *new_xattrs = NULL;
> > +	int ret = -EOPNOTSUPP, xattr_count = 0;
> 
> --
> paul-moore.com

Re: [PATCH v12 1/4] security: Allow all LSMs to provide xattrs for inode_init_security hook

[Paul Moore]

On Fri, Jul 7, 2023 at 2:49 AM Roberto Sassu <roberto.sassu@huawei.com> wrote:
> > From: Paul Moore [mailto:paul@paul-moore.com]
> > Sent: Friday, July 7, 2023 3:44 AM
> > On Jun 10, 2023 Roberto Sassu <roberto.sassu@huaweicloud.com> wrote:
> > >
> > > Currently, the LSM infrastructure supports only one LSM providing an xattr
> > > and EVM calculating the HMAC on that xattr, plus other inode metadata.
> > >
> > > Allow all LSMs to provide one or multiple xattrs, by extending the security
> > > blob reservation mechanism. Introduce the new lbs_xattr_count field of the
> > > lsm_blob_sizes structure, so that each LSM can specify how many xattrs it
> > > needs, and the LSM infrastructure knows how many xattr slots it should
> > > allocate.
> > >
> > > Modify the inode_init_security hook definition, by passing the full
> > > xattr array allocated in security_inode_init_security(), and the current
> > > number of xattr slots in that array filled by LSMs. The first parameter
> > > would allow EVM to access and calculate the HMAC on xattrs supplied by
> > > other LSMs, the second to not leave gaps in the xattr array, when an LSM
> > > requested but did not provide xattrs (e.g. if it is not initialized).
> > >
> > > Introduce lsm_get_xattr_slot(), which LSMs can call as many times as the
> > > number specified in the lbs_xattr_count field of the lsm_blob_sizes
> > > structure. During each call, lsm_get_xattr_slot() increments the number of
> > > filled xattrs, so that at the next invocation it returns the next xattr
> > > slot to fill.
> > >
> > > Cleanup security_inode_init_security(). Unify the !initxattrs and
> > > initxattrs case by simply not allocating the new_xattrs array in the
> > > former. Update the documentation to reflect the changes, and fix the
> > > description of the xattr name, as it is not allocated anymore.
> > >
> > > Adapt both SELinux and Smack to use the new definition of the
> > > inode_init_security hook, and to call lsm_get_xattr_slot() to obtain and
> > > fill the reserved slots in the xattr array.
> > >
> > > Move the xattr->name assignment after the xattr->value one, so that it is
> > > done only in case of successful memory allocation.
> > >
> > > Finally, change the default return value of the inode_init_security hook
> > > from zero to -EOPNOTSUPP, so that BPF LSM correctly follows the hook
> > > conventions.
> > >
> > > Reported-by: Nicolas Bouchinet <nicolas.bouchinet@clip-os.org>
> > > Link: https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/
> > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> > > ---
> > >  include/linux/lsm_hook_defs.h |  6 +--
> > >  include/linux/lsm_hooks.h     | 20 ++++++++++
> > >  security/security.c           | 71 +++++++++++++++++++++++------------
> > >  security/selinux/hooks.c      | 17 +++++----
> > >  security/smack/smack_lsm.c    | 25 ++++++------
> > >  5 files changed, 92 insertions(+), 47 deletions(-)
> >
> > Two *very* small suggestions below, but I can make those during the
> > merge if you are okay with that Roberto?
>
> Hi Paul
>
> yes, sure, I'm ok with them. Please make them during the merge.

Great, I'll queue this up for merging once the merge window closes.
I'll send confirmation once it's done but just a heads-up that things
might be a little delayed next week.

-- 
paul-moore.com

Re: [PATCH v12 1/4] security: Allow all LSMs to provide xattrs for inode_init_security hook

[Roberto Sassu]

On Fri, 2023-07-07 at 10:34 -0400, Paul Moore wrote:
> On Fri, Jul 7, 2023 at 2:49 AM Roberto Sassu <roberto.sassu@huawei.com> wrote:
> > > From: Paul Moore [mailto:paul@paul-moore.com]
> > > Sent: Friday, July 7, 2023 3:44 AM
> > > On Jun 10, 2023 Roberto Sassu <roberto.sassu@huaweicloud.com> wrote:
> > > > 
> > > > Currently, the LSM infrastructure supports only one LSM providing an xattr
> > > > and EVM calculating the HMAC on that xattr, plus other inode metadata.
> > > > 
> > > > Allow all LSMs to provide one or multiple xattrs, by extending the security
> > > > blob reservation mechanism. Introduce the new lbs_xattr_count field of the
> > > > lsm_blob_sizes structure, so that each LSM can specify how many xattrs it
> > > > needs, and the LSM infrastructure knows how many xattr slots it should
> > > > allocate.
> > > > 
> > > > Modify the inode_init_security hook definition, by passing the full
> > > > xattr array allocated in security_inode_init_security(), and the current
> > > > number of xattr slots in that array filled by LSMs. The first parameter
> > > > would allow EVM to access and calculate the HMAC on xattrs supplied by
> > > > other LSMs, the second to not leave gaps in the xattr array, when an LSM
> > > > requested but did not provide xattrs (e.g. if it is not initialized).
> > > > 
> > > > Introduce lsm_get_xattr_slot(), which LSMs can call as many times as the
> > > > number specified in the lbs_xattr_count field of the lsm_blob_sizes
> > > > structure. During each call, lsm_get_xattr_slot() increments the number of
> > > > filled xattrs, so that at the next invocation it returns the next xattr
> > > > slot to fill.
> > > > 
> > > > Cleanup security_inode_init_security(). Unify the !initxattrs and
> > > > initxattrs case by simply not allocating the new_xattrs array in the
> > > > former. Update the documentation to reflect the changes, and fix the
> > > > description of the xattr name, as it is not allocated anymore.
> > > > 
> > > > Adapt both SELinux and Smack to use the new definition of the
> > > > inode_init_security hook, and to call lsm_get_xattr_slot() to obtain and
> > > > fill the reserved slots in the xattr array.
> > > > 
> > > > Move the xattr->name assignment after the xattr->value one, so that it is
> > > > done only in case of successful memory allocation.
> > > > 
> > > > Finally, change the default return value of the inode_init_security hook
> > > > from zero to -EOPNOTSUPP, so that BPF LSM correctly follows the hook
> > > > conventions.
> > > > 
> > > > Reported-by: Nicolas Bouchinet <nicolas.bouchinet@clip-os.org>
> > > > Link: https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/
> > > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> > > > ---
> > > >  include/linux/lsm_hook_defs.h |  6 +--
> > > >  include/linux/lsm_hooks.h     | 20 ++++++++++
> > > >  security/security.c           | 71 +++++++++++++++++++++++------------
> > > >  security/selinux/hooks.c      | 17 +++++----
> > > >  security/smack/smack_lsm.c    | 25 ++++++------
> > > >  5 files changed, 92 insertions(+), 47 deletions(-)
> > > 
> > > Two *very* small suggestions below, but I can make those during the
> > > merge if you are okay with that Roberto?
> > 
> > Hi Paul
> > 
> > yes, sure, I'm ok with them. Please make them during the merge.
> 
> Great, I'll queue this up for merging once the merge window closes.
> I'll send confirmation once it's done but just a heads-up that things
> might be a little delayed next week.

