diff mbox

[2/4] carl9170: fix debugfs crashes

Message ID ccf228acb7af8ee3bbd82f72f28ebc068f37cb8e.1474140477.git.chunkeey@gmail.com (mailing list archive)
State Not Applicable
Delegated to: Kalle Valo
Headers show

Commit Message

Christian Lamparter Sept. 17, 2016, 7:43 p.m. UTC
Ben Greear reported:
> I see lots of instability as soon as I load up the carl9710 NIC.
> My application is going to be poking at it's debugfs files...
>
> BUG: KASAN: slab-out-of-bounds in carl9170_debugfs_read+0xd5/0x2a0
> [carl9170] at addr ffff8801bc1208b0
> Read of size 8 by task btserver/5888
> =======================================================================
> BUG kmalloc-256 (Tainted: G        W      ): kasan: bad access detected
> -----------------------------------------------------------------------
>
> INFO: Allocated in seq_open+0x50/0x100 age=2690 cpu=2 pid=772
>...

This breakage was caused by the introduction of intermediate
fops in debugfs by commit 9fd4dcece43a
("debugfs: prevent access to possibly dead file_operations at file open")

Thankfully, the original/real fops are still available in d_fsdata.

Reported-by: Ben Greear <greearb@candelatech.com>
Reviewed-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
---
 drivers/net/wireless/ath/carl9170/debug.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Greg Kroah-Hartman Sept. 17, 2016, 9:45 p.m. UTC | #1
On Sat, Sep 17, 2016 at 09:43:02PM +0200, Christian Lamparter wrote:
> Ben Greear reported:
> > I see lots of instability as soon as I load up the carl9710 NIC.
> > My application is going to be poking at it's debugfs files...
> >
> > BUG: KASAN: slab-out-of-bounds in carl9170_debugfs_read+0xd5/0x2a0
> > [carl9170] at addr ffff8801bc1208b0
> > Read of size 8 by task btserver/5888
> > =======================================================================
> > BUG kmalloc-256 (Tainted: G        W      ): kasan: bad access detected
> > -----------------------------------------------------------------------
> >
> > INFO: Allocated in seq_open+0x50/0x100 age=2690 cpu=2 pid=772
> >...
> 
> This breakage was caused by the introduction of intermediate
> fops in debugfs by commit 9fd4dcece43a
> ("debugfs: prevent access to possibly dead file_operations at file open")

Because of this, these should all be backported to 4.7-stable, and
4.8-stable, right?

thanks,

greg k-h
Kalle Valo Sept. 18, 2016, 7:54 a.m. UTC | #2
Greg KH <gregkh@linuxfoundation.org> writes:

> On Sat, Sep 17, 2016 at 09:43:02PM +0200, Christian Lamparter wrote:
>> Ben Greear reported:
>> > I see lots of instability as soon as I load up the carl9710 NIC.
>> > My application is going to be poking at it's debugfs files...
>> >
>> > BUG: KASAN: slab-out-of-bounds in carl9170_debugfs_read+0xd5/0x2a0
>> > [carl9170] at addr ffff8801bc1208b0
>> > Read of size 8 by task btserver/5888
>> > =======================================================================
>> > BUG kmalloc-256 (Tainted: G        W      ): kasan: bad access detected
>> > -----------------------------------------------------------------------
>> >
>> > INFO: Allocated in seq_open+0x50/0x100 age=2690 cpu=2 pid=772
>> >...
>> 
>> This breakage was caused by the introduction of intermediate
>> fops in debugfs by commit 9fd4dcece43a
>> ("debugfs: prevent access to possibly dead file_operations at file open")
>
> Because of this, these should all be backported to 4.7-stable, and
> 4.8-stable, right?

