@@ -72,28 +72,21 @@ static struct ctl_table loadpin_sysctl_table[] = {
{ }
};
-/*
- * This must be called after early kernel init, since then the rootdev
- * is available.
- */
-static void check_pinning_enforcement(struct super_block *mnt_sb)
+static void report_writable(struct super_block *mnt_sb, bool writable)
{
- bool ro = false;
-
/*
* If load pinning is not enforced via a read-only block
* device, allow sysctl to change modes for testing.
*/
if (mnt_sb->s_bdev) {
- ro = bdev_read_only(mnt_sb->s_bdev);
pr_info("%pg (%u:%u): %s\n", mnt_sb->s_bdev,
MAJOR(mnt_sb->s_bdev->bd_dev),
MINOR(mnt_sb->s_bdev->bd_dev),
- ro ? "read-only" : "writable");
+ writable ? "writable" : "read-only");
} else
pr_info("mnt_sb lacks block device, treating as: writable\n");
- if (!ro) {
+ if (writable) {
if (!register_sysctl_paths(loadpin_sysctl_path,
loadpin_sysctl_table))
pr_notice("sysctl registration failed!\n");
@@ -103,12 +96,26 @@ static void check_pinning_enforcement(struct super_block *mnt_sb)
pr_info("load pinning engaged.\n");
}
#else
-static void check_pinning_enforcement(struct super_block *mnt_sb)
+static void report_writable(struct super_block *mnt_sb, bool writable)
{
pr_info("load pinning engaged.\n");
}
#endif
+/*
+ * This must be called after early kernel init, since then the rootdev
+ * is available.
+ */
+static bool sb_is_writable(struct super_block *mnt_sb)
+{
+ bool writable = true;
+
+ if (mnt_sb->s_bdev)
+ writable = !bdev_read_only(mnt_sb->s_bdev);
+
+ return writable;
+}
+
static void loadpin_sb_free_security(struct super_block *mnt_sb)
{
/*
@@ -126,6 +133,7 @@ static int loadpin_check(struct file *file, enum kernel_read_file_id id)
{
struct super_block *load_root;
const char *origin = kernel_read_file_id_str(id);
+ bool load_root_writable;
/* If the file id is excluded, ignore the pinning. */
if ((unsigned int)id < ARRAY_SIZE(ignore_read_file_id) &&
@@ -146,6 +154,7 @@ static int loadpin_check(struct file *file, enum kernel_read_file_id id)
}
load_root = file->f_path.mnt->mnt_sb;
+ load_root_writable = sb_is_writable(load_root);
/* First loaded module/firmware defines the root for all others. */
spin_lock(&pinned_root_spinlock);
@@ -162,7 +171,7 @@ static int loadpin_check(struct file *file, enum kernel_read_file_id id)
* enforcing. This would be purely cosmetic.
*/
spin_unlock(&pinned_root_spinlock);
- check_pinning_enforcement(pinned_root);
+ report_writable(pinned_root, load_root_writable);
report_load(origin, file, "pinned");
} else {
spin_unlock(&pinned_root_spinlock);
In preparation for allowing mounts to shift when not enforced, move read-only checking into a separate helper. Cc: Paul Moore <paul@paul-moore.com> Cc: James Morris <jmorris@namei.org> Cc: "Serge E. Hallyn" <serge@hallyn.com> Cc: linux-security-module@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> --- security/loadpin/loadpin.c | 33 +++++++++++++++++++++------------ 1 file changed, 21 insertions(+), 12 deletions(-)