keys: allow clients to set key perms in key_create_or_update()

The key_create_or_update() function provided by the keyring code has a default
set of permissions that are always applied to the key when created.  This
might not be desirable to all clients.

Here's a patch that adds a "perm" parameter to the function to address this,
which can be set to KEY_PERM_UNDEF to revert to the current behaviour.

Signed-off-by: Arun Raghavan <arunsr@cse.iitk.ac.in>
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Satyam Sharma <ssatyam@cse.iitk.ac.in>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 15 insertions, 9 deletions

diff --git a/include/linux/key.h b/include/linux/key.h
index 163f864b6bd4..8b0bd3393abc 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -67,6 +67,8 @@ struct key;
 #define KEY_OTH_SETATTR 0x00000020
 #define KEY_OTH_ALL     0x0000003f
 
+#define KEY_PERM_UNDEF  0xffffffff
+
 struct seq_file;
 struct user_struct;
 struct signal_struct;
@@ -232,6 +234,7 @@ extern key_ref_t key_create_or_update(key_ref_t keyring,
                                       const char *description,
                                       const void *payload,
                                       size_t plen,
+                                      key_perm_t perm,
                                       unsigned long flags);
 
 extern int key_update(key_ref_t key,
diff --git a/security/keys/key.c b/security/keys/key.c
index 654d23baf352..d98c61953be6 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -757,11 +757,11 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
                                const char *description,
                                const void *payload,
                                size_t plen,
+                               key_perm_t perm,
                                unsigned long flags)
 {
         struct key_type *ktype;
         struct key *keyring, *key = NULL;
-        key_perm_t perm;
         key_ref_t key_ref;
         int ret;
 
@@ -806,15 +806,17 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
                         goto found_matching_key;
         }
 
-        /* decide on the permissions we want */
-        perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
-        perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
+        /* if the client doesn't provide, decide on the permissions we want */
+        if (perm == KEY_PERM_UNDEF) {
+                perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
+                perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
 
-        if (ktype->read)
-                perm |= KEY_POS_READ | KEY_USR_READ;
+                if (ktype->read)
+                        perm |= KEY_POS_READ | KEY_USR_READ;
 
-        if (ktype == &key_type_keyring || ktype->update)
-                perm |= KEY_USR_WRITE;
+                if (ktype == &key_type_keyring || ktype->update)
+                        perm |= KEY_USR_WRITE;
+        }
 
         /* allocate a new key */
         key = key_alloc(ktype, description, current->fsuid, current->fsgid,
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 56e963b700b9..993be634a5ef 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -112,7 +112,8 @@ asmlinkage long sys_add_key(const char __user *_type,
         /* create or update the requested key and add it to the target
          * keyring */
         key_ref = key_create_or_update(keyring_ref, type, description,
-                                       payload, plen, KEY_ALLOC_IN_QUOTA);
+                                       payload, plen, KEY_PERM_UNDEF,
+                                       KEY_ALLOC_IN_QUOTA);
         if (!IS_ERR(key_ref)) {
                 ret = key_ref_to_ptr(key_ref)->serial;
                 key_ref_put(key_ref);