Ok, no problem.

Thanks!

Roberto

Re: [PATCH v12 1/4] security: Allow all LSMs to provide xattrs for inode_init_security hook

[Casey Schaufler]

On 7/6/2023 6:43 PM, Paul Moore wrote:
> On Jun 10, 2023 Roberto Sassu <roberto.sassu@huaweicloud.com> wrote:
>> Currently, the LSM infrastructure supports only one LSM providing an xattr
>> and EVM calculating the HMAC on that xattr, plus other inode metadata.
>>
>> Allow all LSMs to provide one or multiple xattrs, by extending the security
>> blob reservation mechanism. Introduce the new lbs_xattr_count field of the
>> lsm_blob_sizes structure, so that each LSM can specify how many xattrs it
>> needs, and the LSM infrastructure knows how many xattr slots it should
>> allocate.
>>
>> Modify the inode_init_security hook definition, by passing the full
>> xattr array allocated in security_inode_init_security(), and the current
>> number of xattr slots in that array filled by LSMs. The first parameter
>> would allow EVM to access and calculate the HMAC on xattrs supplied by
>> other LSMs, the second to not leave gaps in the xattr array, when an LSM
>> requested but did not provide xattrs (e.g. if it is not initialized).
>>
>> Introduce lsm_get_xattr_slot(), which LSMs can call as many times as the
>> number specified in the lbs_xattr_count field of the lsm_blob_sizes
>> structure. During each call, lsm_get_xattr_slot() increments the number of
>> filled xattrs, so that at the next invocation it returns the next xattr
>> slot to fill.
>>
>> Cleanup security_inode_init_security(). Unify the !initxattrs and
>> initxattrs case by simply not allocating the new_xattrs array in the
>> former. Update the documentation to reflect the changes, and fix the
>> description of the xattr name, as it is not allocated anymore.
>>
>> Adapt both SELinux and Smack to use the new definition of the
>> inode_init_security hook, and to call lsm_get_xattr_slot() to obtain and
>> fill the reserved slots in the xattr array.
>>
>> Move the xattr->name assignment after the xattr->value one, so that it is
>> done only in case of successful memory allocation.
>>
>> Finally, change the default return value of the inode_init_security hook
>> from zero to -EOPNOTSUPP, so that BPF LSM correctly follows the hook
>> conventions.
>>
>> Reported-by: Nicolas Bouchinet <nicolas.bouchinet@clip-os.org>
>> Link: https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/
>> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
>> ---
>>  include/linux/lsm_hook_defs.h |  6 +--
>>  include/linux/lsm_hooks.h     | 20 ++++++++++
>>  security/security.c           | 71 +++++++++++++++++++++++------------
>>  security/selinux/hooks.c      | 17 +++++----
>>  security/smack/smack_lsm.c    | 25 ++++++------
>>  5 files changed, 92 insertions(+), 47 deletions(-)
> Two *very* small suggestions below, but I can make those during the
> merge if you are okay with that Roberto?
>
> I'm also going to assume that Casey is okay with the Smack portion of
> this patchset?  It looks fine to me, and considering his ACK on the
> other Smack patch in this patchset I'm assuming he is okay with this
> one as well ... ?

Yes, please feel free to add my Acked-by as needed.

