[PATCH] seq_file: fix passing wrong private data

linux-fsdevel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed

* [PATCH] seq_file: fix passing wrong private data
@ 2021-10-29  3:26 Muchun Song
  2021-10-29  8:26 ` Christian Brauner
  0 siblings, 1 reply; 5+ messages in thread
From: Muchun Song @ 2021-10-29  3:26 UTC (permalink / raw)
  To: andriy.shevchenko, akpm, sfr, revest, adobriyan
  Cc: linux-kernel, linux-fsdevel, Muchun Song

DEFINE_PROC_SHOW_ATTRIBUTE() is supposed to be used to define a series
of functions and variables to register proc file easily. And the users
can use proc_create_data() to pass their own private data and get it
via seq->private in the callback. Unfortunately, the proc file system
use PDE_DATA() to get private data instead of inode->i_private. So fix
it. Fortunately, there only one user of it which does not pass any
private data, so this bug does not break any in-tree codes.

Fixes: 97a32539b956 ("proc: convert everything to "struct proc_ops"")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 include/linux/seq_file.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 103776e18555..72dbb44a4573 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -209,7 +209,7 @@ static const struct file_operations __name ## _fops = {			\
 #define DEFINE_PROC_SHOW_ATTRIBUTE(__name)				\
 static int __name ## _open(struct inode *inode, struct file *file)	\
 {									\
-	return single_open(file, __name ## _show, inode->i_private);	\
+	return single_open(file, __name ## _show, PDE_DATA(inode));	\
 }									\
 									\
 static const struct proc_ops __name ## _proc_ops = {			\
-- 
2.11.0


^ permalink raw reply related	[flat|nested] 5+ messages in thread

* Re: [PATCH] seq_file: fix passing wrong private data
  2021-10-29  3:26 [PATCH] seq_file: fix passing wrong private data Muchun Song
@ 2021-10-29  8:26 ` Christian Brauner
  2021-10-29  8:43   ` Muchun Song
  0 siblings, 1 reply; 5+ messages in thread
From: Christian Brauner @ 2021-10-29  8:26 UTC (permalink / raw)
  To: Muchun Song
  Cc: andriy.shevchenko, akpm, sfr, revest, adobriyan, linux-kernel,
	linux-fsdevel

On Fri, Oct 29, 2021 at 11:26:38AM +0800, Muchun Song wrote:
> DEFINE_PROC_SHOW_ATTRIBUTE() is supposed to be used to define a series
> of functions and variables to register proc file easily. And the users
> can use proc_create_data() to pass their own private data and get it
> via seq->private in the callback. Unfortunately, the proc file system
> use PDE_DATA() to get private data instead of inode->i_private. So fix
> it. Fortunately, there only one user of it which does not pass any
> private data, so this bug does not break any in-tree codes.
> 
> Fixes: 97a32539b956 ("proc: convert everything to "struct proc_ops"")
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
>  include/linux/seq_file.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
> index 103776e18555..72dbb44a4573 100644
> --- a/include/linux/seq_file.h
> +++ b/include/linux/seq_file.h
> @@ -209,7 +209,7 @@ static const struct file_operations __name ## _fops = {			\
>  #define DEFINE_PROC_SHOW_ATTRIBUTE(__name)				\
>  static int __name ## _open(struct inode *inode, struct file *file)	\
>  {									\
> -	return single_open(file, __name ## _show, inode->i_private);	\
> +	return single_open(file, __name ## _show, PDE_DATA(inode));	\
>  }									\
>  									\
>  static const struct proc_ops __name ## _proc_ops = {			\

Hm, after your change DEFINE_SHOW_ATTRIBUTE() and
DEFINE_PROC_SHOW_ATTRIBUTE() macros do exactly the same things, right?:

#define DEFINE_SHOW_ATTRIBUTE(__name)					\
static int __name ## _open(struct inode *inode, struct file *file)	\
{									\
	return single_open(file, __name ## _show, inode->i_private);	\
}									\
									\
static const struct file_operations __name ## _fops = {			\
	.owner		= THIS_MODULE,					\
	.open		= __name ## _open,				\
	.read		= seq_read,					\
	.llseek		= seq_lseek,					\
	.release	= single_release,				\
}

#define DEFINE_PROC_SHOW_ATTRIBUTE(__name)				\
static int __name ## _open(struct inode *inode, struct file *file)	\
{									\
	return single_open(file, __name ## _show, inode->i_private);	\
}									\

Can't you just replace the single instance where
DEFINE_PROC_SHOW_ATTRIBUTE with DEFINE_SHOW_ATTRIBUTE() and remove
DEFINE_PROC_SHOW_ATTRIBUTE completely?

