1 files changed, 244 insertions, 6 deletions

diff --git a/kernel/cred.c b/kernel/cred.c
index 1bb4d7e5d616..24dd2f5104b1 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -18,6 +18,18 @@
 #include <linux/cn_proc.h>
 #include "cred-internals.h"
 
+#if 0
+#define kdebug(FMT, ...) \
+        printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
+#else
+static inline __attribute__((format(printf, 1, 2)))
+void no_printk(const char *fmt, ...)
+{
+}
+#define kdebug(FMT, ...) \
+        no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
+#endif
+
 static struct kmem_cache *cred_jar;
 
 /*
@@ -36,6 +48,10 @@ static struct thread_group_cred init_tgcred = {
  */
 struct cred init_cred = {
         .usage                  = ATOMIC_INIT(4),
+#ifdef CONFIG_DEBUG_CREDENTIALS
+        .subscribers            = ATOMIC_INIT(2),
+        .magic                  = CRED_MAGIC,
+#endif
         .securebits             = SECUREBITS_DEFAULT,
         .cap_inheritable        = CAP_INIT_INH_SET,
         .cap_permitted          = CAP_FULL_SET,
@@ -48,6 +64,31 @@ struct cred init_cred = {
 #endif
 };
 
+static inline void set_cred_subscribers(struct cred *cred, int n)
+{
+#ifdef CONFIG_DEBUG_CREDENTIALS
+        atomic_set(&cred->subscribers, n);
+#endif
+}
+
+static inline int read_cred_subscribers(const struct cred *cred)
+{
+#ifdef CONFIG_DEBUG_CREDENTIALS
+        return atomic_read(&cred->subscribers);
+#else
+        return 0;
+#endif
+}
+
+static inline void alter_cred_subscribers(const struct cred *_cred, int n)
+{
+#ifdef CONFIG_DEBUG_CREDENTIALS
+        struct cred *cred = (struct cred *) _cred;
+
+        atomic_add(n, &cred->subscribers);
+#endif
+}
+
 /*
  * Dispose of the shared task group credentials
  */
@@ -85,9 +126,22 @@ static void put_cred_rcu(struct rcu_head *rcu)
 {
         struct cred *cred = container_of(rcu, struct cred, rcu);
 
+        kdebug("put_cred_rcu(%p)", cred);
+
+#ifdef CONFIG_DEBUG_CREDENTIALS
+        if (cred->magic != CRED_MAGIC_DEAD ||
+            atomic_read(&cred->usage) != 0 ||
+            read_cred_subscribers(cred) != 0)
+                panic("CRED: put_cred_rcu() sees %p with"
+                      " mag %x, put %p, usage %d, subscr %d\n",
+                      cred, cred->magic, cred->put_addr,
+                      atomic_read(&cred->usage),
+                      read_cred_subscribers(cred));
+#else
         if (atomic_read(&cred->usage) != 0)
                 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
                       cred, atomic_read(&cred->usage));
+#endif
 
         security_cred_free(cred);
         key_put(cred->thread_keyring);
@@ -106,12 +160,47 @@ static void put_cred_rcu(struct rcu_head *rcu)
  */
 void __put_cred(struct cred *cred)
 {
+        kdebug("__put_cred(%p{%d,%d})", cred,
+               atomic_read(&cred->usage),
+               read_cred_subscribers(cred));
+
         BUG_ON(atomic_read(&cred->usage) != 0);
+#ifdef CONFIG_DEBUG_CREDENTIALS
+        BUG_ON(read_cred_subscribers(cred) != 0);
+        cred->magic = CRED_MAGIC_DEAD;
+        cred->put_addr = __builtin_return_address(0);
+#endif
+        BUG_ON(cred == current->cred);
+        BUG_ON(cred == current->real_cred);
 
         call_rcu(&cred->rcu, put_cred_rcu);
 }
 EXPORT_SYMBOL(__put_cred);
 
+/*
+ * Clean up a task's credentials when it exits
+ */
+void exit_creds(struct task_struct *tsk)
+{
+        struct cred *cred;
+
+        kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
+               atomic_read(&tsk->cred->usage),
+               read_cred_subscribers(tsk->cred));
+
+        cred = (struct cred *) tsk->real_cred;
+        tsk->real_cred = NULL;
+        validate_creds(cred);
+        alter_cred_subscribers(cred, -1);
+        put_cred(cred);
+
+        cred = (struct cred *) tsk->cred;
+        tsk->cred = NULL;
+        validate_creds(cred);
+        alter_cred_subscribers(cred, -1);
+        put_cred(cred);
+}
+
 /**
  * prepare_creds - Prepare a new set of credentials for modification
  *
@@ -132,16 +221,19 @@ struct cred *prepare_creds(void)
         const struct cred *old;
         struct cred *new;
 
