[PATCH v5.4 v2 0/4] Update SELinuxfs out of tree and then swapover

[PATCH v5.4 v2 0/4] Update SELinuxfs out of tree and then swapover

[Daniel Burgener]

v2: Include all commits from original series, and include commit ids

This is a backport for stable of my series to fix a race condition in
selinuxfs during policy load:

selinux: Create function for selinuxfs directory cleanup
https://lore.kernel.org/selinux/20200819195935.1720168-2-dburgener@linux.microsoft.com/

selinux: Refactor selinuxfs directory populating functions
https://lore.kernel.org/selinux/20200819195935.1720168-3-dburgener@linux.microsoft.com/

selinux: Standardize string literal usage for selinuxfs directory names
https://lore.kernel.org/selinux/20200819195935.1720168-4-dburgener@linux.microsoft.com/

selinux: Create new booleans and class dirs out of tree
https://lore.kernel.org/selinux/20200819195935.1720168-5-dburgener@linux.microsoft.com/

Several changes were necessary to backport.  They are detailed in the
commit message for the third commit in the series.

The bulk of the original cover letter is reproduced below.

In the current implementation, on policy load /sys/fs/selinux is updated
by deleting the previous contents of
/sys/fs/selinux/{class,booleans} and then recreating them.  This means
that there is a period of time when the contents of these directories do
not exist which can cause race conditions as userspace relies on them for
information about the policy.  In addition, it means that error recovery
in the event of failure is challenging.

This patch series follows the design outlined by Al Viro in a previous
e-mail to the list[1].  This approach is to first create the new
directory structures out of tree, then to perform the swapover, and
finally to delete the old directories.  Not handled in this series is
error recovery in the event of failure.

Error recovery in the selinuxfs recreation is unhandled in the current
code, so this series will not cause any regression in this regard.
Handling directory recreation in this manner is a prerequisite to make
proper error handling possible.

In order to demonstrate the race condition that this series fixes, you
can use the following commands:

while true; do cat /sys/fs/selinux/class/service/perms/status
>/dev/null; done &
while true; do load_policy; done;

In the existing code, this will display errors fairly often as the class
lookup fails.  (In normal operation from systemd, this would result in a
permission check which would be allowed or denied based on policy settings
around unknown object classes.) After applying this patch series you
should expect to no longer see such error messages.

Daniel Burgener (4):
  selinux: Create function for selinuxfs directory cleanup
  selinux: Refactor selinuxfs directory populating functions
  selinux: Standardize string literal usage for selinuxfs directory
    names
  selinux: Create new booleans and class dirs out of tree

 security/selinux/selinuxfs.c | 168 +++++++++++++++++++++++++++--------
 1 file changed, 129 insertions(+), 39 deletions(-)

-- 
2.25.4

[PATCH v5.4 v2 1/4] selinux: Create function for selinuxfs directory cleanup

[Daniel Burgener]

upstream commit aeecf4a3fb11954cb10b8bc57e1661a6e4e9f3a9

Separating the cleanup from the creation will simplify two things in
future patches in this series.  First, the creation can be made generic,
to create directories not tied to the selinux_fs_info structure.  Second,
we will ultimately want to reorder creation and deletion so that the
deletions aren't performed until the new directory structures have already
been moved into place.

Signed-off-by: Daniel Burgener <dburgener@linux.microsoft.com>
---
 security/selinux/selinuxfs.c | 39 +++++++++++++++++++++++-------------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index e9eaff90cbcc..092c7295f78d 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -348,6 +348,9 @@ static int sel_make_policycap(struct selinux_fs_info *fsi);
 static struct dentry *sel_make_dir(struct dentry *dir, const char *name,
 			unsigned long *ino);
 
+/* declaration for sel_remove_old_policy_nodes */
+static void sel_remove_entries(struct dentry *de);
+
 static ssize_t sel_read_mls(struct file *filp, char __user *buf,
 				size_t count, loff_t *ppos)
 {
@@ -502,10 +505,32 @@ static const struct file_operations sel_policy_ops = {
 	.llseek		= generic_file_llseek,
 };
 
