From: ebiederm@xmission•com (Eric W. Biederman)
To: Ben Greear <greearb@candelatech•com>
Cc: "Denis V. Lunev" <den@openvz•org>,
Patrick McHardy <kaber@trash•net>,
Andrew Morton <akpm@linux-foundation•org>,
netdev@vger•kernel.org, bugme-daemon@bugzilla•kernel.org,
devzero@web•de, Robert Olsson <robert.olsson@its•uu.se>,
Pavel Emelyanov <xemul@openvz•org>
Subject: Re: [Bugme-new] [Bug 10737] New: pktgen procfs problem
Date: Mon, 19 May 2008 18:14:15 -0700 [thread overview]
Message-ID: <m1lk257p5k.fsf@frodo.ebiederm.org> (raw)
In-Reply-To: <48321AC2.90500@candelatech.com> (Ben Greear's message of "Mon, 19 May 2008 17:26:42 -0700")
Ben Greear <greearb@candelatech•com> writes:
> Denis V. Lunev wrote:
>
>> could you consider this preliminary patch? It fixes the problem for me
>> and Pavel agrees with it.
>>
>> The problem is that module_get is called for each file opening while
>> module_put is called only when /proc inode is destroyed. So, lets put
>> module counter if we are dealing with already initialised inode.
Acked-by: "Eric W. Biederman" <ebiederm@xmission•com>
>> ------------------------------------------------------------------------
>>
>> diff --git a/fs/proc/inode.c b/fs/proc/inode.c
>> index 6f4e8dc..b08d100 100644
>> --- a/fs/proc/inode.c
>> +++ b/fs/proc/inode.c
>> @@ -425,7 +425,8 @@ struct inode *proc_get_inode(struct super_block *sb,
> unsigned int ino,
>> }
>> }
>> unlock_new_inode(inode);
>> - }
>> + } else
>> + module_put(de->owner);
>> return inode;
>> out_ino:
>
> I just tested this and it seems to fix my problem (I applied this to 2.6.25
> kernel).
Looks good and it seems to follow the characterization.
proc_lookup -> proc_lookup_de -> proc_get_inode
Will happen each time a dentry is created for a name/inode.
Which is much easier now with multiple instances in
proc.
It looks like this bug an old bug that has existed since
commit e9543659715602e3180f00a227bb6db34141ac41
Author: Kirill Korotaev <dev@sw•ru>
Date: Sun Oct 30 15:02:26 2005 -0800
[PATCH] proc: fix of error path in proc_get_inode()
This patch fixes incorrect error path in proc_get_inode(), when module
can't be get due to being unloaded. When try_module_get() fails, this
function puts de(!) and still returns inode with non-getted de.
There are still unresolved known bugs in proc yet to be fixed:
- proc_dir_entry tree is managed without any serialization
- create_proc_entry() doesn't setup de->owner anyhow,
so setting it later manually is inatomic.
- looks like almost all modules do not care whether
it's de->owner is set...
Signed-Off-By: Denis Lunev <den@sw•ru>
Signed-Off-By: Kirill Korotaev <dev@sw•ru>
Signed-off-by: Andrew Morton <akpm@osdl•org>
Signed-off-by: Linus Torvalds <torvalds@osdl•org>
Eric
next prev parent reply other threads:[~2008-05-20 1:20 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-10737-10286@http.bugzilla.kernel.org/>
2008-05-17 21:10 ` [Bugme-new] [Bug 10737] New: pktgen procfs problem Andrew Morton
2008-05-18 1:39 ` Patrick McHardy
2008-05-18 4:56 ` Andrew Morton
2008-05-18 12:06 ` Patrick McHardy
2008-05-18 13:24 ` Patrick McHardy
2008-05-18 15:31 ` Patrick McHardy
2008-05-19 7:54 ` Denis V. Lunev
2008-05-19 10:34 ` Patrick McHardy
2008-05-20 0:26 ` Ben Greear
2008-05-20 1:14 ` Eric W. Biederman [this message]
2008-05-20 8:25 ` Robert Olsson
2008-05-19 21:34 ` Eric W. Biederman
2008-05-19 22:19 ` Ben Greear
2008-05-19 15:19 Alexey Dobriyan
-- strict thread matches above, loose matches on Subject: below --
2008-05-19 16:03 Alexey Dobriyan
2008-05-19 22:21 Alexey Dobriyan
2008-05-19 22:45 ` Robert Olsson
2008-05-20 21:57 Alexey Dobriyan
2008-05-20 21:17 ` Robert Olsson
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