>
>> diff --git a/security/security.c b/security/security.c
>> index ee4f1cc4902..d5ef7df1ce4 100644
>> --- a/security/security.c
>> +++ b/security/security.c
>> @@ -1591,11 +1592,15 @@ EXPORT_SYMBOL(security_dentry_create_files_as);
>>   * created inode and set up the incore security field for the new inode.  This
>>   * hook is called by the fs code as part of the inode creation transaction and
>>   * provides for atomic labeling of the inode, unlike the post_create/mkdir/...
>> - * hooks called by the VFS.  The hook function is expected to allocate the name
>> - * and value via kmalloc, with the caller being responsible for calling kfree
>> - * after using them.  If the security module does not use security attributes
>> - * or does not wish to put a security attribute on this particular inode, then
>> - * it should return -EOPNOTSUPP to skip this processing.
>> + * hooks called by the VFS.  The hook function is expected to populate the
>> + * @xattrs array, by calling lsm_get_xattr_slot() to retrieve the slots
> I think we want to change "@xattrs array" to just "xattrs array" as
> there is no function parameter named "xattrs" in the LSM/security_XXX
> hook itself, just in the 'inode_init_security' hook implementation.
>
> I might also break the new text describing the hook implementation
> into a new paragraph.
>
>> + * reserved by the security module with the lbs_xattr_count field of the
>> + * lsm_blob_sizes structure.  For each slot, the hook function should set ->name
>> + * to the attribute name suffix (e.g. selinux), to allocate ->value (will be
>> + * freed by the caller) and set it to the attribute value, to set ->value_len to
>> + * the length of the value.  If the security module does not use security
>> + * attributes or does not wish to put a security attribute on this particular
>> + * inode, then it should return -EOPNOTSUPP to skip this processing.
>>   *
>>   * Return: Returns 0 on success, -EOPNOTSUPP if no security attribute is
>>   * needed, or -ENOMEM on memory allocation failure.
>> @@ -1604,33 +1609,51 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
>>  				 const struct qstr *qstr,
>>  				 const initxattrs initxattrs, void *fs_data)
>>  {
>> -	struct xattr new_xattrs[MAX_LSM_EVM_XATTR + 1];
>> -	struct xattr *lsm_xattr, *evm_xattr, *xattr;
>> -	int ret;
>> +	struct security_hook_list *P;
> The above comments were nitpicky, this one is even more so ...
> convention within security/security.c is to call the
> security_hook_list pointer "hp", not "P" (although I recognize P is
> used in the macro).
>
>> +	struct xattr *new_xattrs = NULL;
>> +	int ret = -EOPNOTSUPP, xattr_count = 0;
> --
> paul-moore.com

Re: [PATCH v12 1/4] security: Allow all LSMs to provide xattrs for inode_init_security hook

[Paul Moore]

On Fri, Jul 7, 2023 at 12:54 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> On 7/6/2023 6:43 PM, Paul Moore wrote:
> > On Jun 10, 2023 Roberto Sassu <roberto.sassu@huaweicloud.com> wrote:
> >> Currently, the LSM infrastructure supports only one LSM providing an xattr
> >> and EVM calculating the HMAC on that xattr, plus other inode metadata.
> >>
> >> Allow all LSMs to provide one or multiple xattrs, by extending the security
> >> blob reservation mechanism. Introduce the new lbs_xattr_count field of the
> >> lsm_blob_sizes structure, so that each LSM can specify how many xattrs it
> >> needs, and the LSM infrastructure knows how many xattr slots it should
> >> allocate.
> >>
> >> Modify the inode_init_security hook definition, by passing the full
> >> xattr array allocated in security_inode_init_security(), and the current
> >> number of xattr slots in that array filled by LSMs. The first parameter
> >> would allow EVM to access and calculate the HMAC on xattrs supplied by
> >> other LSMs, the second to not leave gaps in the xattr array, when an LSM
> >> requested but did not provide xattrs (e.g. if it is not initialized).
> >>
> >> Introduce lsm_get_xattr_slot(), which LSMs can call as many times as the
> >> number specified in the lbs_xattr_count field of the lsm_blob_sizes
> >> structure. During each call, lsm_get_xattr_slot() increments the number of
> >> filled xattrs, so that at the next invocation it returns the next xattr
> >> slot to fill.
> >>
> >> Cleanup security_inode_init_security(). Unify the !initxattrs and
> >> initxattrs case by simply not allocating the new_xattrs array in the
> >> former. Update the documentation to reflect the changes, and fix the
> >> description of the xattr name, as it is not allocated anymore.
> >>
> >> Adapt both SELinux and Smack to use the new definition of the
> >> inode_init_security hook, and to call lsm_get_xattr_slot() to obtain and
> >> fill the reserved slots in the xattr array.
> >>
> >> Move the xattr->name assignment after the xattr->value one, so that it is
> >> done only in case of successful memory allocation.
> >>
> >> Finally, change the default return value of the inode_init_security hook
> >> from zero to -EOPNOTSUPP, so that BPF LSM correctly follows the hook
> >> conventions.
> >>
> >> Reported-by: Nicolas Bouchinet <nicolas.bouchinet@clip-os.org>
> >> Link: https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/
> >> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> >> ---
> >>  include/linux/lsm_hook_defs.h |  6 +--
> >>  include/linux/lsm_hooks.h     | 20 ++++++++++
> >>  security/security.c           | 71 +++++++++++++++++++++++------------
> >>  security/selinux/hooks.c      | 17 +++++----
> >>  security/smack/smack_lsm.c    | 25 ++++++------
> >>  5 files changed, 92 insertions(+), 47 deletions(-)
> > Two *very* small suggestions below, but I can make those during the
> > merge if you are okay with that Roberto?
> >
> > I'm also going to assume that Casey is okay with the Smack portion of
> > this patchset?  It looks fine to me, and considering his ACK on the
> > other Smack patch in this patchset I'm assuming he is okay with this
> > one as well ... ?
>
> Yes, please feel free to add my Acked-by as needed.

Done.  Thanks Casey.

-- 
paul-moore.com

Re: [PATCH v12 1/4] security: Allow all LSMs to provide xattrs for inode_init_security hook

[Paul Moore]

