Every call to is_orphaned_pgrp passed in process_group(current)
which is racy with respect to another thread changing our process
group. It didn't bite us because we were dealing with integers
and the worse we would get would be a stale answer.
In switching the checks to use struct pid to be a little more
efficient and prepare the way for pid namespaces this
race became apparent.
So I simplified the calls to the more specialized is_current_pgrp_orphaned
so I didn't have to worry about making logic changes to avoid the race.
Signed-off-by: Eric W. Biederman <[email protected]>
---
drivers/char/n_tty.c | 2 +-
drivers/char/tty_io.c | 2 +-
include/linux/tty.h | 2 +-
kernel/exit.c | 4 ++--
kernel/signal.c | 2 +-
5 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index e96a00f..7f1ded8 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -1189,7 +1189,7 @@ static int job_control(struct tty_struct *tty, struct file *file)
printk("read_chan: tty->pgrp <= 0!\n");
else if (process_group(current) != tty->pgrp) {
if (is_ignored(SIGTTIN) ||
- is_orphaned_pgrp(process_group(current)))
+ is_current_pgrp_orphaned())
return -EIO;
kill_pg(process_group(current), SIGTTIN, 1);
return -ERESTARTSYS;
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 74f078a..d8fdf45 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1118,7 +1118,7 @@ int tty_check_change(struct tty_struct * tty)
return 0;
if (is_ignored(SIGTTOU))
return 0;
- if (is_orphaned_pgrp(process_group(current)))
+ if (is_current_pgrp_orphaned())
return -EIO;
(void) kill_pg(process_group(current), SIGTTOU, 1);
return -ERESTARTSYS;
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 1185bca..13a4918 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -283,7 +283,7 @@ extern int tty_read_raw_data(struct tty_struct *tty, unsigned char *bufp,
int buflen);
extern void tty_write_message(struct tty_struct *tty, char *msg);
-extern int is_orphaned_pgrp(int pgrp);
+extern int is_current_pgrp_orphaned(void);
extern int is_ignored(int sig);
extern int tty_signal(int sig, struct tty_struct *tty);
extern void tty_hangup(struct tty_struct * tty);
diff --git a/kernel/exit.c b/kernel/exit.c
index 5f8455e..610917d 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -229,12 +229,12 @@ static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignor
return ret; /* (sighing) "Often!" */
}
-int is_orphaned_pgrp(int pgrp)
+int is_current_pgrp_orphaned(void)
{
int retval;
read_lock(&tasklist_lock);
- retval = will_become_orphaned_pgrp(find_pid(pgrp), NULL);
+ retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
read_unlock(&tasklist_lock);
return retval;
diff --git a/kernel/signal.c b/kernel/signal.c
index 1e34d32..91caafa 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1908,7 +1908,7 @@ relock:
/* signals can be posted during this window */
- if (is_orphaned_pgrp(process_group(current)))
+ if (is_current_pgrp_orphaned())
goto relock;
spin_lock_irq(¤t->sighand->siglock);
--
1.4.4.1.g278f
-
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