Via which tree should these go, Greg's or mine?
Greg Kroah-Hartman Sept. 18, 2016, 10:14 a.m. UTC | #3
On Sun, Sep 18, 2016 at 10:54:18AM +0300, Kalle Valo wrote:
> Greg KH <gregkh@linuxfoundation.org> writes:
> 
> > On Sat, Sep 17, 2016 at 09:43:02PM +0200, Christian Lamparter wrote:
> >> Ben Greear reported:
> >> > I see lots of instability as soon as I load up the carl9710 NIC.
> >> > My application is going to be poking at it's debugfs files...
> >> >
> >> > BUG: KASAN: slab-out-of-bounds in carl9170_debugfs_read+0xd5/0x2a0
> >> > [carl9170] at addr ffff8801bc1208b0
> >> > Read of size 8 by task btserver/5888
> >> > =======================================================================
> >> > BUG kmalloc-256 (Tainted: G        W      ): kasan: bad access detected
> >> > -----------------------------------------------------------------------
> >> >
> >> > INFO: Allocated in seq_open+0x50/0x100 age=2690 cpu=2 pid=772
> >> >...
> >> 
> >> This breakage was caused by the introduction of intermediate
> >> fops in debugfs by commit 9fd4dcece43a
> >> ("debugfs: prevent access to possibly dead file_operations at file open")
> >
> > Because of this, these should all be backported to 4.7-stable, and
> > 4.8-stable, right?
> 
> Via which tree should these go, Greg's or mine?

I'll take it if you ack it, as it's a debugfs issue.

thanks,

greg k-h
Christian Lamparter Sept. 18, 2016, 12:49 p.m. UTC | #4
On Sunday, September 18, 2016 12:14:55 PM CEST Greg KH wrote:
> On Sun, Sep 18, 2016 at 10:54:18AM +0300, Kalle Valo wrote:
> > Greg KH <gregkh@linuxfoundation.org> writes:
> > 
> > > On Sat, Sep 17, 2016 at 09:43:02PM +0200, Christian Lamparter wrote:
> > >> Ben Greear reported:
> > >> > I see lots of instability as soon as I load up the carl9710 NIC.
> > >> > My application is going to be poking at it's debugfs files...
> > >> >
> > >> > BUG: KASAN: slab-out-of-bounds in carl9170_debugfs_read+0xd5/0x2a0
> > >> > [carl9170] at addr ffff8801bc1208b0
> > >> > Read of size 8 by task btserver/5888
> > >> > =======================================================================
> > >> > BUG kmalloc-256 (Tainted: G        W      ): kasan: bad access detected
> > >> > -----------------------------------------------------------------------
> > >> >
> > >> > INFO: Allocated in seq_open+0x50/0x100 age=2690 cpu=2 pid=772
> > >> >...
> > >> 
> > >> This breakage was caused by the introduction of intermediate
> > >> fops in debugfs by commit 9fd4dcece43a
> > >> ("debugfs: prevent access to possibly dead file_operations at file open")
> > >
> > > Because of this, these should all be backported to 4.7-stable, and
> > > 4.8-stable, right?
Ok, only b43legacy has debugfs enabled by default. For b43 and carl9170 
debugfs support is usually disabled.

Greg, would you take these four patches "as is" for -stable
or do you want a "minimal version" which just replaces the

dfops = container_of(file->f_op, ...

with

dfops = container_of(file->f_path.dentry->d_fsdata, ...

in the three drivers for -stable?

> > Via which tree should these go, Greg's or mine?
> 
> I'll take it if you ack it, as it's a debugfs issue.
For carl9170: Ben Greear has reported:
"I have verified this fixes my problem in the 4.7 kernel."

But this was with a preliminary/minimal version so I didn't
add the tested-by tag.

As for b43, I'll see if I have a working b43 in my collection
somewhere to confirm the issue and the fix. Question is, do
you want to wait or not?