+static void sel_remove_old_policy_nodes(struct selinux_fs_info *fsi)
+{
+	u32 i;
+
+	/* bool_dir cleanup */
+	for (i = 0; i < fsi->bool_num; i++)
+		kfree(fsi->bool_pending_names[i]);
+	kfree(fsi->bool_pending_names);
+	kfree(fsi->bool_pending_values);
+	fsi->bool_num = 0;
+	fsi->bool_pending_names = NULL;
+	fsi->bool_pending_values = NULL;
+
+	sel_remove_entries(fsi->bool_dir);
+
+	/* class_dir cleanup */
+	sel_remove_entries(fsi->class_dir);
+
+}
+
 static int sel_make_policy_nodes(struct selinux_fs_info *fsi)
 {
 	int ret;
 
+	sel_remove_old_policy_nodes(fsi);
+
 	ret = sel_make_bools(fsi);
 	if (ret) {
 		pr_err("SELinux: failed to load policy booleans\n");
@@ -1336,17 +1361,6 @@ static int sel_make_bools(struct selinux_fs_info *fsi)
 	int *values = NULL;
 	u32 sid;
 
-	/* remove any existing files */
-	for (i = 0; i < fsi->bool_num; i++)
-		kfree(fsi->bool_pending_names[i]);
-	kfree(fsi->bool_pending_names);
-	kfree(fsi->bool_pending_values);
-	fsi->bool_num = 0;
-	fsi->bool_pending_names = NULL;
-	fsi->bool_pending_values = NULL;
-
-	sel_remove_entries(dir);
-
 	ret = -ENOMEM;
 	page = (char *)get_zeroed_page(GFP_KERNEL);
 	if (!page)
@@ -1798,9 +1812,6 @@ static int sel_make_classes(struct selinux_fs_info *fsi)
 	int rc, nclasses, i;
 	char **classes;
 
-	/* delete any existing entries */
-	sel_remove_entries(fsi->class_dir);
-
 	rc = security_get_classes(fsi->state, &classes, &nclasses);
 	if (rc)
 		return rc;
-- 
2.25.4

[PATCH v5.4 v2 2/4] selinux: Refactor selinuxfs directory populating functions

[Daniel Burgener]

upstream commit 66ec384ad3044d63c9726493a412a2ad5317eae5

Make sel_make_bools and sel_make_classes take the specific elements of
selinux_fs_info that they need rather than the entire struct.

This will allow a future patch to pass temporary elements that are not in
the selinux_fs_info struct to these functions so that the original elements
can be preserved until we are ready to perform the switch over.

Signed-off-by: Daniel Burgener <dburgener@linux.microsoft.com>
---
 security/selinux/selinuxfs.c | 40 +++++++++++++++++++++---------------
 1 file changed, 24 insertions(+), 16 deletions(-)

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 092c7295f78d..ea21f3ef4a6f 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -340,8 +340,11 @@ static const struct file_operations sel_policyvers_ops = {
 };
 
 /* declaration for sel_write_load */
-static int sel_make_bools(struct selinux_fs_info *fsi);
-static int sel_make_classes(struct selinux_fs_info *fsi);
+static int sel_make_bools(struct selinux_fs_info *fsi, struct dentry *bool_dir,
+			  unsigned int *bool_num, char ***bool_pending_names,
+			  unsigned int **bool_pending_values);
+static int sel_make_classes(struct selinux_fs_info *fsi, struct dentry *class_dir,
+			    unsigned long *last_class_ino);
 static int sel_make_policycap(struct selinux_fs_info *fsi);
 
 /* declaration for sel_make_class_dirs */
@@ -531,13 +534,15 @@ static int sel_make_policy_nodes(struct selinux_fs_info *fsi)
 
 	sel_remove_old_policy_nodes(fsi);
 
