From 3b5e9e53c6f31b5a5a0f5c43707503c62bdefa46 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 30 Apr 2008 00:52:42 -0700 Subject: [PATCH] signals: cleanup security_task_kill() usage/implementation Every implementation of ->task_kill() does nothing when the signal comes from the kernel. This is correct, but means that check_kill_permission() should call security_task_kill() only for SI_FROMUSER() case, and we can remove the same check from ->task_kill() implementations. (sadly, check_kill_permission() is the last user of signal->session/__session but we can't s/task_session_nr/task_session/ here). NOTE: Eric W. Biederman pointed out cap_task_kill() should die, and I think he is very right. Signed-off-by: Oleg Nesterov Cc: "Eric W. Biederman" Cc: Serge Hallyn Cc: Roland McGrath Cc: Casey Schaufler Cc: David Quigley Cc: Eric Paris Cc: Harald Welte Cc: Pavel Emelyanov Cc: Stephen Smalley Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 27 ++++++++++++++------------- security/selinux/hooks.c | 3 --- security/smack/smack_lsm.c | 9 --------- 3 files changed, 14 insertions(+), 25 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index f9a52c721274..91d57f89f5a5 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -533,22 +533,23 @@ static int rm_from_queue(unsigned long mask, struct sigpending *s) static int check_kill_permission(int sig, struct siginfo *info, struct task_struct *t) { - int error = -EINVAL; + int error; + if (!valid_signal(sig)) - return error; + return -EINVAL; - if (info == SEND_SIG_NOINFO || (!is_si_special(info) && SI_FROMUSER(info))) { - error = audit_signal_info(sig, t); /* Let audit system see the signal */ - if (error) - return error; - error = -EPERM; - if (((sig != SIGCONT) || - (task_session_nr(current) != task_session_nr(t))) - && (current->euid ^ t->suid) && (current->euid ^ t->uid) - && (current->uid ^ t->suid) && (current->uid ^ t->uid) - && !capable(CAP_KILL)) + if (info != SEND_SIG_NOINFO && (is_si_special(info) || SI_FROMKERNEL(info))) + return 0; + + error = audit_signal_info(sig, t); /* Let audit system see the signal */ + if (error) return error; - } + + if (((sig != SIGCONT) || (task_session_nr(current) != task_session_nr(t))) + && (current->euid ^ t->suid) && (current->euid ^ t->uid) + && (current->uid ^ t->suid) && (current->uid ^ t->uid) + && !capable(CAP_KILL)) + return -EPERM; return security_task_kill(t, info, sig, 0); } diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 85a220465a8f..1b50a6ebc55f 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3286,9 +3286,6 @@ static int selinux_task_kill(struct task_struct *p, struct siginfo *info, if (rc) return rc; - if (info != SEND_SIG_NOINFO && (is_si_special(info) || SI_FROMKERNEL(info))) - return 0; - if (!sig) perm = PROCESS__SIGNULL; /* null signal; existence test */ else diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index fe0ae1bf1650..b5c8f9237008 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -1130,15 +1130,6 @@ static int smack_task_movememory(struct task_struct *p) static int smack_task_kill(struct task_struct *p, struct siginfo *info, int sig, u32 secid) { - /* - * Special cases where signals really ought to go through - * in spite of policy. Stephen Smalley suggests it may - * make sense to change the caller so that it doesn't - * bother with the LSM hook in these cases. - */ - if (info != SEND_SIG_NOINFO && - (is_si_special(info) || SI_FROMKERNEL(info))) - return 0; /* * Sending a signal requires that the sender * can write the receiver. -- 2.30.2