diff options
| author | Laurent Pinchart <laurent.pinchart@skynet.be> | 2009-01-06 14:40:40 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-01-06 15:59:11 -0800 |
| commit | f41ced8f108cc80f16509b907cd7ac93944459bc (patch) | |
| tree | e2428887e43f26f373523be3d9ded4427a2c331f | |
| parent | bdbeed75b288443ea14208eafaac3941f385f2ae (diff) | |
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 <alan-jenkins@tuffmail.co.uk>
Signed-off-by: Laurent Pinchart <laurent.pinchart@skynet.be>
Acked-by: Takashi Iwai <tiwai@suse.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Airlie <airlied@linux.ie>
Acked-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | drivers/gpu/drm/drm_fops.c | 4 | ||||
| -rw-r--r-- | drivers/media/dvb/dvb-core/dvbdev.c | 5 | ||||
| -rw-r--r-- | sound/core/sound.c | 4 |
3 files changed, 13 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c index 3733e36d135e..b06a53715853 100644 --- a/drivers/gpu/drm/drm_fops.c +++ b/drivers/gpu/drm/drm_fops.c @@ -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); diff --git a/drivers/media/dvb/dvb-core/dvbdev.c b/drivers/media/dvb/dvb-core/dvbdev.c index 65d69665f1fc..6a32680dbb1b 100644 --- a/drivers/media/dvb/dvb-core/dvbdev.c +++ b/drivers/media/dvb/dvb-core/dvbdev.c @@ -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; 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) { |