Re: [patch] Btrfs: dereferencing free'd memory in panic message

[Dan Carpenter <dan.carpenter@oracle.com>]

On Fri, Jun 22, 2012 at 09:09:04AM -0400, Josef Bacik wrote:
> On 06/22/2012 03:14 AM, Dan Carpenter wrote:
> >We free "node" and then dereference it in the panic message on the next
> >line.  I considered moving the kfree() after the panic given that panic
> >can return under certain configurations, but in the end I decided it
> >doesn't matter if we leak a bit after a panic.
> >
> >Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> >
> >diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> >index 790f492..c50d80a 100644
> >--- a/fs/btrfs/relocation.c
> >+++ b/fs/btrfs/relocation.c
> >@@ -1239,7 +1239,6 @@ static int __must_check __add_reloc_root(struct btrfs_root *root)
> >  			      node->bytenr, &node->rb_node);
> >  	spin_unlock(&rc->reloc_root_tree.lock);
> >  	if (rb_node) {
> >-		kfree(node);
> >  		btrfs_panic(root->fs_info, -EEXIST, "Duplicate root found "
> >  			    "for start=%llu while inserting into relocation "
> >  			    "tree\n", node->bytenr);
> 
> Except btrfs_panic can not panic the box if it's mounted to not
> panic on errors, so we still need to do the kfree afterwards.
> Thanks,

Right.  I mentioned that in my change log, but I figured a one time
memory leak was the least of our concerns in that case.  I will
resend.  This should probably return -EEXIST here as well yes?

regards,
dan carpenter