-	ret = sel_make_bools(fsi);
+	ret = sel_make_bools(fsi, fsi->bool_dir, &fsi->bool_num,
+			     &fsi->bool_pending_names, &fsi->bool_pending_values);
 	if (ret) {
 		pr_err("SELinux: failed to load policy booleans\n");
 		return ret;
 	}
 
-	ret = sel_make_classes(fsi);
+	ret = sel_make_classes(fsi, fsi->class_dir,
+			       &fsi->last_class_ino);
 	if (ret) {
 		pr_err("SELinux: failed to load policy classes\n");
 		return ret;
@@ -1348,12 +1353,13 @@ static void sel_remove_entries(struct dentry *de)
 
 #define BOOL_DIR_NAME "booleans"
 
-static int sel_make_bools(struct selinux_fs_info *fsi)
+static int sel_make_bools(struct selinux_fs_info *fsi, struct dentry *bool_dir,
+			  unsigned int *bool_num, char ***bool_pending_names,
+			  unsigned int **bool_pending_values)
 {
 	int i, ret;
 	ssize_t len;
 	struct dentry *dentry = NULL;
-	struct dentry *dir = fsi->bool_dir;
 	struct inode *inode = NULL;
 	struct inode_security_struct *isec;
 	char **names = NULL, *page;
@@ -1372,12 +1378,12 @@ static int sel_make_bools(struct selinux_fs_info *fsi)
 
 	for (i = 0; i < num; i++) {
 		ret = -ENOMEM;
-		dentry = d_alloc_name(dir, names[i]);
+		dentry = d_alloc_name(bool_dir, names[i]);
 		if (!dentry)
 			goto out;
 
 		ret = -ENOMEM;
-		inode = sel_make_inode(dir->d_sb, S_IFREG | S_IRUGO | S_IWUSR);
+		inode = sel_make_inode(bool_dir->d_sb, S_IFREG | S_IRUGO | S_IWUSR);
 		if (!inode) {
 			dput(dentry);
 			goto out;
@@ -1406,9 +1412,9 @@ static int sel_make_bools(struct selinux_fs_info *fsi)
 		inode->i_ino = i|SEL_BOOL_INO_OFFSET;
 		d_add(dentry, inode);
 	}
-	fsi->bool_num = num;
-	fsi->bool_pending_names = names;
-	fsi->bool_pending_values = values;
+	*bool_num = num;
+	*bool_pending_names = names;
+	*bool_pending_values = values;
 
 	free_page((unsigned long)page);
 	return 0;
@@ -1421,7 +1427,7 @@ static int sel_make_bools(struct selinux_fs_info *fsi)
 		kfree(names);
 	}
 	kfree(values);
-	sel_remove_entries(dir);
+	sel_remove_entries(bool_dir);
 
 	return ret;
 }
@@ -1806,7 +1812,9 @@ static int sel_make_class_dir_entries(char *classname, int index,
 	return rc;
 }
 
-static int sel_make_classes(struct selinux_fs_info *fsi)
+static int sel_make_classes(struct selinux_fs_info *fsi,
+			    struct dentry *class_dir,
+			    unsigned long *last_class_ino)
 {
 
 	int rc, nclasses, i;
@@ -1817,13 +1825,13 @@ static int sel_make_classes(struct selinux_fs_info *fsi)
 		return rc;
 
 	/* +2 since classes are 1-indexed */
-	fsi->last_class_ino = sel_class_to_ino(nclasses + 2);
+	*last_class_ino = sel_class_to_ino(nclasses + 2);
 
 	for (i = 0; i < nclasses; i++) {
 		struct dentry *class_name_dir;
 
-		class_name_dir = sel_make_dir(fsi->class_dir, classes[i],
-					      &fsi->last_class_ino);
+		class_name_dir = sel_make_dir(class_dir, classes[i],
+					      last_class_ino);
 		if (IS_ERR(class_name_dir)) {
 			rc = PTR_ERR(class_name_dir);
 			goto out;
-- 
2.25.4

[PATCH v5.4 v2 3/4] selinux: Standardize string literal usage for selinuxfs directory names

[Daniel Burgener]

upstream commit 613ba18798ac3cf257ecff65d490e8f1aa323588

Switch class and policy_capabilities directory names to be referred to with
global constants, consistent with booleans directory name.  This will allow
for easy consistency of naming in future development.

