keys: sparse: Fix key_fs[ug]id_changed()

Sparse warnings are incurred by key_fs[ug]id_changed() due to unprotected
accesses of tsk->cred, which is marked __rcu.

Fix this by passing the new cred struct to these functions from
commit_creds() rather than the task pointer.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>

3 files changed, 16 insertions, 18 deletions

diff --git a/include/linux/key.h b/include/linux/key.h
index 7099985e35a9..1f09aad1c98c 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -402,8 +402,8 @@ extern struct ctl_table key_sysctls[];
  * the userspace interface
  */
 extern int install_thread_keyring_to_cred(struct cred *cred);
-extern void key_fsuid_changed(struct task_struct *tsk);
-extern void key_fsgid_changed(struct task_struct *tsk);
+extern void key_fsuid_changed(struct cred *new_cred);
+extern void key_fsgid_changed(struct cred *new_cred);
 extern void key_init(void);
 
 #else /* CONFIG_KEYS */
@@ -418,8 +418,8 @@ extern void key_init(void);
 #define make_key_ref(k, p)              NULL
 #define key_ref_to_ptr(k)               NULL
 #define is_key_possessed(k)             0
-#define key_fsuid_changed(t)            do { } while(0)
-#define key_fsgid_changed(t)            do { } while(0)
+#define key_fsuid_changed(c)            do { } while(0)
+#define key_fsgid_changed(c)            do { } while(0)
 #define key_init()                      do { } while(0)
 
 #endif /* CONFIG_KEYS */
diff --git a/kernel/cred.c b/kernel/cred.c
index 45d77284aed0..3bd40de9e192 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -455,9 +455,9 @@ int commit_creds(struct cred *new)
 
         /* alter the thread keyring */
         if (!uid_eq(new->fsuid, old->fsuid))
-                key_fsuid_changed(task);
+                key_fsuid_changed(new);
         if (!gid_eq(new->fsgid, old->fsgid))
-                key_fsgid_changed(task);
+                key_fsgid_changed(new);
 
         /* do it
          * RLIMIT_NPROC limits on user->processes have already been checked
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index f05f7125a7d5..ba5d3172cafe 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -293,28 +293,26 @@ static int install_session_keyring(struct key *keyring)
 /*
  * Handle the fsuid changing.
  */
-void key_fsuid_changed(struct task_struct *tsk)
+void key_fsuid_changed(struct cred *new_cred)
 {
         /* update the ownership of the thread keyring */
-        BUG_ON(!tsk->cred);
-        if (tsk->cred->thread_keyring) {
-                down_write(&tsk->cred->thread_keyring->sem);
-                tsk->cred->thread_keyring->uid = tsk->cred->fsuid;
-                up_write(&tsk->cred->thread_keyring->sem);
+        if (new_cred->thread_keyring) {
+                down_write(&new_cred->thread_keyring->sem);
+                new_cred->thread_keyring->uid = new_cred->fsuid;
+                up_write(&new_cred->thread_keyring->sem);
         }
 }
 
 /*
  * Handle the fsgid changing.
  */
-void key_fsgid_changed(struct task_struct *tsk)
+void key_fsgid_changed(struct cred *new_cred)
 {
         /* update the ownership of the thread keyring */
-        BUG_ON(!tsk->cred);
-        if (tsk->cred->thread_keyring) {
-                down_write(&tsk->cred->thread_keyring->sem);
-                tsk->cred->thread_keyring->gid = tsk->cred->fsgid;
-                up_write(&tsk->cred->thread_keyring->sem);
+        if (new_cred->thread_keyring) {
+                down_write(&new_cred->thread_keyring->sem);
+                new_cred->thread_keyring->gid = new_cred->fsgid;
+                up_write(&new_cred->thread_keyring->sem);
         }
 }