Re: [Bugme-new] [Bug 10737] New: pktgen procfs problem

Ben Greear [off-list ref] writes:

Denis V. Lunev wrote:

quoted

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" <redacted>

quoted

------------------------------------------------------------------------

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,

quoted

 			}
 		}
 		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 [off-list ref]
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 [off-list ref]
    Signed-Off-By: Kirill Korotaev [off-list ref]
    Signed-off-by: Andrew Morton [off-list ref]
    Signed-off-by: Linus Torvalds [off-list ref]

Eric