Christian

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] seq_file: fix passing wrong private data
  2021-10-29  8:26 ` Christian Brauner
@ 2021-10-29  8:43   ` Muchun Song
  2021-10-29  8:50     ` Christian Brauner
  0 siblings, 1 reply; 5+ messages in thread
From: Muchun Song @ 2021-10-29  8:43 UTC (permalink / raw)
  To: Christian Brauner
  Cc: andriy.shevchenko, Andrew Morton, Stephen Rothwell, revest,
	Alexey Dobriyan, LKML, linux-fsdevel

On Fri, Oct 29, 2021 at 4:26 PM Christian Brauner
<christian.brauner@ubuntu.com> wrote:
>
> On Fri, Oct 29, 2021 at 11:26:38AM +0800, Muchun Song wrote:
> > DEFINE_PROC_SHOW_ATTRIBUTE() is supposed to be used to define a series
> > of functions and variables to register proc file easily. And the users
> > can use proc_create_data() to pass their own private data and get it
> > via seq->private in the callback. Unfortunately, the proc file system
> > use PDE_DATA() to get private data instead of inode->i_private. So fix
> > it. Fortunately, there only one user of it which does not pass any
> > private data, so this bug does not break any in-tree codes.
> >
> > Fixes: 97a32539b956 ("proc: convert everything to "struct proc_ops"")
> > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> > ---
> >  include/linux/seq_file.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
> > index 103776e18555..72dbb44a4573 100644
> > --- a/include/linux/seq_file.h
> > +++ b/include/linux/seq_file.h
> > @@ -209,7 +209,7 @@ static const struct file_operations __name ## _fops = {                   \
> >  #define DEFINE_PROC_SHOW_ATTRIBUTE(__name)                           \
> >  static int __name ## _open(struct inode *inode, struct file *file)   \
> >  {                                                                    \
> > -     return single_open(file, __name ## _show, inode->i_private);    \
> > +     return single_open(file, __name ## _show, PDE_DATA(inode));     \
> >  }                                                                    \
> >                                                                       \
> >  static const struct proc_ops __name ## _proc_ops = {                 \
>
> Hm, after your change DEFINE_SHOW_ATTRIBUTE() and
> DEFINE_PROC_SHOW_ATTRIBUTE() macros do exactly the same things, right?:

Unfortunately, they are not the same. The difference is the
operation structure, namely "struct file_operations" and
"struct proc_ops".

DEFINE_SHOW_ATTRIBUTE() is usually used by
debugfs while DEFINE_SHOW_ATTRIBUTE() is
used by procfs.

Thanks.

>
> #define DEFINE_SHOW_ATTRIBUTE(__name)                                   \
> static int __name ## _open(struct inode *inode, struct file *file)      \
> {                                                                       \
>         return single_open(file, __name ## _show, inode->i_private);    \
> }                                                                       \
>                                                                         \
> static const struct file_operations __name ## _fops = {                 \
>         .owner          = THIS_MODULE,                                  \
>         .open           = __name ## _open,                              \
>         .read           = seq_read,                                     \
>         .llseek         = seq_lseek,                                    \
>         .release        = single_release,                               \
> }
>
> #define DEFINE_PROC_SHOW_ATTRIBUTE(__name)                              \
> static int __name ## _open(struct inode *inode, struct file *file)      \
> {                                                                       \
>         return single_open(file, __name ## _show, inode->i_private);    \
> }                                                                       \
>
> Can't you just replace the single instance where
> DEFINE_PROC_SHOW_ATTRIBUTE with DEFINE_SHOW_ATTRIBUTE() and remove
> DEFINE_PROC_SHOW_ATTRIBUTE completely?
>
> Christian

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] seq_file: fix passing wrong private data
  2021-10-29  8:43   ` Muchun Song
@ 2021-10-29  8:50     ` Christian Brauner
  2021-10-29  9:16       ` Muchun Song
  0 siblings, 1 reply; 5+ messages in thread
From: Christian Brauner @ 2021-10-29  8:50 UTC (permalink / raw)
  To: Muchun Song
  Cc: andriy.shevchenko, Andrew Morton, Stephen Rothwell, revest,
	Alexey Dobriyan, LKML, linux-fsdevel

On Fri, Oct 29, 2021 at 04:43:40PM +0800, Muchun Song wrote:
> On Fri, Oct 29, 2021 at 4:26 PM Christian Brauner
> <christian.brauner@ubuntu.com> wrote:
> >
> > On Fri, Oct 29, 2021 at 11:26:38AM +0800, Muchun Song wrote:
> > > DEFINE_PROC_SHOW_ATTRIBUTE() is supposed to be used to define a series
> > > of functions and variables to register proc file easily. And the users
> > > can use proc_create_data() to pass their own private data and get it
> > > via seq->private in the callback. Unfortunately, the proc file system
> > > use PDE_DATA() to get private data instead of inode->i_private. So fix
> > > it. Fortunately, there only one user of it which does not pass any
> > > private data, so this bug does not break any in-tree codes.
> > >
> > > Fixes: 97a32539b956 ("proc: convert everything to "struct proc_ops"")
> > > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> > > ---
> > >  include/linux/seq_file.h | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
> > > index 103776e18555..72dbb44a4573 100644
> > > --- a/include/linux/seq_file.h
> > > +++ b/include/linux/seq_file.h
> > > @@ -209,7 +209,7 @@ static const struct file_operations __name ## _fops = {                   \
> > >  #define DEFINE_PROC_SHOW_ATTRIBUTE(__name)                           \
> > >  static int __name ## _open(struct inode *inode, struct file *file)   \
> > >  {                                                                    \
> > > -     return single_open(file, __name ## _show, inode->i_private);    \
> > > +     return single_open(file, __name ## _show, PDE_DATA(inode));     \
> > >  }                                                                    \
> > >                                                                       \
> > >  static const struct proc_ops __name ## _proc_ops = {                 \
> >
> > Hm, after your change DEFINE_SHOW_ATTRIBUTE() and
> > DEFINE_PROC_SHOW_ATTRIBUTE() macros do exactly the same things, right?:
> 
> Unfortunately, they are not the same. The difference is the
> operation structure, namely "struct file_operations" and
> "struct proc_ops".
> 
> DEFINE_SHOW_ATTRIBUTE() is usually used by
> debugfs while DEFINE_SHOW_ATTRIBUTE() is
> used by procfs.

