Merge tag 'lsm-pr-20240911' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm

Pull lsm updates from Paul Moore:

 - Move the LSM framework to static calls

   This transitions the vast majority of the LSM callbacks into static
   calls. Those callbacks which haven't been converted were left as-is
   due to the general ugliness of the changes required to support the
   static call conversion; we can revisit those callbacks at a future
   date.

 - Add the Integrity Policy Enforcement (IPE) LSM

   This adds a new LSM, Integrity Policy Enforcement (IPE). There is
   plenty of documentation about IPE in this patches, so I'll refrain
   from going into too much detail here, but the basic motivation behind
   IPE is to provide a mechanism such that administrators can restrict
   execution to only those binaries which come from integrity protected
   storage, e.g. a dm-verity protected filesystem. You will notice that
   IPE requires additional LSM hooks in the initramfs, dm-verity, and
   fs-verity code, with the associated patches carrying ACK/review tags
   from the associated maintainers. We couldn't find an obvious
   maintainer for the initramfs code, but the IPE patchset has been
   widely posted over several years.

   Both Deven Bowers and Fan Wu have contributed to IPE's development
   over the past several years, with Fan Wu agreeing to serve as the IPE
   maintainer moving forward. Once IPE is accepted into your tree, I'll
   start working with Fan to ensure he has the necessary accounts, keys,
   etc. so that he can start submitting IPE pull requests to you
   directly during the next merge window.

 - Move the lifecycle management of the LSM blobs to the LSM framework

   Management of the LSM blobs (the LSM state buffers attached to
   various kernel structs, typically via a void pointer named "security"
   or similar) has been mixed, some blobs were allocated/managed by
   individual LSMs, others were managed by the LSM framework itself.

   Starting with this pull we move management of all the LSM blobs,
   minus the XFRM blob, into the framework itself, improving consistency
   across LSMs, and reducing the amount of duplicated code across LSMs.
   Due to some additional work required to migrate the XFRM blob, it has
   been left as a todo item for a later date; from a practical
   standpoint this omission should have little impact as only SELinux
   provides a XFRM LSM implementation.

 - Fix problems with the LSM's handling of F_SETOWN

   The LSM hook for the fcntl(F_SETOWN) operation had a couple of
   problems: it was racy with itself, and it was disconnected from the
   associated DAC related logic in such a way that the LSM state could
   be updated in cases where the DAC state would not. We fix both of
   these problems by moving the security_file_set_fowner() hook into the
   same section of code where the DAC attributes are updated. Not only
   does this resolve the DAC/LSM synchronization issue, but as that code
   block is protected by a lock, it also resolve the race condition.

 - Fix potential problems with the security_inode_free() LSM hook

   Due to use of RCU to protect inodes and the placement of the LSM hook
   associated with freeing the inode, there is a bit of a challenge when
   it comes to managing any LSM state associated with an inode. The VFS
   folks are not open to relocating the LSM hook so we have to get
   creative when it comes to releasing an inode's LSM state.
   Traditionally we have used a single LSM callback within the hook that
   is triggered when the inode is "marked for death", but not actually
   released due to RCU.

   Unfortunately, this causes problems for LSMs which want to take an
   action when the inode's associated LSM state is actually released; so
   we add an additional LSM callback, inode_free_security_rcu(), that is
   called when the inode's LSM state is released in the RCU free
   callback.

 - Refactor two LSM hooks to better fit the LSM return value patterns

   The vast majority of the LSM hooks follow the "return 0 on success,
   negative values on failure" pattern, however, there are a small
   handful that have unique return value behaviors which has caused
   confusion in the past and makes it difficult for the BPF verifier to
   properly vet BPF LSM programs. This includes patches to
   convert two of these"special" LSM hooks to the common 0/-ERRNO pattern.

 - Various cleanups and improvements

   A handful of patches to remove redundant code, better leverage the
   IS_ERR_OR_NULL() helper, add missing "static" markings, and do some
   minor style fixups.

* tag 'lsm-pr-20240911' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm: (40 commits)
  security: Update file_set_fowner documentation
  fs: Fix file_set_fowner LSM hook inconsistencies
  lsm: Use IS_ERR_OR_NULL() helper function
  lsm: remove LSM_COUNT and LSM_CONFIG_COUNT
  ipe: Remove duplicated include in ipe.c
  lsm: replace indirect LSM hook calls with static calls
  lsm: count the LSMs enabled at compile time
  kernel: Add helper macros for loop unrolling
  init/main.c: Initialize early LSMs after arch code, static keys and calls.
  MAINTAINERS: add IPE entry with Fan Wu as maintainer
  documentation: add IPE documentation
  ipe: kunit test for parser
  scripts: add boot policy generation program
  ipe: enable support for fs-verity as a trust provider
  fsverity: expose verified fsverity built-in signatures to LSMs
  lsm: add security_inode_setintegrity() hook
  ipe: add support for dm-verity as a trust provider
  dm-verity: expose root hash digest and signature data to LSMs
  block,lsm: add LSM blob and new LSM hooks for block devices
  ipe: add permissive toggle
  ...