On Fri, Jul 7, 2023 at 5:44 PM Paul Moore <paul@paul-moore.com> wrote:
> On Fri, Jul 7, 2023 at 12:54 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> > On 7/6/2023 6:43 PM, Paul Moore wrote:
> > > On Jun 10, 2023 Roberto Sassu <roberto.sassu@huaweicloud.com> wrote:
> > >> Currently, the LSM infrastructure supports only one LSM providing an xattr
> > >> and EVM calculating the HMAC on that xattr, plus other inode metadata.
> > >>
> > >> Allow all LSMs to provide one or multiple xattrs, by extending the security
> > >> blob reservation mechanism. Introduce the new lbs_xattr_count field of the
> > >> lsm_blob_sizes structure, so that each LSM can specify how many xattrs it
> > >> needs, and the LSM infrastructure knows how many xattr slots it should
> > >> allocate.
> > >>
> > >> Modify the inode_init_security hook definition, by passing the full
> > >> xattr array allocated in security_inode_init_security(), and the current
> > >> number of xattr slots in that array filled by LSMs. The first parameter
> > >> would allow EVM to access and calculate the HMAC on xattrs supplied by
> > >> other LSMs, the second to not leave gaps in the xattr array, when an LSM
> > >> requested but did not provide xattrs (e.g. if it is not initialized).
> > >>
> > >> Introduce lsm_get_xattr_slot(), which LSMs can call as many times as the
> > >> number specified in the lbs_xattr_count field of the lsm_blob_sizes
> > >> structure. During each call, lsm_get_xattr_slot() increments the number of
> > >> filled xattrs, so that at the next invocation it returns the next xattr
> > >> slot to fill.
> > >>
> > >> Cleanup security_inode_init_security(). Unify the !initxattrs and
> > >> initxattrs case by simply not allocating the new_xattrs array in the
> > >> former. Update the documentation to reflect the changes, and fix the
> > >> description of the xattr name, as it is not allocated anymore.
> > >>
> > >> Adapt both SELinux and Smack to use the new definition of the
> > >> inode_init_security hook, and to call lsm_get_xattr_slot() to obtain and
> > >> fill the reserved slots in the xattr array.
> > >>
> > >> Move the xattr->name assignment after the xattr->value one, so that it is
> > >> done only in case of successful memory allocation.
> > >>
> > >> Finally, change the default return value of the inode_init_security hook
> > >> from zero to -EOPNOTSUPP, so that BPF LSM correctly follows the hook
> > >> conventions.
> > >>
> > >> Reported-by: Nicolas Bouchinet <nicolas.bouchinet@clip-os.org>
> > >> Link: https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/
> > >> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> > >> ---
> > >>  include/linux/lsm_hook_defs.h |  6 +--
> > >>  include/linux/lsm_hooks.h     | 20 ++++++++++
> > >>  security/security.c           | 71 +++++++++++++++++++++++------------
> > >>  security/selinux/hooks.c      | 17 +++++----
> > >>  security/smack/smack_lsm.c    | 25 ++++++------
> > >>  5 files changed, 92 insertions(+), 47 deletions(-)
> > > Two *very* small suggestions below, but I can make those during the
> > > merge if you are okay with that Roberto?
> > >
> > > I'm also going to assume that Casey is okay with the Smack portion of
> > > this patchset?  It looks fine to me, and considering his ACK on the
> > > other Smack patch in this patchset I'm assuming he is okay with this
> > > one as well ... ?
> >
> > Yes, please feel free to add my Acked-by as needed.
>
> Done.  Thanks Casey.

I'm merging the full patchset into lsm/next right now.  Thanks for all
your work on this Roberto, and a thank you for everyone else who
helped with reviews, testing, etc.

-- 
paul-moore.com

Re: [PATCH v12 1/4] security: Allow all LSMs to provide xattrs for inode_init_security hook

[Roberto Sassu]

On Mon, 2023-07-10 at 14:04 -0400, Paul Moore wrote:
> On Fri, Jul 7, 2023 at 5:44 PM Paul Moore <paul@paul-moore.com> wrote:
> > On Fri, Jul 7, 2023 at 12:54 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> > > On 7/6/2023 6:43 PM, Paul Moore wrote:
> > > > On Jun 10, 2023 Roberto Sassu <roberto.sassu@huaweicloud.com> wrote:
> > > > > Currently, the LSM infrastructure supports only one LSM providing an xattr
> > > > > and EVM calculating the HMAC on that xattr, plus other inode metadata.
> > > > > 
> > > > > Allow all LSMs to provide one or multiple xattrs, by extending the security
> > > > > blob reservation mechanism. Introduce the new lbs_xattr_count field of the
> > > > > lsm_blob_sizes structure, so that each LSM can specify how many xattrs it
> > > > > needs, and the LSM infrastructure knows how many xattr slots it should
> > > > > allocate.
> > > > > 
> > > > > Modify the inode_init_security hook definition, by passing the full
> > > > > xattr array allocated in security_inode_init_security(), and the current
> > > > > number of xattr slots in that array filled by LSMs. The first parameter
> > > > > would allow EVM to access and calculate the HMAC on xattrs supplied by
> > > > > other LSMs, the second to not leave gaps in the xattr array, when an LSM
> > > > > requested but did not provide xattrs (e.g. if it is not initialized).
> > > > > 
> > > > > Introduce lsm_get_xattr_slot(), which LSMs can call as many times as the
> > > > > number specified in the lbs_xattr_count field of the lsm_blob_sizes
> > > > > structure. During each call, lsm_get_xattr_slot() increments the number of
> > > > > filled xattrs, so that at the next invocation it returns the next xattr
> > > > > slot to fill.
> > > > > 
> > > > > Cleanup security_inode_init_security(). Unify the !initxattrs and
> > > > > initxattrs case by simply not allocating the new_xattrs array in the
> > > > > former. Update the documentation to reflect the changes, and fix the
> > > > > description of the xattr name, as it is not allocated anymore.
> > > > > 
> > > > > Adapt both SELinux and Smack to use the new definition of the
> > > > > inode_init_security hook, and to call lsm_get_xattr_slot() to obtain and
> > > > > fill the reserved slots in the xattr array.
> > > > > 
> > > > > Move the xattr->name assignment after the xattr->value one, so that it is
> > > > > done only in case of successful memory allocation.
> > > > > 
> > > > > Finally, change the default return value of the inode_init_security hook
> > > > > from zero to -EOPNOTSUPP, so that BPF LSM correctly follows the hook
> > > > > conventions.
> > > > > 
> > > > > Reported-by: Nicolas Bouchinet <nicolas.bouchinet@clip-os.org>
> > > > > Link: https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/
> > > > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> > > > > ---
> > > > >  include/linux/lsm_hook_defs.h |  6 +--
> > > > >  include/linux/lsm_hooks.h     | 20 ++++++++++
> > > > >  security/security.c           | 71 +++++++++++++++++++++++------------
> > > > >  security/selinux/hooks.c      | 17 +++++----
> > > > >  security/smack/smack_lsm.c    | 25 ++++++------
> > > > >  5 files changed, 92 insertions(+), 47 deletions(-)
> > > > Two *very* small suggestions below, but I can make those during the
> > > > merge if you are okay with that Roberto?
> > > > 
> > > > I'm also going to assume that Casey is okay with the Smack portion of
> > > > this patchset?  It looks fine to me, and considering his ACK on the
> > > > other Smack patch in this patchset I'm assuming he is okay with this
> > > > one as well ... ?
> > > 
> > > Yes, please feel free to add my Acked-by as needed.
> > 
> > Done.  Thanks Casey.
> 
> I'm merging the full patchset into lsm/next right now.  Thanks for all
> your work on this Roberto, and a thank you for everyone else who
> helped with reviews, testing, etc.

