linux-kernel - [PATCH 2/3] LSM: allocate mnt_opts blobs instead of module specific data

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Message-ID: <20250617210105.17479-3-casey@schaufler-ca.com>
Date: Tue, 17 Jun 2025 14:01:04 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: casey@...aufler-ca.com,
	paul@...l-moore.com,
	eparis@...hat.com,
	linux-security-module@...r.kernel.org
Cc: jmorris@...ei.org,
	serge@...lyn.com,
	keescook@...omium.org,
	john.johansen@...onical.com,
	penguin-kernel@...ove.sakura.ne.jp,
	stephen.smalley.work@...il.com,
	linux-kernel@...r.kernel.org,
	selinux@...r.kernel.org
Subject: [PATCH 2/3] LSM: allocate mnt_opts blobs instead of module specific data

Replace allocations of LSM specific mount data with the
shared mnt_opts blob.

Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
---
 include/linux/lsm_hooks.h  |  1 +
 security/security.c        | 12 ++++++++++++
 security/selinux/hooks.c   | 10 +++++++---
 security/smack/smack_lsm.c |  4 ++--
 4 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 9741c76e4654..1871ebc5833b 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -219,4 +219,5 @@ static inline struct xattr *lsm_get_xattr_slot(struct xattr *xattrs,
 	return &xattrs[(*xattr_count)++];
 }
 
+extern void *lsm_mnt_opts_alloc(gfp_t priority);
 #endif /* ! __LINUX_LSM_HOOKS_H */
diff --git a/security/security.c b/security/security.c
index 8a4e0f70e49d..ec61fb7e6492 100644
--- a/security/security.c
+++ b/security/security.c
@@ -904,6 +904,18 @@ void security_sb_free(struct super_block *sb)
 	sb->s_security = NULL;
 }
 
+/**
+ * lsm_mnt_opts_alloc - allocate a mnt_opts blob
+ * @priority: memory allocation priority
+ *
+ * Returns a newly allocated mnt_opts blob or NULL if
+ * memory isn't available.
+ */
+void *lsm_mnt_opts_alloc(gfp_t priority)
+{
+	return kzalloc(blob_sizes.lbs_mnt_opts, priority);
+}
+
 /**
  * security_free_mnt_opts() - Free memory associated with mount options
  * @mnt_opts: LSM processed mount options
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 88cd1d56081a..f7eda0cce68f 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2808,7 +2808,7 @@ static int selinux_fs_context_submount(struct fs_context *fc,
 	if (!(sbsec->flags & (FSCONTEXT_MNT|CONTEXT_MNT|DEFCONTEXT_MNT)))
 		return 0;
 
-	opts = kzalloc(sizeof(*opts), GFP_KERNEL);
+	opts = lsm_mnt_opts_alloc(GFP_KERNEL);
 	if (!opts)
 		return -ENOMEM;
 
@@ -2830,8 +2830,12 @@ static int selinux_fs_context_dup(struct fs_context *fc,
 	if (!src)
 		return 0;
 
-	fc->security = kmemdup(src, sizeof(*src), GFP_KERNEL);
-	return fc->security ? 0 : -ENOMEM;
+	fc->security = lsm_mnt_opts_alloc(GFP_KERNEL);
+	if (!fc->security)
+		return -ENOMEM;
+
+	memcpy(fc->security, src, sizeof(*src));
+	return 0;
 }
 
 static const struct fs_parameter_spec selinux_fs_parameters[] = {
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 44bd92410425..1d456df40096 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -622,7 +622,7 @@ static int smack_fs_context_submount(struct fs_context *fc,
 	struct smack_mnt_opts *ctx;
 	struct inode_smack *isp;
 
-	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+	ctx = lsm_mnt_opts_alloc(GFP_KERNEL);
 	if (!ctx)
 		return -ENOMEM;
 	fc->security = ctx;
@@ -673,7 +673,7 @@ static int smack_fs_context_dup(struct fs_context *fc,
 	if (!src)
 		return 0;
 
-	fc->security = kzalloc(sizeof(struct smack_mnt_opts), GFP_KERNEL);
+	fc->security = lsm_mnt_opts_alloc(GFP_KERNEL);
 	if (!fc->security)
 		return -ENOMEM;
 
-- 
2.47.0