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Commit f41ced8f authored by Laurent Pinchart's avatar Laurent Pinchart Committed by Linus Torvalds
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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: default avatarAlan Jenkins <alan-jenkins@tuffmail.co.uk>
Signed-off-by: default avatarLaurent Pinchart <laurent.pinchart@skynet.be>
Acked-by: default avatarTakashi Iwai <tiwai@suse.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Airlie <airlied@linux.ie>
Acked-by: default avatarMauro Carvalho Chehab <mchehab@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bdbeed75

drivers/gpu/drm/drm_fops.c

+4 −0
Original line number Diff line number Diff line
@@ -183,6 +183,10 @@ int drm_stub_open(struct inode *inode, struct file *filp) 


	old_fops = filp->f_op;

	filp->f_op = fops_get(&dev->driver->fops);

	if (filp->f_op == NULL) {

		filp->f_op = old_fops;

		goto out;

	}

	if (filp->f_op->open && (err = filp->f_op->open(inode, filp))) {

		fops_put(filp->f_op);

		filp->f_op = fops_get(old_fops);

drivers/media/dvb/dvb-core/dvbdev.c

+5 −0
Original line number Diff line number Diff line
@@ -79,6 +79,10 @@ static int dvb_device_open(struct inode *inode, struct file *file) 
		file->private_data = dvbdev;

		old_fops = file->f_op;

		file->f_op = fops_get(dvbdev->fops);

		if (file->f_op == NULL) {

			file->f_op = old_fops;

			goto fail;

		}

		if(file->f_op->open)

			err = file->f_op->open(inode,file);

		if (err) {
@@ -90,6 +94,7 @@ static int dvb_device_open(struct inode *inode, struct file *file) 
		unlock_kernel();

		return err;

	}

fail:

	up_read(&minor_rwsem);

	unlock_kernel();

	return -ENODEV;

sound/core/sound.c

+4 −0
Original line number Diff line number Diff line
@@ -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) {