From: David Howells Date: Wed, 4 Aug 2010 15:59:14 +0000 (+0100) Subject: CRED: Fix RCU warning due to previous patch fixing __task_cred()'s checks X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=694f690d27dadccc8cb9d90532e76593b61fe098;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git CRED: Fix RCU warning due to previous patch fixing __task_cred()'s checks 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 Signed-off-by: David Howells Acked-by: Oleg Nesterov Signed-off-by: Linus Torvalds --- 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);