[PATCH] dquot: add proper locking when using current->signal->tty

Dquot passes the tty to tty_write_message without locking

Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/dquot.c b/fs/dquot.c
index 0122a279106a..9af789567e51 100644
--- a/fs/dquot.c
+++ b/fs/dquot.c
@@ -834,6 +834,9 @@ static void print_warning(struct dquot *dquot, const char warntype)
         if (!need_print_warning(dquot) || (flag && test_and_set_bit(flag, &dquot->dq_flags)))
                 return;
 
+        mutex_lock(&tty_mutex);
+        if (!current->signal->tty)
+                goto out_lock;
         tty_write_message(current->signal->tty, dquot->dq_sb->s_id);
         if (warntype == ISOFTWARN || warntype == BSOFTWARN)
                 tty_write_message(current->signal->tty, ": warning, ");
@@ -861,6 +864,8 @@ static void print_warning(struct dquot *dquot, const char warntype)
                         break;
         }
         tty_write_message(current->signal->tty, msg);
+out_lock:
+        mutex_unlock(&tty_mutex);
 }
 
 static inline void flush_warnings(struct dquot **dquots, char *warntype)