Thanks Paul, also for making the patch set better!

Roberto

[PATCH v12 2/4] smack: Set the SMACK64TRANSMUTE xattr in smack_inode_init_security()

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu@huawei.com>

With the newly added ability of LSMs to supply multiple xattrs, set
SMACK64TRASMUTE in smack_inode_init_security(), instead of d_instantiate().
Do it by incrementing SMACK_INODE_INIT_XATTRS to 2 and by calling
lsm_get_xattr_slot() a second time, if the transmuting conditions are met.

The LSM infrastructure passes all xattrs provided by LSMs to the
filesystems through the initxattrs() callback, so that filesystems can
store xattrs in the disk.

After the change, the SMK_INODE_TRANSMUTE inode flag is always set by
d_instantiate() after fetching SMACK64TRANSMUTE from the disk. Before it
was done by smack_inode_post_setxattr() as result of the __vfs_setxattr()
call.

Removing __vfs_setxattr() also prevents invalidating the EVM HMAC, by
adding a new xattr without checking and updating the existing HMAC.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
 security/smack/smack.h     |  2 +-
 security/smack/smack_lsm.c | 45 ++++++++++++++++++++++++--------------
 2 files changed, 29 insertions(+), 18 deletions(-)

diff --git a/security/smack/smack.h b/security/smack/smack.h
index aa15ff56ed6..041688e5a77 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -128,7 +128,7 @@ struct task_smack {
 
 #define	SMK_INODE_INSTANT	0x01	/* inode is instantiated */
 #define	SMK_INODE_TRANSMUTE	0x02	/* directory is transmuting */
-#define	SMK_INODE_CHANGED	0x04	/* smack was transmuted */
+#define	SMK_INODE_CHANGED	0x04	/* smack was transmuted (unused) */
 #define	SMK_INODE_IMPURE	0x08	/* involved in an impure transaction */
 
 /*
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 25ade3819af..679156601a1 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -52,7 +52,14 @@
 #define SMK_RECEIVING	1
 #define SMK_SENDING	2
 
-#define SMACK_INODE_INIT_XATTRS 1
+/*
+ * Smack uses multiple xattrs.
+ * SMACK64 - for access control,
+ * SMACK64TRANSMUTE - label initialization,
+ * Not saved on files - SMACK64IPIN and SMACK64IPOUT,
+ * Must be set explicitly - SMACK64EXEC and SMACK64MMAP
+ */
+#define SMACK_INODE_INIT_XATTRS 2
 
 #ifdef SMACK_IPV6_PORT_LABELING
 static DEFINE_MUTEX(smack_ipv6_lock);
@@ -935,7 +942,6 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
 				     struct xattr *xattrs, int *xattr_count)
 {
 	struct task_smack *tsp = smack_cred(current_cred());
-	struct inode_smack *issp = smack_inode(inode);
 	struct smack_known *skp = smk_of_task(tsp);
 	struct smack_known *isp = smk_of_inode(inode);
 	struct smack_known *dsp = smk_of_inode(dir);
@@ -963,6 +969,8 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
 		if ((tsp->smk_task == tsp->smk_transmuted) ||
 		    (may > 0 && ((may & MAY_TRANSMUTE) != 0) &&
 		     smk_inode_transmutable(dir))) {
+			struct xattr *xattr_transmute;
+
 			/*
 			 * The caller of smack_dentry_create_files_as()
 			 * should have overridden the current cred, so the
@@ -971,7 +979,18 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
 			 */
 			if (tsp->smk_task != tsp->smk_transmuted)
 				isp = dsp;
-			issp->smk_flags |= SMK_INODE_CHANGED;
+			xattr_transmute = lsm_get_xattr_slot(xattrs,
+							     xattr_count);
+			if (xattr_transmute) {
+				xattr_transmute->value = kmemdup(TRANS_TRUE,
+								 TRANS_TRUE_SIZE,
+								 GFP_NOFS);
+				if (!xattr_transmute->value)
+					return -ENOMEM;
+
+				xattr_transmute->value_len = TRANS_TRUE_SIZE;
+				xattr_transmute->name = XATTR_SMACK_TRANSMUTE;
+			}
 		}
 
 		xattr->value = kstrdup(isp->smk_known, GFP_NOFS);
@@ -3518,20 +3537,12 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode)
 			 * If there is a transmute attribute on the
 			 * directory mark the inode.
 			 */
-			if (isp->smk_flags & SMK_INODE_CHANGED) {
-				isp->smk_flags &= ~SMK_INODE_CHANGED;
-				rc = __vfs_setxattr(&nop_mnt_idmap, dp, inode,
-					XATTR_NAME_SMACKTRANSMUTE,
-					TRANS_TRUE, TRANS_TRUE_SIZE,
-					0);
-			} else {
-				rc = __vfs_getxattr(dp, inode,
-					XATTR_NAME_SMACKTRANSMUTE, trattr,
-					TRANS_TRUE_SIZE);
-				if (rc >= 0 && strncmp(trattr, TRANS_TRUE,
-						       TRANS_TRUE_SIZE) != 0)
-					rc = -EINVAL;
-			}
+			rc = __vfs_getxattr(dp, inode,
+					    XATTR_NAME_SMACKTRANSMUTE, trattr,
+					    TRANS_TRUE_SIZE);
+			if (rc >= 0 && strncmp(trattr, TRANS_TRUE,
+					       TRANS_TRUE_SIZE) != 0)
+				rc = -EINVAL;
 			if (rc >= 0)
 				transflag = SMK_INODE_TRANSMUTE;
 		}
-- 
2.25.1

