proc: introduce proc_create_data to setup de->data

This set of patches fixes an proc ->open'less usage due to ->proc_fops flip in
the most part of the kernel code.  The original OOPS is described in the
commit 2d3a4e3666325a9709cc8ea2e88151394e8f20fc:

    Typical PDE creation code looks like:

    	pde = create_proc_entry("foo", 0, NULL);
    	if (pde)
    		pde->proc_fops = &foo_proc_fops;

    Notice that PDE is first created, only then ->proc_fops is set up to
    final value. This is a problem because right after creation
    a) PDE is fully visible in /proc , and
    b) ->proc_fops are proc_file_operations which do not have ->open callback. So, it's
       possible to ->read without ->open (see one class of oopses below).

    The fix is new API called proc_create() which makes sure ->proc_fops are
    set up before gluing PDE to main tree. Typical new code looks like:

    	pde = proc_create("foo", 0, NULL, &foo_proc_fops);
    	if (!pde)
    		return -ENOMEM;

    Fix most networking users for a start.

    In the long run, create_proc_entry() for regular files will go.

In addition to this, proc_create_data is introduced to fix reading from
proc without PDE->data. The race is basically the same as above.

create_proc_entries is replaced in the entire kernel code as new method
is also simply better.

This patch:

The problem is the same as for de->proc_fops.  Right now PDE becomes visible
without data set.  So, the entry could be looked up without data.  This, in
most cases, will simply OOPS.

proc_create_data call is created to address this issue.  proc_create now
becomes a wrapper around it.

Signed-off-by: Denis V. Lunev <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: "J. Bruce Fields" <[email protected]>
Cc: Alessandro Zummo <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Bartlomiej Zolnierkiewicz <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Bjorn Helgaas <[email protected]>
Cc: Chris Mason <[email protected]>
Acked-by: David Howells <[email protected]>
Cc: Dmitry Torokhov <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Grant Grundler <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Haavard Skinnemoen <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Bottomley <[email protected]>
Cc: Jaroslav Kysela <[email protected]>
Cc: Jeff Garzik <[email protected]>
Cc: Jeff Mahoney <[email protected]>
Cc: Jesper Nilsson <[email protected]>
Cc: Karsten Keil <[email protected]>
Cc: Kyle McMartin <[email protected]>
Cc: Len Brown <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Mauro Carvalho Chehab <[email protected]>
Cc: Mikael Starvik <[email protected]>
Cc: Nadia Derbey <[email protected]>
Cc: Neil Brown <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Osterlund <[email protected]>
Cc: Pierre Peiffer <[email protected]>
Cc: Russell King <[email protected]>
Cc: Takashi Iwai <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Trond Myklebust <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/proc/root.c b/fs/proc/root.c
index c741b45a5503..95117538a4f6 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -230,5 +230,5 @@ void pid_ns_release_proc(struct pid_namespace *ns)
 EXPORT_SYMBOL(proc_symlink);
 EXPORT_SYMBOL(proc_mkdir);
 EXPORT_SYMBOL(create_proc_entry);
-EXPORT_SYMBOL(proc_create);
+EXPORT_SYMBOL(proc_create_data);
 EXPORT_SYMBOL(remove_proc_entry);