tty: fix BKL related leak and crash
Enabling the BKL to be lockdep tracked uncovered the following
upstream kernel bug in the tty code, which caused a BKL
reference leak:
================================================
[ BUG: lock held when returning to user space! ]
------------------------------------------------
dmesg/3121 is leaving the kernel with locks still held!
1 lock held by dmesg/3121:
#0: (kernel_mutex){--..}, at: [<c02f34d9>] opost+0x24/0x194
this might explain some of the atomicity warnings and crashes
that -tip tree testing has been experiencing since the BKL
was converted back to a spinlock.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index 19105ec2..8096389 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -282,16 +282,20 @@
if (O_ONLRET(tty))
tty->column = 0;
if (O_ONLCR(tty)) {
- if (space < 2)
+ if (space < 2) {
+ unlock_kernel();
return -1;
+ }
tty_put_char(tty, '\r');
tty->column = 0;
}
tty->canon_column = tty->column;
break;
case '\r':
- if (O_ONOCR(tty) && tty->column == 0)
+ if (O_ONOCR(tty) && tty->column == 0) {
+ unlock_kernel();
return 0;
+ }
if (O_OCRNL(tty)) {
c = '\n';
if (O_ONLRET(tty))
@@ -303,10 +307,13 @@
case '\t':
spaces = 8 - (tty->column & 7);
if (O_TABDLY(tty) == XTABS) {
- if (space < spaces)
+ if (space < spaces) {
+ unlock_kernel();
return -1;
+ }
tty->column += spaces;
tty->ops->write(tty, " ", spaces);
+ unlock_kernel();
return 0;
}
tty->column += spaces;