1 files changed, 84 insertions, 45 deletions

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index a2ade0ffe9e7..090d1d3e19fe 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -30,19 +30,47 @@
 #include <linux/init.h>
 #include <linux/rculist.h>
 #include <linux/xattr.h>
+#include <linux/static_call.h>
+#include <linux/unroll.h>
+#include <linux/jump_label.h>
+#include <linux/lsm_count.h>
 
 union security_list_options {
 	#define LSM_HOOK(RET, DEFAULT, NAME, ...) RET (*NAME)(__VA_ARGS__);
 	#include "lsm_hook_defs.h"
 	#undef LSM_HOOK
+	void *lsm_func_addr;
 };
 
-struct security_hook_heads {
-	#define LSM_HOOK(RET, DEFAULT, NAME, ...) struct hlist_head NAME;
-	#include "lsm_hook_defs.h"
-	#undef LSM_HOOK
+/*
+ * @key: static call key as defined by STATIC_CALL_KEY
+ * @trampoline: static call trampoline as defined by STATIC_CALL_TRAMP
+ * @hl: The security_hook_list as initialized by the owning LSM.
+ * @active: Enabled when the static call has an LSM hook associated.
+ */
+struct lsm_static_call {
+	struct static_call_key *key;
+	void *trampoline;
+	struct security_hook_list *hl;
+	/* this needs to be true or false based on what the key defaults to */
+	struct static_key_false *active;
 } __randomize_layout;
 
+/*
+ * Table of the static calls for each LSM hook.
+ * Once the LSMs are initialized, their callbacks will be copied to these
+ * tables such that the calls are filled backwards (from last to first).
+ * This way, we can jump directly to the first used static call, and execute
+ * all of them after. This essentially makes the entry point
+ * dynamic to adapt the number of static calls to the number of callbacks.
+ */
+struct lsm_static_calls_table {
+	#define LSM_HOOK(RET, DEFAULT, NAME, ...) \
+		struct lsm_static_call NAME[MAX_LSM_COUNT];
+	#include <linux/lsm_hook_defs.h>
+	#undef LSM_HOOK
+} __packed __randomize_layout;
+
 /**
  * struct lsm_id - Identify a Linux Security Module.
  * @lsm: name of the LSM, must be approved by the LSM maintainers
@@ -51,53 +79,45 @@ struct security_hook_heads {
  * Contains the information that identifies the LSM.
  */
 struct lsm_id {
-	const char	*name;
-	u64		id;
+	const char *name;
+	u64 id;
 };
 
 /*
  * Security module hook list structure.
  * For use with generic list macros for common operations.
+ *
+ * struct security_hook_list - Contents of a cacheable, mappable object.
+ * @scalls: The beginning of the array of static calls assigned to this hook.
+ * @hook: The callback for the hook.
+ * @lsm: The name of the lsm that owns this hook.
  */
 struct security_hook_list {
-	struct hlist_node		list;
-	struct hlist_head		*head;
-	union security_list_options	hook;
-	const struct lsm_id		*lsmid;
+	struct lsm_static_call *scalls;
+	union security_list_options hook;
+	const struct lsm_id *lsmid;
 } __randomize_layout;
 
 /*
  * Security blob size or offset data.
  */
 struct lsm_blob_sizes {
-	int	lbs_cred;
-	int	lbs_file;
-	int	lbs_inode;
-	int	lbs_superblock;
-	int	lbs_ipc;
-	int	lbs_msg_msg;
-	int	lbs_task;
-	int	lbs_xattr_count; /* number of xattr slots in new_xattrs array */
+	int lbs_cred;
+	int lbs_file;
+	int lbs_ib;
+	int lbs_inode;
+	int lbs_sock;
+	int lbs_superblock;
+	int lbs_ipc;
+	int lbs_key;
+	int lbs_msg_msg;
+	int lbs_perf_event;
+	int lbs_task;
+	int lbs_xattr_count; /* number of xattr slots in new_xattrs array */
+	int lbs_tun_dev;
+	int lbs_bdev;
 };
 
-/**
- * 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).
@@ -110,11 +130,11 @@ static inline struct xattr *lsm_get_xattr_slot(struct xattr *xattrs,
  * care of the common case and reduces the amount of
  * text involved.
  */
-#define LSM_HOOK_INIT(HEAD, HOOK) \
-	{ .head = &security_hook_heads.HEAD, .hook = { .HEAD = HOOK } }
-
-extern struct security_hook_heads security_hook_heads;
-extern char *lsm_names;
+#define LSM_HOOK_INIT(NAME, HOOK)			\
+	{						\
+		.scalls = static_calls_table.NAME,	\
+		.hook = { .NAME = HOOK }		\
+	}
 
 extern void security_add_hooks(struct security_hook_list *hooks, int count,
 			       const struct lsm_id *lsmid);
@@ -137,9 +157,6 @@ struct lsm_info {
 	struct lsm_blob_sizes *blobs; /* Optional: for blob sharing. */
 };
 
-extern struct lsm_info __start_lsm_info[], __end_lsm_info[];
-extern struct lsm_info __start_early_lsm_info[], __end_early_lsm_info[];
-
 #define DEFINE_LSM(lsm)							\
 	static struct lsm_info __lsm_##lsm				\
 		__used __section(".lsm_info.init")			\
@@ -150,6 +167,28 @@ extern struct lsm_info __start_early_lsm_info[], __end_early_lsm_info[];
 		__used __section(".early_lsm_info.init")		\
 		__aligned(sizeof(unsigned long))
 
-extern int lsm_inode_alloc(struct inode *inode);
+/* DO NOT tamper with these variables outside of the LSM framework */
+extern char *lsm_names;
+extern struct lsm_static_calls_table static_calls_table __ro_after_init;
+extern struct lsm_info __start_lsm_info[], __end_lsm_info[];
+extern struct lsm_info __start_early_lsm_info[], __end_early_lsm_info[];
+
+/**
+ * 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)++];
+}
 
 #endif /* ! __LINUX_LSM_HOOKS_H */