Regards,
Christian
Greg Kroah-Hartman Sept. 18, 2016, 4:44 p.m. UTC | #5
On Sun, Sep 18, 2016 at 02:49:33PM +0200, Christian Lamparter wrote:
> On Sunday, September 18, 2016 12:14:55 PM CEST Greg KH wrote:
> > On Sun, Sep 18, 2016 at 10:54:18AM +0300, Kalle Valo wrote:
> > > Greg KH <gregkh@linuxfoundation.org> writes:
> > > 
> > > > On Sat, Sep 17, 2016 at 09:43:02PM +0200, Christian Lamparter wrote:
> > > >> Ben Greear reported:
> > > >> > I see lots of instability as soon as I load up the carl9710 NIC.
> > > >> > My application is going to be poking at it's debugfs files...
> > > >> >
> > > >> > BUG: KASAN: slab-out-of-bounds in carl9170_debugfs_read+0xd5/0x2a0
> > > >> > [carl9170] at addr ffff8801bc1208b0
> > > >> > Read of size 8 by task btserver/5888
> > > >> > =======================================================================
> > > >> > BUG kmalloc-256 (Tainted: G        W      ): kasan: bad access detected
> > > >> > -----------------------------------------------------------------------
> > > >> >
> > > >> > INFO: Allocated in seq_open+0x50/0x100 age=2690 cpu=2 pid=772
> > > >> >...
> > > >> 
> > > >> This breakage was caused by the introduction of intermediate
> > > >> fops in debugfs by commit 9fd4dcece43a
> > > >> ("debugfs: prevent access to possibly dead file_operations at file open")
> > > >
> > > > Because of this, these should all be backported to 4.7-stable, and
> > > > 4.8-stable, right?
> Ok, only b43legacy has debugfs enabled by default. For b43 and carl9170 
> debugfs support is usually disabled.
> 
> Greg, would you take these four patches "as is" for -stable
> or do you want a "minimal version" which just replaces the
> 
> dfops = container_of(file->f_op, ...
> 
> with
> 
> dfops = container_of(file->f_path.dentry->d_fsdata, ...
> 
> in the three drivers for -stable?

No, I'll take this as is, we want things to remain as close as possible
to Linus's tree.  When we are not, is when things break.

> > > Via which tree should these go, Greg's or mine?
> > 
> > I'll take it if you ack it, as it's a debugfs issue.
> For carl9170: Ben Greear has reported:
> "I have verified this fixes my problem in the 4.7 kernel."
> 
> But this was with a preliminary/minimal version so I didn't
> add the tested-by tag.
> 
> As for b43, I'll see if I have a working b43 in my collection
> somewhere to confirm the issue and the fix. Question is, do
> you want to wait or not?

I'll queue these up this week, no rush.

thanks,

greg k-h
Kalle Valo Sept. 18, 2016, 4:57 p.m. UTC | #6
Greg KH <gregkh@linuxfoundation.org> writes:

> On Sun, Sep 18, 2016 at 10:54:18AM +0300, Kalle Valo wrote:
>> Greg KH <gregkh@linuxfoundation.org> writes:
>> 
>> > On Sat, Sep 17, 2016 at 09:43:02PM +0200, Christian Lamparter wrote:
>> >> Ben Greear reported:
>> >> > I see lots of instability as soon as I load up the carl9710 NIC.
>> >> > My application is going to be poking at it's debugfs files...
>> >> >
>> >> > BUG: KASAN: slab-out-of-bounds in carl9170_debugfs_read+0xd5/0x2a0
>> >> > [carl9170] at addr ffff8801bc1208b0
>> >> > Read of size 8 by task btserver/5888
>> >> > =======================================================================
>> >> > BUG kmalloc-256 (Tainted: G        W      ): kasan: bad access detected
>> >> > -----------------------------------------------------------------------
>> >> >
>> >> > INFO: Allocated in seq_open+0x50/0x100 age=2690 cpu=2 pid=772
>> >> >...
>> >> 
>> >> This breakage was caused by the introduction of intermediate
>> >> fops in debugfs by commit 9fd4dcece43a
>> >> ("debugfs: prevent access to possibly dead file_operations at file open")
>> >
>> > Because of this, these should all be backported to 4.7-stable, and
>> > 4.8-stable, right?
>> 
>> Via which tree should these go, Greg's or mine?
>
> I'll take it if you ack it, as it's a debugfs issue.

Good, thanks. The wireless patches look good to me so:

