| From | Paul Gortmaker <> | Subject | [34-longterm 141/260] KEYS: Fix RCU no-lock warning in keyctl_session_to_parent() | Date | Sun, 2 Jan 2011 02:17:17 -0500 |
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From: David Howells <dhowells@redhat.com>
commit 9d1ac65a9698513d00e5608d93fca0c53f536c14 upstream.
There's an protected access to the parent process's credentials in the middle of keyctl_session_to_parent(). This results in the following RCU warning:
=================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- security/keys/keyctl.c:1291 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-session-/2137: #0: (tasklist_lock){.+.+..}, at: [<ffffffff811ae2ec>] keyctl_session_to_parent+0x60/0x236
stack backtrace: Pid: 2137, comm: keyctl-session- Not tainted 2.6.36-rc2-cachefs+ #1 Call Trace: [<ffffffff8105606a>] lockdep_rcu_dereference+0xaa/0xb3 [<ffffffff811ae379>] keyctl_session_to_parent+0xed/0x236 [<ffffffff811af77e>] sys_keyctl+0xb4/0xb6 [<ffffffff81001eab>] system_call_fastpath+0x16/0x1b
The code should take the RCU read lock to make sure the parents credentials don't go away, even though it's holding a spinlock and has IRQ disabled.
Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> --- security/keys/keyctl.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index e9c2e7c..d29e022 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -1259,6 +1259,7 @@ long keyctl_session_to_parent(void) keyring_r = NULL; me = current; + rcu_read_lock(); write_lock_irq(&tasklist_lock); parent = me->real_parent; @@ -1313,6 +1314,7 @@ long keyctl_session_to_parent(void) set_ti_thread_flag(task_thread_info(parent), TIF_NOTIFY_RESUME); write_unlock_irq(&tasklist_lock); + rcu_read_unlock(); if (oldcred) put_cred(oldcred); return 0; @@ -1321,6 +1323,7 @@ already_same: ret = 0; not_permitted: write_unlock_irq(&tasklist_lock); + rcu_read_unlock(); put_cred(cred); return ret; -- 1.7.3.3
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