Re: [PATCH v12 2/4] smack: Set the SMACK64TRANSMUTE xattr in smack_inode_init_security()

[Casey Schaufler]

On 6/10/2023 12:57 AM, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
>
> With the newly added ability of LSMs to supply multiple xattrs, set
> SMACK64TRASMUTE in smack_inode_init_security(), instead of d_instantiate().
> Do it by incrementing SMACK_INODE_INIT_XATTRS to 2 and by calling
> lsm_get_xattr_slot() a second time, if the transmuting conditions are met.
>
> The LSM infrastructure passes all xattrs provided by LSMs to the
> filesystems through the initxattrs() callback, so that filesystems can
> store xattrs in the disk.
>
> After the change, the SMK_INODE_TRANSMUTE inode flag is always set by
> d_instantiate() after fetching SMACK64TRANSMUTE from the disk. Before it
> was done by smack_inode_post_setxattr() as result of the __vfs_setxattr()
> call.
>
> Removing __vfs_setxattr() also prevents invalidating the EVM HMAC, by
> adding a new xattr without checking and updating the existing HMAC.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>

Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>

> ---
>  security/smack/smack.h     |  2 +-
>  security/smack/smack_lsm.c | 45 ++++++++++++++++++++++++--------------
>  2 files changed, 29 insertions(+), 18 deletions(-)
>
> diff --git a/security/smack/smack.h b/security/smack/smack.h
> index aa15ff56ed6..041688e5a77 100644
> --- a/security/smack/smack.h
> +++ b/security/smack/smack.h
> @@ -128,7 +128,7 @@ struct task_smack {
>  
>  #define	SMK_INODE_INSTANT	0x01	/* inode is instantiated */
>  #define	SMK_INODE_TRANSMUTE	0x02	/* directory is transmuting */
> -#define	SMK_INODE_CHANGED	0x04	/* smack was transmuted */
> +#define	SMK_INODE_CHANGED	0x04	/* smack was transmuted (unused) */
>  #define	SMK_INODE_IMPURE	0x08	/* involved in an impure transaction */
>  
>  /*
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 25ade3819af..679156601a1 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -52,7 +52,14 @@
>  #define SMK_RECEIVING	1
>  #define SMK_SENDING	2
>  
> -#define SMACK_INODE_INIT_XATTRS 1
> +/*
> + * Smack uses multiple xattrs.
> + * SMACK64 - for access control,
> + * SMACK64TRANSMUTE - label initialization,
> + * Not saved on files - SMACK64IPIN and SMACK64IPOUT,
> + * Must be set explicitly - SMACK64EXEC and SMACK64MMAP
> + */
> +#define SMACK_INODE_INIT_XATTRS 2
>  
>  #ifdef SMACK_IPV6_PORT_LABELING
>  static DEFINE_MUTEX(smack_ipv6_lock);
> @@ -935,7 +942,6 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
>  				     struct xattr *xattrs, int *xattr_count)
>  {
>  	struct task_smack *tsp = smack_cred(current_cred());
> -	struct inode_smack *issp = smack_inode(inode);
>  	struct smack_known *skp = smk_of_task(tsp);
>  	struct smack_known *isp = smk_of_inode(inode);
>  	struct smack_known *dsp = smk_of_inode(dir);
> @@ -963,6 +969,8 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
>  		if ((tsp->smk_task == tsp->smk_transmuted) ||
>  		    (may > 0 && ((may & MAY_TRANSMUTE) != 0) &&
>  		     smk_inode_transmutable(dir))) {
> +			struct xattr *xattr_transmute;
> +
>  			/*
>  			 * The caller of smack_dentry_create_files_as()
>  			 * should have overridden the current cred, so the
> @@ -971,7 +979,18 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
>  			 */
>  			if (tsp->smk_task != tsp->smk_transmuted)
>  				isp = dsp;
> -			issp->smk_flags |= SMK_INODE_CHANGED;
> +			xattr_transmute = lsm_get_xattr_slot(xattrs,
> +							     xattr_count);
> +			if (xattr_transmute) {
> +				xattr_transmute->value = kmemdup(TRANS_TRUE,
> +								 TRANS_TRUE_SIZE,
> +								 GFP_NOFS);
> +				if (!xattr_transmute->value)
> +					return -ENOMEM;
> +
> +				xattr_transmute->value_len = TRANS_TRUE_SIZE;
> +				xattr_transmute->name = XATTR_SMACK_TRANSMUTE;
> +			}
>  		}
>  
>  		xattr->value = kstrdup(isp->smk_known, GFP_NOFS);
> @@ -3518,20 +3537,12 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode)
>  			 * If there is a transmute attribute on the
>  			 * directory mark the inode.
>  			 */
> -			if (isp->smk_flags & SMK_INODE_CHANGED) {
> -				isp->smk_flags &= ~SMK_INODE_CHANGED;
> -				rc = __vfs_setxattr(&nop_mnt_idmap, dp, inode,
> -					XATTR_NAME_SMACKTRANSMUTE,
> -					TRANS_TRUE, TRANS_TRUE_SIZE,
> -					0);
> -			} else {
> -				rc = __vfs_getxattr(dp, inode,
> -					XATTR_NAME_SMACKTRANSMUTE, trattr,
> -					TRANS_TRUE_SIZE);
> -				if (rc >= 0 && strncmp(trattr, TRANS_TRUE,
> -						       TRANS_TRUE_SIZE) != 0)
> -					rc = -EINVAL;
> -			}
> +			rc = __vfs_getxattr(dp, inode,
> +					    XATTR_NAME_SMACKTRANSMUTE, trattr,
> +					    TRANS_TRUE_SIZE);
> +			if (rc >= 0 && strncmp(trattr, TRANS_TRUE,
> +					       TRANS_TRUE_SIZE) != 0)
> +				rc = -EINVAL;
>  			if (rc >= 0)
>  				transflag = SMK_INODE_TRANSMUTE;
>  		}