Acked-by: Kalle Valo <kvalo@codeaurora.org>
Christian Lamparter Sept. 19, 2016, 8:12 p.m. UTC | #7
On Sunday, September 18, 2016 6:44:08 PM CEST Greg KH wrote:
> On Sun, Sep 18, 2016 at 02:49:33PM +0200, Christian Lamparter wrote:
> > On Sunday, September 18, 2016 12:14:55 PM CEST Greg KH wrote:
> > > On Sun, Sep 18, 2016 at 10:54:18AM +0300, Kalle Valo wrote:
> > > > Greg KH <gregkh@linuxfoundation.org> writes:
> > > > 
> > > > > On Sat, Sep 17, 2016 at 09:43:02PM +0200, Christian Lamparter wrote:
> > > > >> Ben Greear reported:
> > > > >> > I see lots of instability as soon as I load up the carl9710 NIC.
> > > > >> > My application is going to be poking at it's debugfs files...
> > > > >> >
> > > > >> > BUG: KASAN: slab-out-of-bounds in carl9170_debugfs_read+0xd5/0x2a0
> > > > >> > [carl9170] at addr ffff8801bc1208b0
> > > > >> > Read of size 8 by task btserver/5888
> > > > >> > =======================================================================
> > > > >> > BUG kmalloc-256 (Tainted: G        W      ): kasan: bad access detected
> > > > >> > -----------------------------------------------------------------------
> > > > >> >
> > > > >> > INFO: Allocated in seq_open+0x50/0x100 age=2690 cpu=2 pid=772
> > > > >> >...
> > > > >> 
> > > > >> This breakage was caused by the introduction of intermediate
> > > > >> fops in debugfs by commit 9fd4dcece43a
> > > > >> ("debugfs: prevent access to possibly dead file_operations at file open")
> > > > >
> > > > > Because of this, these should all be backported to 4.7-stable, and
> > > > > 4.8-stable, right?
> > Ok, only b43legacy has debugfs enabled by default. For b43 and carl9170 
> > debugfs support is usually disabled.
> > 
> > Greg, would you take these four patches "as is" for -stable
> > or do you want a "minimal version" which just replaces the
> > 
> > dfops = container_of(file->f_op, ...
> > 
> > with
> > 
> > dfops = container_of(file->f_path.dentry->d_fsdata, ...
> > 
> > in the three drivers for -stable?
> 
> No, I'll take this as is, we want things to remain as close as possible
> to Linus's tree.  When we are not, is when things break.
> 
> > > > Via which tree should these go, Greg's or mine?
> > > 
> > > I'll take it if you ack it, as it's a debugfs issue.
> > For carl9170: Ben Greear has reported:
> > "I have verified this fixes my problem in the 4.7 kernel."
> > 
> > But this was with a preliminary/minimal version so I didn't
> > add the tested-by tag.
> > 
> > As for b43, I'll see if I have a working b43 in my collection
> > somewhere to confirm the issue and the fix. Question is, do
> > you want to wait or not?
> 
> I'll queue these up this week, no rush.

I was able to sucessfully test the b43 patch on my iBook G4's BCM4306.

Thanks,

Christian
Greg Kroah-Hartman Sept. 20, 2016, 6:50 a.m. UTC | #8
On Mon, Sep 19, 2016 at 10:12:08PM +0200, Christian Lamparter wrote:
> On Sunday, September 18, 2016 6:44:08 PM CEST Greg KH wrote:
> > On Sun, Sep 18, 2016 at 02:49:33PM +0200, Christian Lamparter wrote:
> > > On Sunday, September 18, 2016 12:14:55 PM CEST Greg KH wrote:
> > > > On Sun, Sep 18, 2016 at 10:54:18AM +0300, Kalle Valo wrote:
> > > > > Greg KH <gregkh@linuxfoundation.org> writes:
> > > > > 
> > > > > > On Sat, Sep 17, 2016 at 09:43:02PM +0200, Christian Lamparter wrote:
> > > > > >> Ben Greear reported:
> > > > > >> > I see lots of instability as soon as I load up the carl9710 NIC.
> > > > > >> > My application is going to be poking at it's debugfs files...
> > > > > >> >
> > > > > >> > BUG: KASAN: slab-out-of-bounds in carl9170_debugfs_read+0xd5/0x2a0
> > > > > >> > [carl9170] at addr ffff8801bc1208b0
> > > > > >> > Read of size 8 by task btserver/5888
> > > > > >> > =======================================================================
> > > > > >> > BUG kmalloc-256 (Tainted: G        W      ): kasan: bad access detected
> > > > > >> > -----------------------------------------------------------------------
> > > > > >> >
> > > > > >> > INFO: Allocated in seq_open+0x50/0x100 age=2690 cpu=2 pid=772
> > > > > >> >...
> > > > > >> 
> > > > > >> This breakage was caused by the introduction of intermediate
> > > > > >> fops in debugfs by commit 9fd4dcece43a
> > > > > >> ("debugfs: prevent access to possibly dead file_operations at file open")
> > > > > >
> > > > > > Because of this, these should all be backported to 4.7-stable, and
> > > > > > 4.8-stable, right?
> > > Ok, only b43legacy has debugfs enabled by default. For b43 and carl9170 
> > > debugfs support is usually disabled.
> > > 
> > > Greg, would you take these four patches "as is" for -stable
> > > or do you want a "minimal version" which just replaces the
> > > 
> > > dfops = container_of(file->f_op, ...
> > > 
> > > with
> > > 
> > > dfops = container_of(file->f_path.dentry->d_fsdata, ...
> > > 
> > > in the three drivers for -stable?
> > 
> > No, I'll take this as is, we want things to remain as close as possible
> > to Linus's tree.  When we are not, is when things break.
> > 
> > > > > Via which tree should these go, Greg's or mine?
> > > > 
> > > > I'll take it if you ack it, as it's a debugfs issue.
> > > For carl9170: Ben Greear has reported:
> > > "I have verified this fixes my problem in the 4.7 kernel."
> > > 
> > > But this was with a preliminary/minimal version so I didn't
> > > add the tested-by tag.
> > > 
> > > As for b43, I'll see if I have a working b43 in my collection
> > > somewhere to confirm the issue and the fix. Question is, do
> > > you want to wait or not?
> > 
> > I'll queue these up this week, no rush.
> 
> I was able to sucessfully test the b43 patch on my iBook G4's BCM4306.

