apparmor: drop cred_ctx and reference the label directly

With the task domain change information now stored in the task->security
context, the cred->security context only stores the label. We can get
rid of the cred_ctx and directly reference the label, removing a layer
of indirection, and unneeded extra allocations.

Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/context.c

@@ -13,11 +13,9 @@
  * License.
  *
  *
- * AppArmor sets confinement on every task, via the the aa_cred_ctx and
- * the aa_cred_ctx.label, both of which are required and are not allowed
- * to be NULL.  The aa_cred_ctx is not reference counted and is unique
- * to each cred (which is reference count).  The label pointed to by
- * the cred_ctx is reference counted.
+ * AppArmor sets confinement on every task, via the cred_label() which
+ * is required and are not allowed to be NULL.  The cred_label is
+ * reference counted.
  *
  * TODO
  * If a task uses change_hat it currently does not return to the old
@@ -29,40 +27,6 @@
 #include "include/context.h"
 #include "include/policy.h"
 
-/**
- * aa_alloc_cred_ctx - allocate a new cred_ctx
- * @flags: gfp flags for allocation
- *
- * Returns: allocated buffer or NULL on failure
- */
-struct aa_cred_ctx *aa_alloc_cred_ctx(gfp_t flags)
-{
-	return kzalloc(sizeof(struct aa_cred_ctx), flags);
-}
-
-/**
- * aa_free_cred_ctx - free a cred_ctx
- * @ctx: cred_ctx to free (MAYBE NULL)
- */
-void aa_free_cred_ctx(struct aa_cred_ctx *ctx)
-{
-	if (ctx) {
-		aa_put_label(ctx->label);
-
-		kzfree(ctx);
-	}
-}
-
-/**
- * aa_dup_cred_ctx - duplicate a task context, incrementing reference counts
- * @new: a blank task context      (NOT NULL)
- * @old: the task context to copy  (NOT NULL)
- */
-void aa_dup_cred_ctx(struct aa_cred_ctx *new, const struct aa_cred_ctx *old)
-{
-	*new = *old;
-	aa_get_label(new->label);
-}
 
 /**
  * aa_get_task_label - Get another task's label
@@ -126,11 +90,12 @@ void aa_dup_task_ctx(struct aa_task_ctx *new, const struct aa_task_ctx *old)
  */
 int aa_replace_current_label(struct aa_label *label)
 {
-	struct aa_cred_ctx *ctx = current_cred_ctx();
+	struct aa_label *old = aa_current_raw_label();
 	struct cred *new;
+
 	AA_BUG(!label);
 
-	if (ctx->label == label)
+	if (old == label)
 		return 0;
 
 	if (current_cred() != current_real_cred())
@@ -140,22 +105,22 @@ int aa_replace_current_label(struct aa_label *label)
 	if (!new)
 		return -ENOMEM;
 
-	ctx = cred_ctx(new);
-	if (unconfined(label) || (labels_ns(ctx->label) != labels_ns(label)))
-		/* if switching to unconfined or a different label namespace
+	if (unconfined(label) || (labels_ns(old) != labels_ns(label)))
+		/*
+		 * if switching to unconfined or a different label namespace
 		 * clear out context state
 		 */
 		aa_clear_task_ctx_trans(current_task_ctx());
 
 	/*
-	 * be careful switching ctx->profile, when racing replacement it
-	 * is possible that ctx->profile->proxy->profile is the reference
-	 * keeping @profile valid, so make sure to get its reference before
-	 * dropping the reference on ctx->profile
+	 * be careful switching cred label, when racing replacement it
+	 * is possible that the cred labels's->proxy->label is the reference
+	 * keeping @label valid, so make sure to get its reference before
+	 * dropping the reference on the cred's label
 	 */
 	aa_get_label(label);
-	aa_put_label(ctx->label);
-	ctx->label = label;
+	aa_put_label(cred_label(new));
+	cred_label(new) = label;
 
 	commit_creds(new);
 	return 0;
@@ -193,26 +158,26 @@ int aa_set_current_hat(struct aa_label *label, u64 token)
 {
 	struct aa_task_ctx *tctx = current_task_ctx();
 	struct aa_cred_ctx *ctx;
-	struct cred *new = prepare_creds();
+	struct cred *new;
 
+	new = prepare_creds();
 	if (!new)
 		return -ENOMEM;
 	AA_BUG(!label);
 
-	ctx = cred_ctx(new);
 	if (!tctx->previous) {
 		/* transfer refcount */
-		tctx->previous = ctx->label;
+		tctx->previous = cred_label(new);
 		tctx->token = token;
 	} else if (tctx->token == token) {
-		aa_put_label(ctx->label);
+		aa_put_label(cred_label(new));
 	} else {
 		/* previous_profile && ctx->token != token */
 		abort_creds(new);
 		return -EACCES;
 	}
 