-        BUG_ON(atomic_read(&task->real_cred->usage) < 1);
+        validate_process_creds();
 
         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
         if (!new)
                 return NULL;
 
+        kdebug("prepare_creds() alloc %p", new);
+
         old = task->cred;
         memcpy(new, old, sizeof(struct cred));
 
         atomic_set(&new->usage, 1);
+        set_cred_subscribers(new, 0);
         get_group_info(new->group_info);
         get_uid(new->user);
 
@@ -157,6 +249,7 @@ struct cred *prepare_creds(void)
 
         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
                 goto error;
+        validate_creds(new);
         return new;
 
 error:
@@ -229,9 +322,12 @@ struct cred *prepare_usermodehelper_creds(void)
         if (!new)
                 return NULL;
 
+        kdebug("prepare_usermodehelper_creds() alloc %p", new);
+
         memcpy(new, &init_cred, sizeof(struct cred));
 
         atomic_set(&new->usage, 1);
+        set_cred_subscribers(new, 0);
         get_group_info(new->group_info);
         get_uid(new->user);
 
@@ -250,6 +346,7 @@ struct cred *prepare_usermodehelper_creds(void)
 #endif
         if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)
                 goto error;
+        validate_creds(new);
 
         BUG_ON(atomic_read(&new->usage) != 1);
         return new;
@@ -286,6 +383,10 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags)
             ) {
                 p->real_cred = get_cred(p->cred);
                 get_cred(p->cred);
+                alter_cred_subscribers(p->cred, 2);
+                kdebug("share_creds(%p{%d,%d})",
+                       p->cred, atomic_read(&p->cred->usage),
+                       read_cred_subscribers(p->cred));
                 atomic_inc(&p->cred->user->processes);
                 return 0;
         }
@@ -331,6 +432,8 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags)
 
         atomic_inc(&new->user->processes);
         p->cred = p->real_cred = get_cred(new);
+        alter_cred_subscribers(new, 2);
+        validate_creds(new);
         return 0;
 
 error_put:
@@ -355,13 +458,20 @@ error_put:
 int commit_creds(struct cred *new)
 {
         struct task_struct *task = current;
-        const struct cred *old;
+        const struct cred *old = task->real_cred;
 
-        BUG_ON(task->cred != task->real_cred);
-        BUG_ON(atomic_read(&task->real_cred->usage) < 2);
+        kdebug("commit_creds(%p{%d,%d})", new,
+               atomic_read(&new->usage),
+               read_cred_subscribers(new));
+
+        BUG_ON(task->cred != old);
+#ifdef CONFIG_DEBUG_CREDENTIALS
+        BUG_ON(read_cred_subscribers(old) < 2);
+        validate_creds(old);
+        validate_creds(new);
+#endif
         BUG_ON(atomic_read(&new->usage) < 1);
 
-        old = task->real_cred;
         security_commit_creds(new, old);
 
         get_cred(new); /* we will require a ref for the subj creds too */
@@ -390,12 +500,14 @@ int commit_creds(struct cred *new)
          *   cheaply with the new uid cache, so if it matters
          *   we should be checking for it.  -DaveM
          */
+        alter_cred_subscribers(new, 2);
         if (new->user != old->user)
                 atomic_inc(&new->user->processes);
         rcu_assign_pointer(task->real_cred, new);
         rcu_assign_pointer(task->cred, new);
         if (new->user != old->user)
                 atomic_dec(&old->user->processes);
+        alter_cred_subscribers(old, -2);
 
         sched_switch_user(task);
 
@@ -428,6 +540,13 @@ EXPORT_SYMBOL(commit_creds);
  */
 void abort_creds(struct cred *new)
 {
+        kdebug("abort_creds(%p{%d,%d})", new,
+               atomic_read(&new->usage),
+               read_cred_subscribers(new));
+
+#ifdef CONFIG_DEBUG_CREDENTIALS
+        BUG_ON(read_cred_subscribers(new) != 0);
+#endif
         BUG_ON(atomic_read(&new->usage) < 1);
         put_cred(new);
 }
@@ -444,7 +563,20 @@ const struct cred *override_creds(const struct cred *new)
 {
         const struct cred *old = current->cred;
 
-        rcu_assign_pointer(current->cred, get_cred(new));
+        kdebug("override_creds(%p{%d,%d})", new,
+               atomic_read(&new->usage),
+               read_cred_subscribers(new));
+
+        validate_creds(old);
+        validate_creds(new);
+        get_cred(new);
+        alter_cred_subscribers(new, 1);
+        rcu_assign_pointer(current->cred, new);
+        alter_cred_subscribers(old, -1);
+
+        kdebug("override_creds() = %p{%d,%d}", old,
+               atomic_read(&old->usage),
+               read_cred_subscribers(old));
         return old;
 }
 EXPORT_SYMBOL(override_creds);
@@ -460,7 +592,15 @@ void revert_creds(const struct cred *old)
 {
         const struct cred *override = current->cred;
 