So is that a "Tested-by:"?  :)
Greg Kroah-Hartman Sept. 21, 2016, 10:13 a.m. UTC | #9
On Sat, Sep 17, 2016 at 09:43:02PM +0200, Christian Lamparter wrote:
> Ben Greear reported:
> > I see lots of instability as soon as I load up the carl9710 NIC.
> > My application is going to be poking at it's debugfs files...
> >
> > BUG: KASAN: slab-out-of-bounds in carl9170_debugfs_read+0xd5/0x2a0
> > [carl9170] at addr ffff8801bc1208b0
> > Read of size 8 by task btserver/5888
> > =======================================================================
> > BUG kmalloc-256 (Tainted: G        W      ): kasan: bad access detected
> > -----------------------------------------------------------------------
> >
> > INFO: Allocated in seq_open+0x50/0x100 age=2690 cpu=2 pid=772
> >...
> 
> This breakage was caused by the introduction of intermediate
> fops in debugfs by commit 9fd4dcece43a
> ("debugfs: prevent access to possibly dead file_operations at file open")
> 
> Thankfully, the original/real fops are still available in d_fsdata.
> 
> Reported-by: Ben Greear <greearb@candelatech.com>
> Reviewed-by: Nicolai Stange <nicstange@gmail.com>
> Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
> Acked-by: Kalle Valo <kvalo@codeaurora.org>
> Cc: stable <stable@vger.kernel.org> # 4.7+
> ---
>  drivers/net/wireless/ath/carl9170/debug.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/carl9170/debug.c b/drivers/net/wireless/ath/carl9170/debug.c
> index 01a0919..ad7ffd5 100644
> --- a/drivers/net/wireless/ath/carl9170/debug.c
> +++ b/drivers/net/wireless/ath/carl9170/debug.c
> @@ -75,7 +75,7 @@ static ssize_t carl9170_debugfs_read(struct file *file, char __user *userbuf,
>  
>  	if (!ar)
>  		return -ENODEV;
> -	dfops = container_of(file->f_path.dentry->d_fsdata,
> +	dfops = container_of(debugfs_real_fops(file),
>  			     struct carl9170_debugfs_fops, fops);
>  
>  	if (!dfops->read)
> @@ -128,7 +128,7 @@ static ssize_t carl9170_debugfs_write(struct file *file,
>  
>  	if (!ar)
>  		return -ENODEV;
> -	dfops = container_of(file->f_path.dentry->d_fsdata,
> +	dfops = container_of(debugfs_real_fops(file),
>  			     struct carl9170_debugfs_fops, fops);
>  	if (!dfops->write)
>  		return -ENOSYS;

What tree is this against?  I can't apply it to 4.8-rc5, or 4.8-rc7, are
you sure it is still needed?

