The patch titled
Check fops_get() return value
has been added to the -mm tree. Its filename is
check-fops_get-return-value.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: Check fops_get() return value
From: Laurent Pinchart <laurent.pinchart@xxxxxxxxx>
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@xxxxxxxxxxxxxx>
Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxx>
Acked-by: Takashi Iwai <tiwai@xxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxx>
Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_fops.c | 4 ++++
drivers/media/dvb/dvb-core/dvbdev.c | 5 +++++
sound/core/sound.c | 4 ++++
3 files changed, 13 insertions(+)
diff -puN drivers/gpu/drm/drm_fops.c~check-fops_get-return-value drivers/gpu/drm/drm_fops.c
--- a/drivers/gpu/drm/drm_fops.c~check-fops_get-return-value
+++ a/drivers/gpu/drm/drm_fops.c
@@ -186,6 +186,10 @@ int drm_stub_open(struct inode *inode, s
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 -puN drivers/media/dvb/dvb-core/dvbdev.c~check-fops_get-return-value drivers/media/dvb/dvb-core/dvbdev.c
--- a/drivers/media/dvb/dvb-core/dvbdev.c~check-fops_get-return-value
+++ a/drivers/media/dvb/dvb-core/dvbdev.c
@@ -85,6 +85,10 @@ static int dvb_device_open(struct inode
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) {
@@ -95,6 +99,7 @@ static int dvb_device_open(struct inode
unlock_kernel();
return err;
}
+fail:
unlock_kernel();
return -ENODEV;
}
diff -puN sound/core/sound.c~check-fops_get-return-value sound/core/sound.c
--- a/sound/core/sound.c~check-fops_get-return-value
+++ a/sound/core/sound.c
@@ -152,6 +152,10 @@ static int __snd_open(struct inode *inod
}
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) {
_
Patches currently in -mm which might be from laurent.pinchart@xxxxxxxxx are
check-fops_get-return-value.patch
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