-	ctx->label = aa_get_newest_label(label);
+	cred_label(new) = aa_get_newest_label(label);
 	/* clear exec on switching context */
 	aa_put_label(tctx->onexec);
 	tctx->onexec = NULL;
@@ -233,7 +198,6 @@ int aa_set_current_hat(struct aa_label *label, u64 token)
 int aa_restore_previous_label(u64 token)
 {
 	struct aa_task_ctx *tctx = current_task_ctx();
-	struct aa_cred_ctx *ctx;
 	struct cred *new;
 
 	if (tctx->token != token)
@@ -245,11 +209,10 @@ int aa_restore_previous_label(u64 token)
 	new = prepare_creds();
 	if (!new)
 		return -ENOMEM;
-	ctx = cred_ctx(new);
 
-	aa_put_label(ctx->label);
-	ctx->label = aa_get_newest_label(tctx->previous);
-	AA_BUG(!ctx->label);
+	aa_put_label(cred_label(new));
+	cred_label(new) = aa_get_newest_label(tctx->previous);
+	AA_BUG(!cred_label(new));
 	/* clear exec && prev information when restoring to previous context */
 	aa_clear_task_ctx_trans(tctx);
 

security/apparmor/domain.c

@@ -779,7 +779,6 @@ static struct aa_label *handle_onexec(struct aa_label *label,
  */
 int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 {
-	struct aa_cred_ctx *ctx;
 	struct aa_task_ctx *tctx;
 	struct aa_label *label, *new = NULL;
 	struct aa_profile *profile;
@@ -795,12 +794,11 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 	if (bprm->called_set_creds)
 		return 0;
 
-	ctx = cred_ctx(bprm->cred);
 	tctx = current_task_ctx();
-	AA_BUG(!ctx);
+	AA_BUG(!cred_label(bprm->cred));
 	AA_BUG(!tctx);
 
-	label = aa_get_newest_label(ctx->label);
+	label = aa_get_newest_label(cred_label(bprm->cred));
 
 	/* buffer freed below, name is pointer into buffer */
 	get_buffers(buffer);
@@ -856,9 +854,9 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 		}
 		bprm->per_clear |= PER_CLEAR_ON_SETID;
 	}
-	aa_put_label(ctx->label);
-	/* transfer reference, released when ctx is freed */
-	ctx->label = new;
+	aa_put_label(cred_label(bprm->cred));
+	/* transfer reference, released when cred is freed */
+	cred_label(bprm->cred) = new;
 
 done:
 	aa_put_label(label);
@@ -1049,7 +1047,6 @@ build:
 int aa_change_hat(const char *hats[], int count, u64 token, int flags)
 {
 	const struct cred *cred;
-	struct aa_cred_ctx *ctx;
 	struct aa_task_ctx *tctx;
 	struct aa_label *label, *previous, *new = NULL, *target = NULL;
 	struct aa_profile *profile;
@@ -1070,7 +1067,6 @@ int aa_change_hat(const char *hats[], int count, u64 token, int flags)
 
 	/* released below */
 	cred = get_current_cred();
-	ctx = cred_ctx(cred);
 	tctx = current_task_ctx();
 	label = aa_get_newest_cred_label(cred);
 	previous = aa_get_newest_label(tctx->previous);

security/apparmor/include/context.h

@@ -22,21 +22,11 @@
 #include "label.h"
 #include "policy_ns.h"
 
-#define cred_ctx(X) ((X)->security)
-#define current_cred_ctx() cred_ctx(current_cred())
-
 #define task_ctx(X) ((X)->security)
 #define current_task_ctx() (task_ctx(current))
+#define cred_label(X) ((X)->security)
 
-/**
- * struct aa_cred_ctx - primary label for confined tasks
- * @label: the current label   (NOT NULL)
- */
-struct aa_cred_ctx {
-	struct aa_label *label;
-};
-
-/**
+/*
  * struct aa_task_ctx - information for current task label change
  * @onexec: profile to transition to on next exec  (MAY BE NULL)
  * @previous: profile the task may return to     (MAY BE NULL)
@@ -48,10 +38,6 @@ struct aa_task_ctx {
 	u64 token;
 };
 
-struct aa_cred_ctx *aa_alloc_cred_ctx(gfp_t flags);
-void aa_free_cred_ctx(struct aa_cred_ctx *ctx);
-void aa_dup_cred_ctx(struct aa_cred_ctx *new, const struct aa_cred_ctx *old);
-
 struct aa_task_ctx *aa_alloc_task_ctx(gfp_t flags);
 void aa_free_task_ctx(struct aa_task_ctx *ctx);
 void aa_dup_task_ctx(struct aa_task_ctx *new, const struct aa_task_ctx *old);
@@ -73,10 +59,10 @@ struct aa_label *aa_get_task_label(struct task_struct *task);
  */
 static inline struct aa_label *aa_cred_raw_label(const struct cred *cred)
 {
-	struct aa_cred_ctx *ctx = cred_ctx(cred);
+	struct aa_label *label = cred_label(cred);
 
-	AA_BUG(!ctx || !ctx->label);
-	return ctx->label;
+	AA_BUG(!label);
+	return label;
 }
 
