From 24ec839c431eb79bb8f6abc00c4e1eb3b8c4d517 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 8 Dec 2006 02:36:04 -0800 Subject: [PATCH] tty: ->signal->tty locking Fix the locking of signal->tty. Use ->sighand->siglock to protect ->signal->tty; this lock is already used by most other members of ->signal/->sighand. And unless we are 'current' or the tasklist_lock is held we need ->siglock to access ->signal anyway. (NOTE: sys_unshare() is broken wrt ->sighand locking rules) Note that tty_mutex is held over tty destruction, so while holding tty_mutex any tty pointer remains valid. Otherwise the lifetime of ttys are governed by their open file handles. This leaves some holes for tty access from signal->tty (or any other non file related tty access). It solves the tty SLAB scribbles we were seeing. (NOTE: the change from group_send_sig_info to __group_send_sig_info needs to be examined by someone familiar with the security framework, I think it is safe given the SEND_SIG_PRIV from other __group_send_sig_info invocations) [schwidefsky@de.ibm.com: 3270 fix] [akpm@osdl.org: various post-viro fixes] Signed-off-by: Peter Zijlstra Acked-by: Alan Cox Cc: Oleg Nesterov Cc: Prarit Bhargava Cc: Chris Wright Cc: Roland McGrath Cc: Stephen Smalley Cc: James Morris Cc: "David S. Miller" Cc: Jeff Dike Cc: Martin Schwidefsky Cc: Jan Kara Signed-off-by: Martin Schwidefsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/acct.c | 9 +++------ kernel/auditsc.c | 2 ++ kernel/exit.c | 4 +--- kernel/sys.c | 6 ++++-- 4 files changed, 10 insertions(+), 11 deletions(-) (limited to 'kernel') diff --git a/kernel/acct.c b/kernel/acct.c index dc12db8..ca56190 100644 --- a/kernel/acct.c +++ b/kernel/acct.c @@ -428,6 +428,7 @@ static void do_acct_process(struct file *file) u64 elapsed; u64 run_time; struct timespec uptime; + struct tty_struct *tty; /* * First check to see if there is enough free_space to continue @@ -485,12 +486,8 @@ static void do_acct_process(struct file *file) #endif mutex_lock(&tty_mutex); - /* FIXME: Whoever is responsible for current->signal locking needs - to use the same locking all over the kernel and document it */ - read_lock(&tasklist_lock); - ac.ac_tty = current->signal->tty ? - old_encode_dev(tty_devnum(current->signal->tty)) : 0; - read_unlock(&tasklist_lock); + tty = get_current_tty(); + ac.ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0; mutex_unlock(&tty_mutex); spin_lock_irq(¤t->sighand->siglock); diff --git a/kernel/auditsc.c b/kernel/auditsc.c index 40722e2..b6cb802 100644 --- a/kernel/auditsc.c +++ b/kernel/auditsc.c @@ -826,10 +826,12 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts context->return_code); mutex_lock(&tty_mutex); + read_lock(&tasklist_lock); if (tsk->signal && tsk->signal->tty && tsk->signal->tty->name) tty = tsk->signal->tty->name; else tty = "(none)"; + read_unlock(&tasklist_lock); audit_log_format(ab, " a0=%lx a1=%lx a2=%lx a3=%lx items=%d" " ppid=%d pid=%d auid=%u uid=%u gid=%u" diff --git a/kernel/exit.c b/kernel/exit.c index 4e3f919..fa23577 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -384,9 +384,7 @@ void daemonize(const char *name, ...) exit_mm(current); set_special_pids(1, 1); - mutex_lock(&tty_mutex); - current->signal->tty = NULL; - mutex_unlock(&tty_mutex); + proc_clear_tty(current); /* Block and flush all signals */ sigfillset(&blocked); diff --git a/kernel/sys.c b/kernel/sys.c index a0c1a29..1ac2d1c5 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1484,7 +1484,6 @@ asmlinkage long sys_setsid(void) pid_t session; int err = -EPERM; - mutex_lock(&tty_mutex); write_lock_irq(&tasklist_lock); /* Fail if I am already a session leader */ @@ -1504,12 +1503,15 @@ asmlinkage long sys_setsid(void) group_leader->signal->leader = 1; __set_special_pids(session, session); + + spin_lock(&group_leader->sighand->siglock); group_leader->signal->tty = NULL; group_leader->signal->tty_old_pgrp = 0; + spin_unlock(&group_leader->sighand->siglock); + err = process_group(group_leader); out: write_unlock_irq(&tasklist_lock); - mutex_unlock(&tty_mutex); return err; } -- cgit v1.1