+        kdebug("revert_creds(%p{%d,%d})", old,
+               atomic_read(&old->usage),
+               read_cred_subscribers(old));
+
+        validate_creds(old);
+        validate_creds(override);
+        alter_cred_subscribers(old, 1);
         rcu_assign_pointer(current->cred, old);
+        alter_cred_subscribers(override, -1);
         put_cred(override);
 }
 EXPORT_SYMBOL(revert_creds);
@@ -502,11 +642,15 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
         if (!new)
                 return NULL;
 
+        kdebug("prepare_kernel_cred() alloc %p", new);
+
         if (daemon)
                 old = get_task_cred(daemon);
         else
                 old = get_cred(&init_cred);
 
+        validate_creds(old);
+
         *new = *old;
         get_uid(new->user);
         get_group_info(new->group_info);
@@ -526,7 +670,9 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
                 goto error;
 
         atomic_set(&new->usage, 1);
+        set_cred_subscribers(new, 0);
         put_cred(old);
+        validate_creds(new);
         return new;
 
 error:
@@ -589,3 +735,95 @@ int set_create_files_as(struct cred *new, struct inode *inode)
         return security_kernel_create_files_as(new, inode);
 }
 EXPORT_SYMBOL(set_create_files_as);
+
+#ifdef CONFIG_DEBUG_CREDENTIALS
+
+/*
+ * dump invalid credentials
+ */
+static void dump_invalid_creds(const struct cred *cred, const char *label,
+                               const struct task_struct *tsk)
+{
+        printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
+               label, cred,
+               cred == &init_cred ? "[init]" : "",
+               cred == tsk->real_cred ? "[real]" : "",
+               cred == tsk->cred ? "[eff]" : "");
+        printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
+               cred->magic, cred->put_addr);
+        printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
+               atomic_read(&cred->usage),
+               read_cred_subscribers(cred));
+        printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
+               cred->uid, cred->euid, cred->suid, cred->fsuid);
+        printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
+               cred->gid, cred->egid, cred->sgid, cred->fsgid);
+#ifdef CONFIG_SECURITY
+        printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
+        if ((unsigned long) cred->security >= PAGE_SIZE &&
+            (((unsigned long) cred->security & 0xffffff00) !=
+             (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
+                printk(KERN_ERR "CRED: ->security {%x, %x}\n",
+                       ((u32*)cred->security)[0],
+                       ((u32*)cred->security)[1]);
+#endif
+}
+
+/*
+ * report use of invalid credentials
+ */
+void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
+{
+        printk(KERN_ERR "CRED: Invalid credentials\n");
+        printk(KERN_ERR "CRED: At %s:%u\n", file, line);
+        dump_invalid_creds(cred, "Specified", current);
+        BUG();
+}
+EXPORT_SYMBOL(__invalid_creds);
+
+/*
+ * check the credentials on a process
+ */
+void __validate_process_creds(struct task_struct *tsk,
+                              const char *file, unsigned line)
+{
+        if (tsk->cred == tsk->real_cred) {
+                if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
+                             creds_are_invalid(tsk->cred)))
+                        goto invalid_creds;
+        } else {
+                if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
+                             read_cred_subscribers(tsk->cred) < 1 ||
+                             creds_are_invalid(tsk->real_cred) ||
+                             creds_are_invalid(tsk->cred)))
+                        goto invalid_creds;
+        }
+        return;
+
+invalid_creds:
+        printk(KERN_ERR "CRED: Invalid process credentials\n");
+        printk(KERN_ERR "CRED: At %s:%u\n", file, line);
+
+        dump_invalid_creds(tsk->real_cred, "Real", tsk);
+        if (tsk->cred != tsk->real_cred)
+                dump_invalid_creds(tsk->cred, "Effective", tsk);
+        else
+                printk(KERN_ERR "CRED: Effective creds == Real creds\n");
+        BUG();
+}
+EXPORT_SYMBOL(__validate_process_creds);
+
+/*
+ * check creds for do_exit()
+ */
+void validate_creds_for_do_exit(struct task_struct *tsk)
+{
+        kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
+               tsk->real_cred, tsk->cred,
+               atomic_read(&tsk->cred->usage),
+               read_cred_subscribers(tsk->cred));
+
+        __validate_process_creds(tsk, __FILE__, __LINE__);
+}
+
+#endif /* CONFIG_DEBUG_CREDENTIALS */