Ugh, right, thanks for pointing that out. I overlooked the _proc_ops
appendix. Not sure what's right here. There seem to have been earlier
callers to DEFINE_PROC_SHOW_ATTRIBUTE() that relied on PDE_DATA() but
there's only one caller so that change wouldn't be too bad, I guess.

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] seq_file: fix passing wrong private data
  2021-10-29  8:50     ` Christian Brauner
@ 2021-10-29  9:16       ` Muchun Song
  0 siblings, 0 replies; 5+ messages in thread
From: Muchun Song @ 2021-10-29  9:16 UTC (permalink / raw)
  To: Christian Brauner
  Cc: andriy.shevchenko, Andrew Morton, Stephen Rothwell, revest,
	Alexey Dobriyan, LKML, linux-fsdevel

On Fri, Oct 29, 2021 at 4:50 PM Christian Brauner
<christian.brauner@ubuntu.com> wrote:
>
> On Fri, Oct 29, 2021 at 04:43:40PM +0800, Muchun Song wrote:
> > On Fri, Oct 29, 2021 at 4:26 PM Christian Brauner
> > <christian.brauner@ubuntu.com> wrote:
> > >
> > > On Fri, Oct 29, 2021 at 11:26:38AM +0800, Muchun Song wrote:
> > > > DEFINE_PROC_SHOW_ATTRIBUTE() is supposed to be used to define a series
> > > > of functions and variables to register proc file easily. And the users
> > > > can use proc_create_data() to pass their own private data and get it
> > > > via seq->private in the callback. Unfortunately, the proc file system
> > > > use PDE_DATA() to get private data instead of inode->i_private. So fix
> > > > it. Fortunately, there only one user of it which does not pass any
> > > > private data, so this bug does not break any in-tree codes.
> > > >
> > > > Fixes: 97a32539b956 ("proc: convert everything to "struct proc_ops"")
> > > > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> > > > ---
> > > >  include/linux/seq_file.h | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
> > > > index 103776e18555..72dbb44a4573 100644
> > > > --- a/include/linux/seq_file.h
> > > > +++ b/include/linux/seq_file.h
> > > > @@ -209,7 +209,7 @@ static const struct file_operations __name ## _fops = {                   \
> > > >  #define DEFINE_PROC_SHOW_ATTRIBUTE(__name)                           \
> > > >  static int __name ## _open(struct inode *inode, struct file *file)   \
> > > >  {                                                                    \
> > > > -     return single_open(file, __name ## _show, inode->i_private);    \
> > > > +     return single_open(file, __name ## _show, PDE_DATA(inode));     \
> > > >  }                                                                    \
> > > >                                                                       \
> > > >  static const struct proc_ops __name ## _proc_ops = {                 \
> > >
> > > Hm, after your change DEFINE_SHOW_ATTRIBUTE() and
> > > DEFINE_PROC_SHOW_ATTRIBUTE() macros do exactly the same things, right?:
> >
> > Unfortunately, they are not the same. The difference is the
> > operation structure, namely "struct file_operations" and
> > "struct proc_ops".
> >
> > DEFINE_SHOW_ATTRIBUTE() is usually used by
> > debugfs while DEFINE_SHOW_ATTRIBUTE() is
> > used by procfs.
>
> Ugh, right, thanks for pointing that out. I overlooked the _proc_ops
> appendix. Not sure what's right here. There seem to have been earlier
> callers to DEFINE_PROC_SHOW_ATTRIBUTE() that relied on PDE_DATA() but
> there's only one caller so that change wouldn't be too bad, I guess.

From my point of view, I think the macro is useful which can
simplify the code. However there is only one user of it. I suppose
few people know about it. For instance, the following ops can
become the user of it.

    cifs_mount_params_proc_ops
    nfsd_proc_ops
    rpc_proc_ops

Thanks.

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2021-10-29  9:17 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2021-10-29  3:26 [PATCH] seq_file: fix passing wrong private data Muchun Song
2021-10-29  8:26 ` Christian Brauner
2021-10-29  8:43   ` Muchun Song
2021-10-29  8:50     ` Christian Brauner
2021-10-29  9:16       ` Muchun Song

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).