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authorDavid Howells <dhowells@redhat.com>2005-06-23 22:00:49 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-24 00:05:18 -0700
commit76d8aeabfeb1c42641a81c44280177b9a08670d8 (patch)
tree0a584439bb44e440717aa77a1398ba9eea24a137 /security/keys/keyctl.c
parent7286aa9b9ab35f20b1ff16d867f4535701df99b5 (diff)
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[PATCH] keys: Discard key spinlock and use RCU for key payload
The attached patch changes the key implementation in a number of ways: (1) It removes the spinlock from the key structure. (2) The key flags are now accessed using atomic bitops instead of write-locking the key spinlock and using C bitwise operators. The three instantiation flags are dealt with with the construction semaphore held during the request_key/instantiate/negate sequence, thus rendering the spinlock superfluous. The key flags are also now bit numbers not bit masks. (3) The key payload is now accessed using RCU. This permits the recursive keyring search algorithm to be simplified greatly since no locks need be taken other than the usual RCU preemption disablement. Searching now does not require any locks or semaphores to be held; merely that the starting keyring be pinned. (4) The keyring payload now includes an RCU head so that it can be disposed of by call_rcu(). This requires that the payload be copied on unlink to prevent introducing races in copy-down vs search-up. (5) The user key payload is now a structure with the data following it. It includes an RCU head like the keyring payload and for the same reason. It also contains a data length because the data length in the key may be changed on another CPU whilst an RCU protected read is in progress on the payload. This would then see the supposed RCU payload and the on-key data length getting out of sync. I'm tempted to drop the key's datalen entirely, except that it's used in conjunction with quota management and so is a little tricky to get rid of. (6) Update the keys documentation. Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'security/keys/keyctl.c')
-rw-r--r--security/keys/keyctl.c23
1 files changed, 7 insertions, 16 deletions
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index dc0011b3fac..cedb7326de2 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -728,7 +728,6 @@ long keyctl_chown_key(key_serial_t id, uid_t uid, gid_t gid)
/* make the changes with the locks held to prevent chown/chown races */
ret = -EACCES;
down_write(&key->sem);
- write_lock(&key->lock);
if (!capable(CAP_SYS_ADMIN)) {
/* only the sysadmin can chown a key to some other UID */
@@ -755,7 +754,6 @@ long keyctl_chown_key(key_serial_t id, uid_t uid, gid_t gid)
ret = 0;
no_access:
- write_unlock(&key->lock);
up_write(&key->sem);
key_put(key);
error:
@@ -784,26 +782,19 @@ long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
goto error;
}
- /* make the changes with the locks held to prevent chown/chmod
- * races */
+ /* make the changes with the locks held to prevent chown/chmod races */
ret = -EACCES;
down_write(&key->sem);
- write_lock(&key->lock);
- /* if we're not the sysadmin, we can only chmod a key that we
- * own */
- if (!capable(CAP_SYS_ADMIN) && key->uid != current->fsuid)
- goto no_access;
-
- /* changing the permissions mask */
- key->perm = perm;
- ret = 0;
+ /* if we're not the sysadmin, we can only change a key that we own */
+ if (capable(CAP_SYS_ADMIN) || key->uid == current->fsuid) {
+ key->perm = perm;
+ ret = 0;
+ }
- no_access:
- write_unlock(&key->lock);
up_write(&key->sem);
key_put(key);
- error:
+error:
return ret;
} /* end keyctl_setperm_key() */