Re: [PATCH] [-mm] FS: file name must be unique in the same dir inprocfs

From: Zhang Rui
Date: Tue Sep 11 2007 - 02:39:27 EST


On Mon, 2007-09-10 at 15:49 +0800, Andrew Morton wrote:
> On Mon, 20 Aug 2007 23:50:05 +0800 Zhang Rui <rui.zhang@xxxxxxxxx>
> wrote:
>
> > Hi, Oliver,
> > Thanks for your comments,
> >
> > On Mon, 2007-08-20 at 18:45 +0800, Oliver Neukum wrote:
> > > Am Montag 20 August 2007 schrieb Zhang Rui:
> > > > Files name must be unique in the same directory.
> > > >
> > > > Bug is reported here:
> > > > http://bugzilla.kernel.org/show_bug.cgi?id=8798
> > >
> > > Then I'd say fix the callers.
> > But at least the callers need to be told that something is wrong
> first.
> >
> > > This will paper over bugs.
> > Hmm, what kind of bugs?
> > callers always need to check the return value when calling
> > proc_mkdir/create_proc_entry, don't they?
> >
>
> Yes, but there's some risk that such a change will cause a
> presently-working system to stop working. It's quite likely, if that
> system is checking the procfs-creation return value.
Yes, that's true.
I checked several systems and didn't find any similar problems.
I think this situation is rare.
Besides, duplicate names are totally unusable for user space.
We should fix this kind of bugs ASAP if there are any.

> So I think it'd be best if we were to detect the duplication and print
> a
> warning (which should include, if possible, the full pathname and a
> dump_stack()) and then the code should proceed as normal: permit the
> duplicated entry and return success.
> Then, when such duplicates are reported, we can work out what to do
> about
> them on a case-by-case basis.
Please review the patch below. :)
dump_stack is enough to debug the problem, so only the current duplicate
file names are printed out instead of the full pathname.

From: Zhang Rui <rui.zhang@xxxxxxxxx>
File name should be unique in the same directory.

In order to keep the back-compatibility, only a warning is given
currently, but actions must be taken to fix it when such duplicates
are detected.

Bug report and a simple fix can be found here:
http://bugzilla.kernel.org/show_bug.cgi?id=8798

Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx>
---
fs/proc/generic.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

Index: linux-2.6/fs/proc/generic.c
===================================================================
--- linux-2.6.orig/fs/proc/generic.c
+++ linux-2.6/fs/proc/generic.c
@@ -523,6 +523,7 @@ static const struct inode_operations pro

static int proc_register(struct proc_dir_entry * dir, struct
proc_dir_entry * dp)
{
+ struct proc_dir_entry *tmp = NULL;
unsigned int i;

i = get_inode_number();
@@ -547,11 +548,22 @@ static int proc_register(struct proc_dir
}

spin_lock(&proc_subdir_lock);
+
+ for (tmp = dir->subdir, i = 0; tmp && !i; tmp = tmp->next)
+ if (!strcmp(dp->name, tmp->name))
+ i = 1;
+
dp->next = dir->subdir;
dp->parent = dir;
dir->subdir = dp;
spin_unlock(&proc_subdir_lock);

+ if (i) {
+ printk(KERN_WARNING
+ "Duplicate file names \"%s\" detected.", dp->name);
+ dump_stack();
+ }
+
return 0;
}

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