Messages in this thread | | | Subject | Re: [PATCH] KEYS: Fix an RCU warning | From | Eric Dumazet <> | Date | Tue, 20 Apr 2010 14:46:04 +0200 |
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Le mardi 20 avril 2010 à 11:25 +0100, David Howells a écrit : > Fix the following RCU warning: > > =================================================== > [ INFO: suspicious rcu_dereference_check() usage. ] > --------------------------------------------------- > security/keys/request_key.c:116 invoked rcu_dereference_check() without protection! > > other info that might help us debug this: > > > rcu_scheduler_active = 1, debug_locks = 0 > 1 lock held by keyctl/5372: > #0: (key_types_sem){.+.+.+}, at: [<ffffffff811a4e3d>] key_type_lookup+0x1c/0x70 > > stack backtrace: > Pid: 5372, comm: keyctl Not tainted 2.6.34-rc3-cachefs #150 > Call Trace: > [<ffffffff810515f8>] lockdep_rcu_dereference+0xaa/0xb2 > [<ffffffff811a9220>] call_sbin_request_key+0x156/0x2b6 > [<ffffffff811a4c66>] ? __key_instantiate_and_link+0xb1/0xdc > [<ffffffff811a4cd3>] ? key_instantiate_and_link+0x42/0x5f > [<ffffffff811a96b8>] ? request_key_auth_new+0x17b/0x1f3 > [<ffffffff811a8e00>] ? request_key_and_link+0x271/0x400 > [<ffffffff810aba6f>] ? kmem_cache_alloc+0xe1/0x118 > [<ffffffff811a8f1a>] request_key_and_link+0x38b/0x400 > [<ffffffff811a7b72>] sys_request_key+0xf7/0x14a > [<ffffffff81052227>] ? trace_hardirqs_on_caller+0x10c/0x130 > [<ffffffff81393f5c>] ? trace_hardirqs_on_thunk+0x3a/0x3f > [<ffffffff81001eeb>] system_call_fastpath+0x16/0x1b > > This was caused by doing: > > [root@andromeda ~]# keyctl newring fred @s > 539196288 > [root@andromeda ~]# keyctl request2 user a a 539196288 > request_key: Required key not available > > Signed-off-by: David Howells <dhowells@redhat.com> > --- >
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Thanks !
> security/keys/request_key.c | 13 ++++++++----- > 1 files changed, 8 insertions(+), 5 deletions(-) > > diff --git a/security/keys/request_key.c b/security/keys/request_key.c > index 03fe63e..ea97c31 100644 > --- a/security/keys/request_key.c > +++ b/security/keys/request_key.c > @@ -68,7 +68,8 @@ static int call_sbin_request_key(struct key_construction *cons, > { > const struct cred *cred = current_cred(); > key_serial_t prkey, sskey; > - struct key *key = cons->key, *authkey = cons->authkey, *keyring; > + struct key *key = cons->key, *authkey = cons->authkey, *keyring, > + *session; > char *argv[9], *envp[3], uid_str[12], gid_str[12]; > char key_str[12], keyring_str[3][12]; > char desc[20]; > @@ -112,10 +113,12 @@ static int call_sbin_request_key(struct key_construction *cons, > if (cred->tgcred->process_keyring) > prkey = cred->tgcred->process_keyring->serial; > > - if (cred->tgcred->session_keyring) > - sskey = rcu_dereference(cred->tgcred->session_keyring)->serial; > - else > - sskey = cred->user->session_keyring->serial; > + rcu_read_lock(); > + session = rcu_dereference(cred->tgcred->session_keyring); > + if (!session) > + session = cred->user->session_keyring; > + sskey = session->serial; > + rcu_read_unlock(); > > sprintf(keyring_str[2], "%d", sskey); > >
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