Signed-off-by: Daniel Burgener <dburgener@linux.microsoft.com>
---
 security/selinux/selinuxfs.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index ea21f3ef4a6f..ae018aaa4391 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -117,6 +117,10 @@ static void selinux_fs_info_free(struct super_block *sb)
 #define SEL_POLICYCAP_INO_OFFSET	0x08000000
 #define SEL_INO_MASK			0x00ffffff
 
+#define BOOL_DIR_NAME "booleans"
+#define CLASS_DIR_NAME "class"
+#define POLICYCAP_DIR_NAME "policy_capabilities"
+
 #define TMPBUFLEN	12
 static ssize_t sel_read_enforce(struct file *filp, char __user *buf,
 				size_t count, loff_t *ppos)
@@ -2000,14 +2004,14 @@ static int sel_fill_super(struct super_block *sb, struct fs_context *fc)
 	if (ret)
 		goto err;
 
-	fsi->class_dir = sel_make_dir(sb->s_root, "class", &fsi->last_ino);
+	fsi->class_dir = sel_make_dir(sb->s_root, CLASS_DIR_NAME, &fsi->last_ino);
 	if (IS_ERR(fsi->class_dir)) {
 		ret = PTR_ERR(fsi->class_dir);
 		fsi->class_dir = NULL;
 		goto err;
 	}
 
-	fsi->policycap_dir = sel_make_dir(sb->s_root, "policy_capabilities",
+	fsi->policycap_dir = sel_make_dir(sb->s_root, POLICYCAP_DIR_NAME,
 					  &fsi->last_ino);
 	if (IS_ERR(fsi->policycap_dir)) {
 		ret = PTR_ERR(fsi->policycap_dir);
-- 
2.25.4

[PATCH v5.4 v2 4/4] selinux: Create new booleans and class dirs out of tree

[Daniel Burgener]

upstream commit 0eea6091539b15572cd278b8d62893c058bdb292

In order to avoid concurrency issues around selinuxfs resource availability
during policy load, we first create new directories out of tree for
reloaded resources, then swap them in, and finally delete the old versions.

This fix focuses on concurrency in each of the two subtrees swapped, and
not concurrency between the trees.  This means that it is still possible
that subsequent reads to eg the booleans directory and the class directory
during a policy load could see the old state for one and the new for the other.
The problem of ensuring that policy loads are fully atomic from the perspective
of userspace is larger than what is dealt with here.  This commit focuses on
ensuring that the directories contents always match either the new or the old
policy state from the perspective of userspace.

In the previous implementation, on policy load /sys/fs/selinux is updated
by deleting the previous contents of
/sys/fs/selinux/{class,booleans} and then recreating them.  This means
that there is a period of time when the contents of these directories do not
exist which can cause race conditions as userspace relies on them for
information about the policy.  In addition, it means that error recovery in
the event of failure is challenging.

In order to demonstrate the race condition that this series fixes, you
can use the following commands:

while true; do cat /sys/fs/selinux/class/service/perms/status
>/dev/null; done &
while true; do load_policy; done;

In the existing code, this will display errors fairly often as the class
lookup fails.  (In normal operation from systemd, this would result in a
permission check which would be allowed or denied based on policy settings
around unknown object classes.) After applying this patch series you
should expect to no longer see such error messages.

This has been backported to 5.4 for inclusion in stable.  Because prior to this
series in the main kernel some refactoring of SELinux policy loading had been
done, the backport required changing some function call arguments.

