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authorLaurent Pinchart <laurent.pinchart@skynet.be>2009-01-06 17:40:40 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-06 18:59:11 -0500
commitf41ced8f108cc80f16509b907cd7ac93944459bc (patch)
treee2428887e43f26f373523be3d9ded4427a2c331f
parentbdbeed75b288443ea14208eafaac3941f385f2ae (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.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 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)
183 183
184 old_fops = filp->f_op; 184 old_fops = filp->f_op;
185 filp->f_op = fops_get(&dev->driver->fops); 185 filp->f_op = fops_get(&dev->driver->fops);
186 if (filp->f_op == NULL) {
187 filp->f_op = old_fops;
188 goto out;
189 }
186 if (filp->f_op->open && (err = filp->f_op->open(inode, filp))) { 190 if (filp->f_op->open && (err = filp->f_op->open(inode, filp))) {
187 fops_put(filp->f_op); 191 fops_put(filp->f_op);
188 filp->f_op = fops_get(old_fops); 192 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)
79 file->private_data = dvbdev; 79 file->private_data = dvbdev;
80 old_fops = file->f_op; 80 old_fops = file->f_op;
81 file->f_op = fops_get(dvbdev->fops); 81 file->f_op = fops_get(dvbdev->fops);
82 if (file->f_op == NULL) {
83 file->f_op = old_fops;
84 goto fail;
85 }
82 if(file->f_op->open) 86 if(file->f_op->open)
83 err = file->f_op->open(inode,file); 87 err = file->f_op->open(inode,file);
84 if (err) { 88 if (err) {
@@ -90,6 +94,7 @@ static int dvb_device_open(struct inode *inode, struct file *file)
90 unlock_kernel(); 94 unlock_kernel();
91 return err; 95 return err;
92 } 96 }
97fail:
93 up_read(&minor_rwsem); 98 up_read(&minor_rwsem);
94 unlock_kernel(); 99 unlock_kernel();
95 return -ENODEV; 100 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)
152 } 152 }
153 old_fops = file->f_op; 153 old_fops = file->f_op;
154 file->f_op = fops_get(mptr->f_ops); 154 file->f_op = fops_get(mptr->f_ops);
155 if (file->f_op == NULL) {
156 file->f_op = old_fops;
157 return -ENODEV;
158 }
155 if (file->f_op->open) 159 if (file->f_op->open)
156 err = file->f_op->open(inode, file); 160 err = file->f_op->open(inode, file);
157 if (err) { 161 if (err) {