From f41ced8f108cc80f16509b907cd7ac93944459bc Mon Sep 17 00:00:00 2001 From: Laurent Pinchart Date: Tue, 6 Jan 2009 14:40:40 -0800 Subject: Check fops_get() return value Several subsystem open handlers dereference the fops_get() return value without checking it for nullness. This opens a race condition between the open handler and module unloading. A module can be marked as being unloaded (MODULE_STATE_GOING) before its exit function is called and gets the chance to unregister the driver. During that window open handlers can still be called, and fops_get() will fail in try_module_get() and return a NULL pointer. This change checks the fops_get() return value and returns -ENODEV if NULL. Reported-by: Alan Jenkins Signed-off-by: Laurent Pinchart Acked-by: Takashi Iwai Cc: Al Viro Cc: Dave Airlie Acked-by: Mauro Carvalho Chehab Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- sound/core/sound.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'sound') diff --git a/sound/core/sound.c b/sound/core/sound.c index 44a69bb8d4f0..7872a02f6ca9 100644 --- a/sound/core/sound.c +++ b/sound/core/sound.c @@ -152,6 +152,10 @@ static int __snd_open(struct inode *inode, struct file *file) } old_fops = file->f_op; file->f_op = fops_get(mptr->f_ops); + if (file->f_op == NULL) { + file->f_op = old_fops; + return -ENODEV; + } if (file->f_op->open) err = file->f_op->open(inode, file); if (err) { -- cgit v1.2.3-59-g8ed1b