 /**

security/apparmor/lsm.c

@@ -51,12 +51,12 @@ DEFINE_PER_CPU(struct aa_buffers, aa_buffers);
  */
 
 /*
- * free the associated aa_cred_ctx and put its labels
+ * put the associated labels
  */
 static void apparmor_cred_free(struct cred *cred)
 {
-	aa_free_cred_ctx(cred_ctx(cred));
-	cred_ctx(cred) = NULL;
+	aa_put_label(cred_label(cred));
+	cred_label(cred) = NULL;
 }
 
 /*
@@ -64,30 +64,17 @@ static void apparmor_cred_free(struct cred *cred)
  */
 static int apparmor_cred_alloc_blank(struct cred *cred, gfp_t gfp)
 {
-	/* freed by apparmor_cred_free */
-	struct aa_cred_ctx *ctx = aa_alloc_cred_ctx(gfp);
-
-	if (!ctx)
-		return -ENOMEM;
-
-	cred_ctx(cred) = ctx;
+	cred_label(cred) = NULL;
 	return 0;
 }
 
 /*
- * prepare new aa_cred_ctx for modification by prepare_cred block
+ * prepare new cred label for modification by prepare_cred block
  */
 static int apparmor_cred_prepare(struct cred *new, const struct cred *old,
 				 gfp_t gfp)
 {
-	/* freed by apparmor_cred_free */
-	struct aa_cred_ctx *ctx = aa_alloc_cred_ctx(gfp);
-
-	if (!ctx)
-		return -ENOMEM;
-
-	aa_dup_cred_ctx(ctx, cred_ctx(old));
-	cred_ctx(new) = ctx;
+	cred_label(new) = aa_get_newest_label(cred_label(old));
 	return 0;
 }
 
@@ -96,10 +83,7 @@ static int apparmor_cred_prepare(struct cred *new, const struct cred *old,
  */
 static void apparmor_cred_transfer(struct cred *new, const struct cred *old)
 {
-	const struct aa_cred_ctx *old_ctx = cred_ctx(old);
-	struct aa_cred_ctx *new_ctx = cred_ctx(new);
-
-	aa_dup_cred_ctx(new_ctx, old_ctx);
+	cred_label(new) = aa_get_newest_label(cred_label(old));
 }
 
 static void apparmor_task_free(struct task_struct *task)
@@ -599,11 +583,10 @@ static int apparmor_getprocattr(struct task_struct *task, char *name,
 	/* released below */
 	const struct cred *cred = get_task_cred(task);
 	struct aa_task_ctx *tctx = current_task_ctx();
-	struct aa_cred_ctx *ctx = cred_ctx(cred);
 	struct aa_label *label = NULL;
 
 	if (strcmp(name, "current") == 0)
-		label = aa_get_newest_label(ctx->label);
+		label = aa_get_newest_label(cred_label(cred));
 	else if (strcmp(name, "prev") == 0  && tctx->previous)
 		label = aa_get_newest_label(tctx->previous);
 	else if (strcmp(name, "exec") == 0 && tctx->onexec)
@@ -700,11 +683,11 @@ fail:
 static void apparmor_bprm_committing_creds(struct linux_binprm *bprm)
 {
 	struct aa_label *label = aa_current_raw_label();
-	struct aa_cred_ctx *new_ctx = cred_ctx(bprm->cred);
+	struct aa_label *new_label = cred_label(bprm->cred);
 
 	/* bail out if unconfined or not changing profile */
-	if ((new_ctx->label->proxy == label->proxy) ||
-	    (unconfined(new_ctx->label)))
+	if ((new_label->proxy == label->proxy) ||
+	    (unconfined(new_label)))
 		return;
 
 	aa_inherit_files(bprm->cred, current->files);
@@ -712,7 +695,7 @@ static void apparmor_bprm_committing_creds(struct linux_binprm *bprm)
 	current->pdeath_signal = 0;
 
 	/* reset soft limits and set hard limits for the new label */
-	__aa_transition_rlimits(label, new_ctx->label);
+	__aa_transition_rlimits(label, new_label);
 }
 
 /**
@@ -1050,26 +1033,16 @@ static int param_set_mode(const char *val, const struct kernel_param *kp)
 static int __init set_init_ctx(void)
 {
 	struct cred *cred = (struct cred *)current->real_cred;
-	struct aa_cred_ctx *ctx;
 	struct aa_task_ctx *tctx;
 
-	ctx = aa_alloc_cred_ctx(GFP_KERNEL);
-	if (!ctx)
-		goto fail_cred;
 	tctx = aa_alloc_task_ctx(GFP_KERNEL);
 	if (!tctx)
-		goto fail_task;
+		return -ENOMEM;
 
-	ctx->label = aa_get_label(ns_unconfined(root_ns));
-	cred_ctx(cred) = ctx;
+	cred_label(cred) = aa_get_label(ns_unconfined(root_ns));
 	task_ctx(current) = tctx;
 
 	return 0;
-
-fail_task:
-	aa_free_cred_ctx(ctx);
-fail_cred:
-	return -ENOMEM;
 }
 
 static void destroy_buffers(void)