lkml.org 
[lkml]   [2007]   [Sep]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
SubjectRe: Two identical entries for "rtc" in /proc/devices
Date
On Saturday 15 September 2007, Andrew Morton wrote:
> On Sat, 15 Sep 2007 11:50:21 -0700 David Brownell <david-b@pacbell.net> wrote:
>
> > > On Thu, 06 Sep 2007 18:23:22 -0400 Chuck Ebbert <cebbert@redhat.com> wrote:
> > >
> > > > # ls -li
> > > > total 0
> > > > 4026532007 -r--r--r-- 1 root root 0 Sep 6 18:18 nvram
> > > > 4026532067 -r--r--r-- 1 root root 0 Sep 6 18:18 rtc
> > > > 4026532067 -r--r--r-- 1 root root 0 Sep 6 18:18 rtc
> > > > 4026532056 -rw-r--r-- 1 root root 0 Sep 6 18:18 snd-page-alloc
> > >
> > > ...
> >
> > Semes pretty clear that this must be procfs itself...
> > when a filesystem sees a name in a directory, it should
> > refuse to make another file with the same name. And it
> > should *never* reuse inode numbers...
>
> ...
>
> procfs can reject the attempt to create the file, but the bottom line
> is that two different callsites are trying to create the same file. One
> of those callsites needs fixing?

Both of those call sites have code to handle procfs rejecting
the file creation; nothing to fix. And anyway, there's no way
this is a *caller* bug!

The missing step seems to be that proc_register() doesn't bother
to check whether there's already an entry for that file. Which
is what the appended *UNTESTED* patch does (it compiles though).

- Dave

--- g26.orig/fs/proc/generic.c 2007-09-18 22:08:44.000000000 -0700
+++ g26/fs/proc/generic.c 2007-09-18 22:14:07.000000000 -0700
@@ -521,10 +521,11 @@ static const struct inode_operations pro
.setattr = proc_notify_change,
};

-static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp)
+static int proc_register(struct proc_dir_entry *dir, struct proc_dir_entry *dp)
{
unsigned int i;
-
+ struct proc_dir_entry *de;
+
i = get_inode_number();
if (i == 0)
return -EAGAIN;
@@ -547,6 +548,16 @@ static int proc_register(struct proc_dir
}

spin_lock(&proc_subdir_lock);
+
+ for (de = dir->subdir; de ; de = de->next) {
+ if (de->namelen != dp->namelen)
+ continue;
+ if (!memcmp(de->name, dp->name, de->namelen)) {
+ spin_unlock(&proc_subdir_lock);
+ return -EEXIST;
+ }
+ }
+
dp->next = dir->subdir;
dp->parent = dir;
dir->subdir = dp;
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-09-19 07:59    [from the cache]
©2003-2011 Jasper Spaans