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authorLinus Torvalds <torvalds@linux-foundation.org>2009-08-03 14:54:56 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2009-08-04 13:46:30 -0700
commitcbe9352fa08f90aa03b4dbf1bbabfc95d196e562 (patch)
tree960187b610e13e5ef7f461397bd0846a36221436
parent65b770468e98941e45e19780dff9283e663e6b8b (diff)
tty-ldisc: be more careful in 'put_ldisc' locking
Use 'atomic_dec_and_lock()' to make sure that we always hold the tty_ldisc_lock when the ldisc count goes to zero. That way we can never race against 'tty_ldisc_try()' increasing the count again. Reported-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Tested-by: Sergey Senozhatsky <sergey.senozhatsky@mail.by> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/char/tty_ldisc.c17
1 files changed, 12 insertions, 5 deletions
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index be55dfcf59a..1733d3439ad 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -55,25 +55,32 @@ static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld)
return ld;
}
-static inline void put_ldisc(struct tty_ldisc *ld)
+static void put_ldisc(struct tty_ldisc *ld)
{
+ unsigned long flags;
+
if (WARN_ON_ONCE(!ld))
return;
/*
* If this is the last user, free the ldisc, and
* release the ldisc ops.
+ *
+ * We really want an "atomic_dec_and_lock_irqsave()",
+ * but we don't have it, so this does it by hand.
*/
- if (atomic_dec_and_test(&ld->users)) {
- unsigned long flags;
+ local_irq_save(flags);
+ if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) {
struct tty_ldisc_ops *ldo = ld->ops;
- kfree(ld);
- spin_lock_irqsave(&tty_ldisc_lock, flags);
ldo->refcount--;
module_put(ldo->owner);
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+
+ kfree(ld);
+ return;
}
+ local_irq_restore(flags);
}
/**