[PATCH v12 3/4] evm: Align evm_inode_init_security() definition with LSM infrastructure

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu@huawei.com>

Change the evm_inode_init_security() definition to align with the LSM
infrastructure. Keep the existing behavior of including in the HMAC
calculation only the first xattr provided by LSMs.

Changing the evm_inode_init_security() definition requires passing the
xattr array allocated by security_inode_init_security(), and the number of
xattrs filled by previously invoked LSMs.

Use the newly introduced lsm_get_xattr_slot() to position EVM correctly in
the xattrs array, like a regular LSM, and to increment the number of filled
slots. For now, the LSM infrastructure allocates enough xattrs slots to
store the EVM xattr, without using the reservation mechanism.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
---
 include/linux/evm.h               | 14 ++++++++------
 security/integrity/evm/evm_main.c | 16 ++++++++++------
 security/security.c               |  4 ++--
 3 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/include/linux/evm.h b/include/linux/evm.h
index 7dc1ee74169..01fc495a83e 100644
--- a/include/linux/evm.h
+++ b/include/linux/evm.h
@@ -56,9 +56,10 @@ static inline void evm_inode_post_set_acl(struct dentry *dentry,
 {
 	return evm_inode_post_setxattr(dentry, acl_name, NULL, 0);
 }
-extern int evm_inode_init_security(struct inode *inode,
-				   const struct xattr *xattr_array,
-				   struct xattr *evm);
+
+int evm_inode_init_security(struct inode *inode, struct inode *dir,
+			    const struct qstr *qstr, struct xattr *xattrs,
+			    int *xattr_count);
 extern bool evm_revalidate_status(const char *xattr_name);
 extern int evm_protected_xattr_if_enabled(const char *req_xattr_name);
 extern int evm_read_protected_xattrs(struct dentry *dentry, u8 *buffer,
@@ -157,9 +158,10 @@ static inline void evm_inode_post_set_acl(struct dentry *dentry,
 	return;
 }
 
-static inline int evm_inode_init_security(struct inode *inode,
-					  const struct xattr *xattr_array,
-					  struct xattr *evm)
+static inline int evm_inode_init_security(struct inode *inode, struct inode *dir,
+					  const struct qstr *qstr,
+					  struct xattr *xattrs,
+					  int *xattr_count)
 {
 	return 0;
 }
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index cf24c525558..475196ce712 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -21,6 +21,7 @@
 #include <linux/evm.h>
 #include <linux/magic.h>
 #include <linux/posix_acl_xattr.h>
+#include <linux/lsm_hooks.h>
 
 #include <crypto/hash.h>
 #include <crypto/hash_info.h>
@@ -864,23 +865,26 @@ void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
 /*
  * evm_inode_init_security - initializes security.evm HMAC value
  */
-int evm_inode_init_security(struct inode *inode,
-				 const struct xattr *lsm_xattr,
-				 struct xattr *evm_xattr)
+int evm_inode_init_security(struct inode *inode, struct inode *dir,
+			    const struct qstr *qstr, struct xattr *xattrs,
+			    int *xattr_count)
 {
 	struct evm_xattr *xattr_data;
+	struct xattr *evm_xattr;
 	int rc;
 
-	if (!(evm_initialized & EVM_INIT_HMAC) ||
-	    !evm_protected_xattr(lsm_xattr->name))
+	if (!(evm_initialized & EVM_INIT_HMAC) || !xattrs ||
+	    !evm_protected_xattr(xattrs->name))
 		return 0;
 
+	evm_xattr = lsm_get_xattr_slot(xattrs, xattr_count);
+
 	xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
 	if (!xattr_data)
 		return -ENOMEM;
 
 	xattr_data->data.type = EVM_XATTR_HMAC;
-	rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
+	rc = evm_init_hmac(inode, xattrs, xattr_data->digest);
 	if (rc < 0)
 		goto out;
 
diff --git a/security/security.c b/security/security.c
index d5ef7df1ce4..819294d91ad 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1645,8 +1645,8 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
 	if (!xattr_count)
 		goto out;
 
-	ret = evm_inode_init_security(inode, new_xattrs,
-				      &new_xattrs[xattr_count]);
+	ret = evm_inode_init_security(inode, dir, qstr, new_xattrs,
+				      &xattr_count);
 	if (ret)
 		goto out;
 	ret = initxattrs(inode, new_xattrs, fs_data);
-- 
2.25.1

Re: [PATCH v12 3/4] evm: Align evm_inode_init_security() definition with LSM infrastructure

[Mimi Zohar]

On Sat, 2023-06-10 at 09:57 +0200, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
> 
> Change the evm_inode_init_security() definition to align with the LSM
> infrastructure. Keep the existing behavior of including in the HMAC
> calculation only the first xattr provided by LSMs.
> 
> Changing the evm_inode_init_security() definition requires passing the
> xattr array allocated by security_inode_init_security(), and the number of
> xattrs filled by previously invoked LSMs.
> 
> Use the newly introduced lsm_get_xattr_slot() to position EVM correctly in
> the xattrs array, like a regular LSM, and to increment the number of filled
> slots. For now, the LSM infrastructure allocates enough xattrs slots to
> store the EVM xattr, without using the reservation mechanism.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>

Thanks, Roberto!