thanks,

greg k-h
Christian Lamparter Sept. 21, 2016, 4:29 p.m. UTC | #10
On Wednesday, September 21, 2016 12:13:25 PM CEST Greg KH wrote:
> On Sat, Sep 17, 2016 at 09:43:02PM +0200, Christian Lamparter wrote:
> > Ben Greear reported:
> > > I see lots of instability as soon as I load up the carl9710 NIC.
> > > My application is going to be poking at it's debugfs files...
> > >
> > > BUG: KASAN: slab-out-of-bounds in carl9170_debugfs_read+0xd5/0x2a0
> > > [carl9170] at addr ffff8801bc1208b0
> > > Read of size 8 by task btserver/5888
> > > =======================================================================
> > > BUG kmalloc-256 (Tainted: G        W      ): kasan: bad access detected
> > > -----------------------------------------------------------------------
> > >
> > > INFO: Allocated in seq_open+0x50/0x100 age=2690 cpu=2 pid=772
> > >...
> > 
> > This breakage was caused by the introduction of intermediate
> > fops in debugfs by commit 9fd4dcece43a
> > ("debugfs: prevent access to possibly dead file_operations at file open")
> > 
> > Thankfully, the original/real fops are still available in d_fsdata.
> > 
> > Reported-by: Ben Greear <greearb@candelatech.com>
> > Reviewed-by: Nicolai Stange <nicstange@gmail.com>
> > Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
> > Acked-by: Kalle Valo <kvalo@codeaurora.org>
> > Cc: stable <stable@vger.kernel.org> # 4.7+
> > ---
> >  drivers/net/wireless/ath/carl9170/debug.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/wireless/ath/carl9170/debug.c b/drivers/net/wireless/ath/carl9170/debug.c
> > index 01a0919..ad7ffd5 100644
> > --- a/drivers/net/wireless/ath/carl9170/debug.c
> > +++ b/drivers/net/wireless/ath/carl9170/debug.c
> > @@ -75,7 +75,7 @@ static ssize_t carl9170_debugfs_read(struct file *file, char __user *userbuf,
> >  
> >  	if (!ar)
> >  		return -ENODEV;
> > -	dfops = container_of(file->f_path.dentry->d_fsdata,
> > +	dfops = container_of(debugfs_real_fops(file),
> >  			     struct carl9170_debugfs_fops, fops);
> >  
> >  	if (!dfops->read)
> > @@ -128,7 +128,7 @@ static ssize_t carl9170_debugfs_write(struct file *file,
> >  
> >  	if (!ar)
> >  		return -ENODEV;
> > -	dfops = container_of(file->f_path.dentry->d_fsdata,
> > +	dfops = container_of(debugfs_real_fops(file),
> >  			     struct carl9170_debugfs_fops, fops);
> >  	if (!dfops->write)
> >  		return -ENOSYS;
> 
> What tree is this against?  I can't apply it to 4.8-rc5, or 4.8-rc7, are
> you sure it is still needed?
---
Yes, the patch is needed. That said I screwed this patch up and as a result
it is faulty. I'll send out v2 shortly

Thanks,
Christian
diff mbox

Patch

diff --git a/drivers/net/wireless/ath/carl9170/debug.c b/drivers/net/wireless/ath/carl9170/debug.c
index 01a0919..ad7ffd5 100644
--- a/drivers/net/wireless/ath/carl9170/debug.c
+++ b/drivers/net/wireless/ath/carl9170/debug.c
@@ -75,7 +75,7 @@  static ssize_t carl9170_debugfs_read(struct file *file, char __user *userbuf,
 
 	if (!ar)
 		return -ENODEV;
-	dfops = container_of(file->f_path.dentry->d_fsdata,
+	dfops = container_of(debugfs_real_fops(file),
 			     struct carl9170_debugfs_fops, fops);
 
 	if (!dfops->read)
@@ -128,7 +128,7 @@  static ssize_t carl9170_debugfs_write(struct file *file,
 
 	if (!ar)
 		return -ENODEV;
-	dfops = container_of(file->f_path.dentry->d_fsdata,
+	dfops = container_of(debugfs_real_fops(file),
 			     struct carl9170_debugfs_fops, fops);
 	if (!dfops->write)
 		return -ENOSYS;