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| author | David Howells <dhowells@redhat.com> | 2010-08-04 16:59:14 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-08-10 11:09:21 -0700 |
| commit | 5232dfac1ac008b5a4df815a5256776913dfa025 (patch) | |
| tree | 26afd8acdd9fe90d48b8ce9bf5cdf4eb43b98337 | |
| parent | 1a0528f57734493e588229266130c247a8e26ac2 (diff) | |
| download | lwn-5232dfac1ac008b5a4df815a5256776913dfa025.tar.gz lwn-5232dfac1ac008b5a4df815a5256776913dfa025.zip | |
CRED: Fix RCU warning due to previous patch fixing __task_cred()'s checks
commit 694f690d27dadccc8cb9d90532e76593b61fe098 upstream.
Commit 8f92054e7ca1 ("CRED: Fix __task_cred()'s lockdep check and banner
comment") fixed the lockdep checks on __task_cred(). This has shown up
a place in the signalling code where a lock should be held - namely that
check_kill_permission() requires its callers to hold the RCU lock.
Fix group_send_sig_info() to get the RCU read lock around its call to
check_kill_permission().
Without this patch, the following warning can occur:
===================================================
[ INFO: suspicious rcu_dereference_check() usage. ]
---------------------------------------------------
kernel/signal.c:660 invoked rcu_dereference_check() without protection!
...
Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | kernel/signal.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/kernel/signal.c b/kernel/signal.c index 906ae5a1779c..bded65187780 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -637,7 +637,7 @@ static inline bool si_fromuser(const struct siginfo *info) /* * Bad permissions for sending the signal - * - the caller must hold at least the RCU read lock + * - the caller must hold the RCU read lock */ static int check_kill_permission(int sig, struct siginfo *info, struct task_struct *t) @@ -1127,11 +1127,14 @@ struct sighand_struct *lock_task_sighand(struct task_struct *tsk, unsigned long /* * send signal info to all the members of a group - * - the caller must hold the RCU read lock at least */ int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p) { - int ret = check_kill_permission(sig, info, p); + int ret; + + rcu_read_lock(); + ret = check_kill_permission(sig, info, p); + rcu_read_unlock(); if (!ret && sig) ret = do_send_sig_info(sig, info, p, true); |