The most significant change of note in the backport is as follows:

In previous versions of the kernel, on a policy load, three directories
in the selinuxfs were recreated: class, booleans and policy_capabilities.
Changes to the selinuxfs code after 5.4 but prior to this series removed
the recreation of the policy_capabilities code, so that was not modified in
this series.  For this backport, I left the existing recreation functionality
of policy_capabilities intact, modifying only the class and booleans
directories, as in the original series.

Signed-off-by: Daniel Burgener <dburgener@linux.microsoft.com>
---
 security/selinux/selinuxfs.c | 119 +++++++++++++++++++++++++++--------
 1 file changed, 93 insertions(+), 26 deletions(-)

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index ae018aaa4391..3716f49b547d 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -20,6 +20,7 @@
 #include <linux/fs_context.h>
 #include <linux/mount.h>
 #include <linux/mutex.h>
+#include <linux/namei.h>
 #include <linux/init.h>
 #include <linux/string.h>
 #include <linux/security.h>
@@ -355,7 +356,11 @@ static int sel_make_policycap(struct selinux_fs_info *fsi);
 static struct dentry *sel_make_dir(struct dentry *dir, const char *name,
 			unsigned long *ino);
 
-/* declaration for sel_remove_old_policy_nodes */
+/* declaration for sel_make_policy_nodes */
+static struct dentry *sel_make_disconnected_dir(struct super_block *sb,
+						unsigned long *ino);
+
+/* declaration for sel_make_policy_nodes */
 static void sel_remove_entries(struct dentry *de);
 
 static ssize_t sel_read_mls(struct file *filp, char __user *buf,
@@ -512,53 +517,101 @@ static const struct file_operations sel_policy_ops = {
 	.llseek		= generic_file_llseek,
 };
 
-static void sel_remove_old_policy_nodes(struct selinux_fs_info *fsi)
+static void sel_remove_old_bool_data(unsigned int bool_num, char **bool_names,
+				unsigned int *bool_values)
 {
 	u32 i;
 
 	/* bool_dir cleanup */
-	for (i = 0; i < fsi->bool_num; i++)
-		kfree(fsi->bool_pending_names[i]);
-	kfree(fsi->bool_pending_names);
-	kfree(fsi->bool_pending_values);
-	fsi->bool_num = 0;
-	fsi->bool_pending_names = NULL;
-	fsi->bool_pending_values = NULL;
-
-	sel_remove_entries(fsi->bool_dir);
-
-	/* class_dir cleanup */
-	sel_remove_entries(fsi->class_dir);
-
+	for (i = 0; i < bool_num; i++)
+		kfree(bool_names[i]);
+	kfree(bool_names);
+	kfree(bool_values);
 }
 
+#define BOOL_DIR_NAME "booleans"
+
 static int sel_make_policy_nodes(struct selinux_fs_info *fsi)
 {
-	int ret;
+	int ret = 0;
+	struct dentry *tmp_parent, *tmp_bool_dir, *tmp_class_dir, *old_dentry;
+	unsigned int tmp_bool_num, old_bool_num;
+	char **tmp_bool_names, **old_bool_names;
+	unsigned int *tmp_bool_values, *old_bool_values;
+	unsigned long tmp_ino = fsi->last_ino; /* Don't increment last_ino in this function */
 
-	sel_remove_old_policy_nodes(fsi);
+	tmp_parent = sel_make_disconnected_dir(fsi->sb, &tmp_ino);
+	if (IS_ERR(tmp_parent))
+		return PTR_ERR(tmp_parent);
 
