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authorLaurent Pinchart <laurent.pinchart@skynet.be>2009-01-06 14:40:40 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-06 15:59:11 -0800
commitf41ced8f108cc80f16509b907cd7ac93944459bc (patch)
treee2428887e43f26f373523be3d9ded4427a2c331f
parentbdbeed75b288443ea14208eafaac3941f385f2ae (diff)
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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: 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.c4
-rw-r--r--drivers/media/dvb/dvb-core/dvbdev.c5
-rw-r--r--sound/core/sound.c4
3 files changed, 13 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
index 3733e36d135..b06a5371585 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 65d69665f1f..6a32680dbb1 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 44a69bb8d4f..7872a02f6ca 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) {