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authorDavid Howells <dhowells@redhat.com>2010-04-30 14:32:23 +0100
committerJames Morris <jmorris@namei.org>2010-05-05 23:50:24 +1000
commit896903c2f5f79f029388f033a00c3b813bc91201 (patch)
treef679108ab3c9cda3f5e1f6240afccc6ee3984406 /security
parentf0641cba7729e5e14f82d2eedc398103f5fa31b1 (diff)
downloadlinux-2.6.34-ux500-896903c2f5f79f029388f033a00c3b813bc91201.tar.gz
KEYS: call_sbin_request_key() must write lock keyrings before modifying them
call_sbin_request_key() creates a keyring and then attempts to insert a link to the authorisation key into that keyring, but does so without holding a write lock on the keyring semaphore. It will normally get away with this because it hasn't told anyone that the keyring exists yet. The new keyring, however, has had its serial number published, which means it can be accessed directly by that handle. This was found by a previous patch that adds RCU lockdep checks to the code that reads the keyring payload pointer, which includes a check that the keyring semaphore is actually locked. Without this patch, the following command: keyctl request2 user b a @s will provoke the following lockdep warning is displayed in dmesg: =================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- security/keys/keyring.c:727 invoked rcu_dereference_check() without protection! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 0 2 locks held by keyctl/2076: #0: (key_types_sem){.+.+.+}, at: [<ffffffff811a5b29>] key_type_lookup+0x1c/0x71 #1: (keyring_serialise_link_sem){+.+.+.}, at: [<ffffffff811a6d1e>] __key_link+0x4d/0x3c5 stack backtrace: Pid: 2076, comm: keyctl Not tainted 2.6.34-rc6-cachefs #54 Call Trace: [<ffffffff81051fdc>] lockdep_rcu_dereference+0xaa/0xb2 [<ffffffff811a6d1e>] ? __key_link+0x4d/0x3c5 [<ffffffff811a6e6f>] __key_link+0x19e/0x3c5 [<ffffffff811a5952>] ? __key_instantiate_and_link+0xb1/0xdc [<ffffffff811a59bf>] ? key_instantiate_and_link+0x42/0x5f [<ffffffff811aa0dc>] call_sbin_request_key+0xe7/0x33b [<ffffffff8139376a>] ? mutex_unlock+0x9/0xb [<ffffffff811a5952>] ? __key_instantiate_and_link+0xb1/0xdc [<ffffffff811a59bf>] ? key_instantiate_and_link+0x42/0x5f [<ffffffff811aa6fa>] ? request_key_auth_new+0x1c2/0x23c [<ffffffff810aaf15>] ? cache_alloc_debugcheck_after+0x108/0x173 [<ffffffff811a9d00>] ? request_key_and_link+0x146/0x300 [<ffffffff810ac568>] ? kmem_cache_alloc+0xe1/0x118 [<ffffffff811a9e45>] request_key_and_link+0x28b/0x300 [<ffffffff811a89ac>] sys_request_key+0xf7/0x14a [<ffffffff81052c0b>] ? trace_hardirqs_on_caller+0x10c/0x130 [<ffffffff81394fb9>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff81001eeb>] system_call_fastpath+0x16/0x1b Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to 'security')
-rw-r--r--security/keys/request_key.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index d737cea5347..d8c1a6a0fb0 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -94,7 +94,7 @@ static int call_sbin_request_key(struct key_construction *cons,
}
/* attach the auth key to the session keyring */
- ret = __key_link(keyring, authkey);
+ ret = key_link(keyring, authkey);
if (ret < 0)
goto error_link;