Acked-by: Mimi Zohar <zohar@linux.ibm.com>

[PATCH v12 4/4] evm: Support multiple LSMs providing an xattr

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu@huawei.com>

Currently, evm_inode_init_security() processes a single LSM xattr from the
array passed by security_inode_init_security(), and calculates the HMAC on
it and other inode metadata.

As the LSM infrastructure now can pass to EVM an array with multiple
xattrs, scan them until the terminator (xattr name NULL), and calculate the
HMAC on all of them.

Also, double check that the xattrs array terminator is the first non-filled
slot (obtained with lsm_get_xattr_slot()). Consumers of the xattrs array,
such as the initxattrs() callbacks, rely on the terminator.

Finally, change the name of the lsm_xattr parameter of evm_init_hmac() to
xattrs, to reflect the new type of information passed.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
---
 security/integrity/evm/evm.h        |  4 +++-
 security/integrity/evm/evm_crypto.c | 11 +++++++++--
 security/integrity/evm/evm_main.c   | 29 +++++++++++++++++++++++++----
 3 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h
index f8b8c5004fc..53bd7fec93f 100644
--- a/security/integrity/evm/evm.h
+++ b/security/integrity/evm/evm.h
@@ -46,6 +46,8 @@ struct evm_digest {
 	char digest[IMA_MAX_DIGEST_SIZE];
 } __packed;
 
+int evm_protected_xattr(const char *req_xattr_name);
+
 int evm_init_key(void);
 int evm_update_evmxattr(struct dentry *dentry,
 			const char *req_xattr_name,
@@ -58,7 +60,7 @@ int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
 		  const char *req_xattr_value,
 		  size_t req_xattr_value_len, char type,
 		  struct evm_digest *data);
-int evm_init_hmac(struct inode *inode, const struct xattr *xattr,
+int evm_init_hmac(struct inode *inode, const struct xattr *xattrs,
 		  char *hmac_val);
 int evm_init_secfs(void);
 
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index 033804f5a5f..eb6b9f0a5e9 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -385,10 +385,11 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
 	return rc;
 }
 
-int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
+int evm_init_hmac(struct inode *inode, const struct xattr *xattrs,
 		  char *hmac_val)
 {
 	struct shash_desc *desc;
+	const struct xattr *xattr;
 
 	desc = init_desc(EVM_XATTR_HMAC, HASH_ALGO_SHA1);
 	if (IS_ERR(desc)) {
@@ -396,7 +397,13 @@ int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
 		return PTR_ERR(desc);
 	}
 
-	crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
+	for (xattr = xattrs; xattr->name; xattr++) {
+		if (!evm_protected_xattr(xattr->name))
+			continue;
+
+		crypto_shash_update(desc, xattr->value, xattr->value_len);
+	}
+
 	hmac_add_misc(desc, inode, EVM_XATTR_HMAC, hmac_val);
 	kfree(desc);
 	return 0;
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 475196ce712..7c6c9064ff5 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -306,7 +306,7 @@ static int evm_protected_xattr_common(const char *req_xattr_name,
 	return found;
 }
 
-static int evm_protected_xattr(const char *req_xattr_name)
+int evm_protected_xattr(const char *req_xattr_name)
 {
 	return evm_protected_xattr_common(req_xattr_name, false);
 }
@@ -870,14 +870,35 @@ int evm_inode_init_security(struct inode *inode, struct inode *dir,
 			    int *xattr_count)
 {
 	struct evm_xattr *xattr_data;
-	struct xattr *evm_xattr;
+	struct xattr *xattr, *evm_xattr;
+	bool evm_protected_xattrs = false;
 	int rc;
 
-	if (!(evm_initialized & EVM_INIT_HMAC) || !xattrs ||
-	    !evm_protected_xattr(xattrs->name))
+	if (!(evm_initialized & EVM_INIT_HMAC) || !xattrs)
+		return 0;
+
+	/*
+	 * security_inode_init_security() makes sure that the xattrs array is
+	 * contiguous, there is enough space for security.evm, and that there is
+	 * a terminator at the end of the array.
+	 */
+	for (xattr = xattrs; xattr->name; xattr++) {
+		if (evm_protected_xattr(xattr->name))
+			evm_protected_xattrs = true;
+	}
+
+	/* EVM xattr not needed. */
+	if (!evm_protected_xattrs)
 		return 0;
 
 	evm_xattr = lsm_get_xattr_slot(xattrs, xattr_count);
+	/*
+	 * Array terminator (xattr name = NULL) must be the first non-filled
+	 * xattr slot.
+	 */
+	WARN_ONCE(evm_xattr != xattr,
+		  "%s: xattrs terminator is not the first non-filled slot\n",
+		  __func__);
 
 	xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
 	if (!xattr_data)
-- 
2.25.1

Re: [PATCH v12 4/4] evm: Support multiple LSMs providing an xattr

[Mimi Zohar]

On Sat, 2023-06-10 at 09:57 +0200, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
> 
> Currently, evm_inode_init_security() processes a single LSM xattr from the
> array passed by security_inode_init_security(), and calculates the HMAC on
> it and other inode metadata.
> 
> As the LSM infrastructure now can pass to EVM an array with multiple
> xattrs, scan them until the terminator (xattr name NULL), and calculate the
> HMAC on all of them.
> 
> Also, double check that the xattrs array terminator is the first non-filled
> slot (obtained with lsm_get_xattr_slot()). Consumers of the xattrs array,
> such as the initxattrs() callbacks, rely on the terminator.
> 
> Finally, change the name of the lsm_xattr parameter of evm_init_hmac() to
> xattrs, to reflect the new type of information passed.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>

Thanks, Roberto!

Acked-by: Mimi Zohar <zohar@linux.ibm.com>