diff options
| author | Paul Fulghum | 2006-02-14 13:53:00 -0800 |
|---|---|---|
| committer | Linus Torvalds | 2006-02-14 16:09:33 -0800 |
| commit | da965822abd18a17d7cffe1d511f48951c82dfb6 (patch) | |
| tree | b5a64fd33374661dbc689d3192a5c9134b3672e5 /drivers/char | |
| parent | 16bf134840da3920ded1290973c56ec214636f12 (diff) | |
[PATCH] tty reference count fix
Fix hole where tty structure can be released when reference count is non
zero. Existing code can sleep without tty_sem protection between deciding
to release the tty structure (setting local variables tty_closing and
otty_closing) and setting TTY_CLOSING to prevent further opens. An open
can occur during this interval causing release_dev() to free the tty
structure while it is still referenced.
This should fix bugzilla.kernel.org [Bug 6041] New: Unable to handle kernel
paging request
In Bug 6041, tty_open() oopes on accessing the tty structure it has
successfully claimed. Bug was on SMP machine with the same tty being
opened and closed by multiple processes, and DEBUG_PAGEALLOC enabled.
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers/char')
| -rw-r--r-- | drivers/char/tty_io.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c index a23816d3e9a1..e9bba94fc898 100644 --- a/drivers/char/tty_io.c +++ b/drivers/char/tty_io.c @@ -1841,7 +1841,6 @@ static void release_dev(struct file * filp) tty_closing = tty->count <= 1; o_tty_closing = o_tty && (o_tty->count <= (pty_master ? 1 : 0)); - up(&tty_sem); do_sleep = 0; if (tty_closing) { @@ -1869,6 +1868,7 @@ static void release_dev(struct file * filp) printk(KERN_WARNING "release_dev: %s: read/write wait queue " "active!\n", tty_name(tty, buf)); + up(&tty_sem); schedule(); } @@ -1877,8 +1877,6 @@ static void release_dev(struct file * filp) * both sides, and we've completed the last operation that could * block, so it's safe to proceed with closing. */ - - down(&tty_sem); if (pty_master) { if (--o_tty->count < 0) { printk(KERN_WARNING "release_dev: bad pty slave count " @@ -1892,7 +1890,6 @@ static void release_dev(struct file * filp) tty->count, tty_name(tty, buf)); tty->count = 0; } - up(&tty_sem); /* * We've decremented tty->count, so we need to remove this file @@ -1937,6 +1934,8 @@ static void release_dev(struct file * filp) read_unlock(&tasklist_lock); } + up(&tty_sem); + /* check whether both sides are closing ... */ if (!tty_closing || (o_tty && !o_tty_closing)) return; |