-	ret = sel_make_bools(fsi, fsi->bool_dir, &fsi->bool_num,
-			     &fsi->bool_pending_names, &fsi->bool_pending_values);
+	tmp_ino = fsi->bool_dir->d_inode->i_ino - 1; /* sel_make_dir will increment and set */
+	tmp_bool_dir = sel_make_dir(tmp_parent, BOOL_DIR_NAME, &tmp_ino);
+	if (IS_ERR(tmp_bool_dir)) {
+		ret = PTR_ERR(tmp_bool_dir);
+		goto out;
+	}
+
+	tmp_ino = fsi->class_dir->d_inode->i_ino - 1; /* sel_make_dir will increment and set */
+	tmp_class_dir = sel_make_dir(tmp_parent, CLASS_DIR_NAME, &tmp_ino);
+	if (IS_ERR(tmp_class_dir)) {
+		ret = PTR_ERR(tmp_class_dir);
+		goto out;
+	}
+
+	ret = sel_make_bools(fsi, tmp_bool_dir, &tmp_bool_num,
+			     &tmp_bool_names, &tmp_bool_values);
 	if (ret) {
 		pr_err("SELinux: failed to load policy booleans\n");
-		return ret;
+		goto out;
 	}
 
-	ret = sel_make_classes(fsi, fsi->class_dir,
+	ret = sel_make_classes(fsi, tmp_class_dir,
 			       &fsi->last_class_ino);
 	if (ret) {
 		pr_err("SELinux: failed to load policy classes\n");
-		return ret;
+		goto out;
 	}
 
 	ret = sel_make_policycap(fsi);
 	if (ret) {
 		pr_err("SELinux: failed to load policy capabilities\n");
-		return ret;
+		goto out;
 	}
 
-	return 0;
+	/* booleans */
+	old_dentry = fsi->bool_dir;
+	lock_rename(tmp_bool_dir, old_dentry);
+	d_exchange(tmp_bool_dir, fsi->bool_dir);
+
+	old_bool_num = fsi->bool_num;
+	old_bool_names = fsi->bool_pending_names;
+	old_bool_values = fsi->bool_pending_values;
+
+	fsi->bool_num = tmp_bool_num;
+	fsi->bool_pending_names = tmp_bool_names;
+	fsi->bool_pending_values = tmp_bool_values;
+
+	sel_remove_old_bool_data(old_bool_num, old_bool_names, old_bool_values);
+
+	fsi->bool_dir = tmp_bool_dir;
+	unlock_rename(tmp_bool_dir, old_dentry);
+
+	/* classes */
+	old_dentry = fsi->class_dir;
+	lock_rename(tmp_class_dir, old_dentry);
+	d_exchange(tmp_class_dir, fsi->class_dir);
+	fsi->class_dir = tmp_class_dir;
+	unlock_rename(tmp_class_dir, old_dentry);
+
+out:
+	/* Since the other temporary dirs are children of tmp_parent
+	 * this will handle all the cleanup in the case of a failure before
+	 * the swapover
+	 */
+	sel_remove_entries(tmp_parent);
+	dput(tmp_parent); /* d_genocide() only handles the children */
+
+	return ret;
 }
 
 static ssize_t sel_write_load(struct file *file, const char __user *buf,
@@ -1355,8 +1408,6 @@ static void sel_remove_entries(struct dentry *de)
 	shrink_dcache_parent(de);
 }
 
-#define BOOL_DIR_NAME "booleans"
-
 static int sel_make_bools(struct selinux_fs_info *fsi, struct dentry *bool_dir,
 			  unsigned int *bool_num, char ***bool_pending_names,
 			  unsigned int **bool_pending_values)
@@ -1914,6 +1965,22 @@ static struct dentry *sel_make_dir(struct dentry *dir, const char *name,
 	return dentry;
 }
 
+static struct dentry *sel_make_disconnected_dir(struct super_block *sb,
+						unsigned long *ino)
+{
+	struct inode *inode = sel_make_inode(sb, S_IFDIR | S_IRUGO | S_IXUGO);
+
+	if (!inode)
+		return ERR_PTR(-ENOMEM);
+
+	inode->i_op = &simple_dir_inode_operations;
+	inode->i_fop = &simple_dir_operations;
+	inode->i_ino = ++(*ino);
+	/* directory inodes start off with i_nlink == 2 (for "." entry) */
+	inc_nlink(inode);
+	return d_obtain_alias(inode);
+}
+
 #define NULL_FILE_NAME "null"
 
 static int sel_fill_super(struct super_block *sb, struct fs_context *fc)
-- 
2.25.4

