From: Ingo Molnar Date: Wed, 14 May 2008 15:11:46 +0000 (+0200) Subject: tty: fix BKL related leak and crash X-Git-Tag: v2.6.26-rc3~30 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=487ad7efbf6b0ec338cdfc2a7b0fbeb53f17a94c;p=linux-2.6 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: [] 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 Signed-off-by: Linus Torvalds --- diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c index 19105ec203..8096389b0d 100644 --- a/drivers/char/n_tty.c +++ b/drivers/char/n_tty.c @@ -282,16 +282,20 @@ static int opost(unsigned char c, struct tty_struct *tty) 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 @@ static int opost(unsigned char c, struct tty_struct *tty) 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;