Re: [PATCH v5.4 v2 0/4] Update SELinuxfs out of tree and then swapover

[Greg KH]

On Fri, Oct 16, 2020 at 09:48:31AM -0400, Daniel Burgener wrote:
> v2: Include all commits from original series, and include commit ids
> 
> This is a backport for stable of my series to fix a race condition in
> selinuxfs during policy load:

Has this race condition always been present, or is this a regression
that is being fixed from previously working kernels?

If it's always been present, why not just use 5.9 to solve it?

thanks,

greg k-h

Re: [PATCH v5.4 v2 0/4] Update SELinuxfs out of tree and then swapover

[Sasha Levin]

On Fri, Oct 16, 2020 at 05:01:20PM +0200, Greg KH wrote:
>On Fri, Oct 16, 2020 at 09:48:31AM -0400, Daniel Burgener wrote:
>> v2: Include all commits from original series, and include commit ids
>>
>> This is a backport for stable of my series to fix a race condition in
>> selinuxfs during policy load:
>
>Has this race condition always been present, or is this a regression
>that is being fixed from previously working kernels?

So this issue has always been there, but:

>If it's always been present, why not just use 5.9 to solve it?

Because it was merged for 5.10 rather than 5.9, which is a few months
out, so Daniel is looking to see if we can have it in 5.8/5.4 to close
the gap.

-- 
Thanks,
Sasha

Re: [PATCH v5.4 v2 0/4] Update SELinuxfs out of tree and then swapover

[Greg KH]

On Fri, Oct 16, 2020 at 11:38:23AM -0400, Sasha Levin wrote:
> On Fri, Oct 16, 2020 at 05:01:20PM +0200, Greg KH wrote:
> > On Fri, Oct 16, 2020 at 09:48:31AM -0400, Daniel Burgener wrote:
> > > v2: Include all commits from original series, and include commit ids
> > > 
> > > This is a backport for stable of my series to fix a race condition in
> > > selinuxfs during policy load:
> > 
> > Has this race condition always been present, or is this a regression
> > that is being fixed from previously working kernels?
> 
> So this issue has always been there, but:
> 
> > If it's always been present, why not just use 5.9 to solve it?
> 
> Because it was merged for 5.10 rather than 5.9, which is a few months
> out, so Daniel is looking to see if we can have it in 5.8/5.4 to close
> the gap.

I would have to wait for 5.10-rc1 at the earliest, and get the selinux
maintainers ack for this :)

thanks,

greg k-h

Re: [PATCH v5.4 v2 0/4] Update SELinuxfs out of tree and then swapover

[Sasha Levin]

On Fri, Oct 16, 2020 at 05:44:43PM +0200, Greg KH wrote:
>On Fri, Oct 16, 2020 at 11:38:23AM -0400, Sasha Levin wrote:
>> On Fri, Oct 16, 2020 at 05:01:20PM +0200, Greg KH wrote:
>> > On Fri, Oct 16, 2020 at 09:48:31AM -0400, Daniel Burgener wrote:
>> > > v2: Include all commits from original series, and include commit ids
>> > >
>> > > This is a backport for stable of my series to fix a race condition in
>> > > selinuxfs during policy load:
>> >
>> > Has this race condition always been present, or is this a regression
>> > that is being fixed from previously working kernels?
>>
>> So this issue has always been there, but:
>>
>> > If it's always been present, why not just use 5.9 to solve it?
>>
>> Because it was merged for 5.10 rather than 5.9, which is a few months
>> out, so Daniel is looking to see if we can have it in 5.8/5.4 to close
>> the gap.
>
>I would have to wait for 5.10-rc1 at the earliest, and get the selinux
>maintainers ack for this :)

No objections; if the selinux folks feel unhappy with this it'll just
wait for 5.10.

-- 
Thanks,
Sasha

Re: [PATCH v5.4 v2 0/4] Update SELinuxfs out of tree and then swapover

[Daniel Burgener]

On 10/16/20 11:49 AM, Sasha Levin wrote:
> On Fri, Oct 16, 2020 at 05:44:43PM +0200, Greg KH wrote:
>> On Fri, Oct 16, 2020 at 11:38:23AM -0400, Sasha Levin wrote:
>>> On Fri, Oct 16, 2020 at 05:01:20PM +0200, Greg KH wrote:
>>> > On Fri, Oct 16, 2020 at 09:48:31AM -0400, Daniel Burgener wrote:
>>> > > v2: Include all commits from original series, and include commit 
>>> ids
>>> > >
>>> > > This is a backport for stable of my series to fix a race 
>>> condition in
>>> > > selinuxfs during policy load:
>>> >
>>> > Has this race condition always been present, or is this a regression
>>> > that is being fixed from previously working kernels?
>>>
>>> So this issue has always been there, but:
>>>
>>> > If it's always been present, why not just use 5.9 to solve it?
>>>
>>> Because it was merged for 5.10 rather than 5.9, which is a few months
>>> out, so Daniel is looking to see if we can have it in 5.8/5.4 to close
>>> the gap.
>>
>> I would have to wait for 5.10-rc1 at the earliest, and get the selinux
>> maintainers ack for this :)
>
> No objections; if the selinux folks feel unhappy with this it'll just
> wait for 5.10.
>
Yes, that's fine from my end as well.  We can carry this series out of 
tree in the interim.  Thanks!

-Daniel

Re: [PATCH v5.4 v2 0/4] Update SELinuxfs out of tree and then swapover

[Paul Moore]

On Fri, Oct 16, 2020 at 12:01 PM Daniel Burgener
<dburgener@linux.microsoft.com> wrote:
> On 10/16/20 11:49 AM, Sasha Levin wrote:
> > On Fri, Oct 16, 2020 at 05:44:43PM +0200, Greg KH wrote:
> >> On Fri, Oct 16, 2020 at 11:38:23AM -0400, Sasha Levin wrote:
> >>> On Fri, Oct 16, 2020 at 05:01:20PM +0200, Greg KH wrote:
> >>> > On Fri, Oct 16, 2020 at 09:48:31AM -0400, Daniel Burgener wrote:
> >>> > > v2: Include all commits from original series, and include commit
> >>> ids
> >>> > >
> >>> > > This is a backport for stable of my series to fix a race
> >>> condition in
> >>> > > selinuxfs during policy load:
> >>> >
> >>> > Has this race condition always been present, or is this a regression
> >>> > that is being fixed from previously working kernels?
> >>>
> >>> So this issue has always been there, but:
> >>>
> >>> > If it's always been present, why not just use 5.9 to solve it?
> >>>
> >>> Because it was merged for 5.10 rather than 5.9, which is a few months
> >>> out, so Daniel is looking to see if we can have it in 5.8/5.4 to close
> >>> the gap.
> >>
> >> I would have to wait for 5.10-rc1 at the earliest, and get the selinux
> >> maintainers ack for this :)
> >
> > No objections; if the selinux folks feel unhappy with this it'll just
> > wait for 5.10.
> >
> Yes, that's fine from my end as well.  We can carry this series out of
> tree in the interim.  Thanks!

I tend to be pretty conservative when it comes to backporting patches
to -stable, and since this is both a) big and b) fixes a problem that
has existed since the dawn of selinuxfs (and possibly longer <g>) I
think the smart thing to do is to wait for v5.10.

-- 
paul moore
www.paul-moore.com