2011-06-08 06:43:26

by Dan Carpenter

Subject: [patch] NFS: using freed variable in debug code

"ds" gets dereferenced after a kfree in the debug output. I just
moved the free down a line.

Signed-off-by: Dan Carpenter <[email protected]>

diff --git a/fs/nfs/nfs4filelayoutdev.c b/fs/nfs/nfs4filelayoutdev.c
index 77c171e..c63bbce 100644
--- a/fs/nfs/nfs4filelayoutdev.c
+++ b/fs/nfs/nfs4filelayoutdev.c
@@ -362,11 +362,11 @@ nfs4_pnfs_ds_add(struct list_head *dsaddrs, gfp_t gfp_flags)
__func__, tmp_ds->ds_remotestr, remotestr);
}
kfree(remotestr);
- kfree(ds);
atomic_inc(&tmp_ds->ds_count);
dprintk("%s data server %s found, inc'ed ds_count to %d\n",
__func__, ds->ds_remotestr,
atomic_read(&tmp_ds->ds_count));
+ kfree(ds);
ds = tmp_ds;
}
spin_unlock(&nfs4_ds_cache_lock);

2011-06-08 14:30:03

by Weston Andros Adamson

Subject: Re: [patch] NFS: using freed variable in debug code

Oops, good catch!

Actually, we can leave the kfree() where it is. Using ds->ds_remotestr in the dprintk is a typo - It should be tmp_ds->ds_remotestr.

-dros

On Jun 8, 2011, at 2:43 AM, Dan Carpenter wrote:

> "ds" gets dereferenced after a kfree in the debug output. I just
> moved the free down a line.
>
> Signed-off-by: Dan Carpenter <[email protected]>
>
> diff --git a/fs/nfs/nfs4filelayoutdev.c b/fs/nfs/nfs4filelayoutdev.c
> index 77c171e..c63bbce 100644
> --- a/fs/nfs/nfs4filelayoutdev.c
> +++ b/fs/nfs/nfs4filelayoutdev.c
> @@ -362,11 +362,11 @@ nfs4_pnfs_ds_add(struct list_head *dsaddrs, gfp_t gfp_flags)
> __func__, tmp_ds->ds_remotestr, remotestr);
> }
> kfree(remotestr);
> - kfree(ds);
> atomic_inc(&tmp_ds->ds_count);
> dprintk("%s data server %s found, inc'ed ds_count to %d\n",
> __func__, ds->ds_remotestr,
> atomic_read(&tmp_ds->ds_count));
> + kfree(ds);
> ds = tmp_ds;
> }
> spin_unlock(&nfs4_ds_cache_lock);
> --
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2011-06-09 18:08:10

by Dan Carpenter

Subject: [patch v2] NFS: fix debug message

"tmp_ds" was intended here instead of "ds". Also "ds" was already
freed.

Signed-off-by: Dan Carpenter <[email protected]>
---
v1 fixed the user-after-free but left the message incorrect.

diff --git a/fs/nfs/nfs4filelayoutdev.c b/fs/nfs/nfs4filelayoutdev.c
index 77c171e..ed388aa 100644
--- a/fs/nfs/nfs4filelayoutdev.c
+++ b/fs/nfs/nfs4filelayoutdev.c
@@ -365,7 +365,7 @@ nfs4_pnfs_ds_add(struct list_head *dsaddrs, gfp_t gfp_flags)
kfree(ds);
atomic_inc(&tmp_ds->ds_count);
dprintk("%s data server %s found, inc'ed ds_count to %d\n",
- __func__, ds->ds_remotestr,
+ __func__, tmp_ds->ds_remotestr,
atomic_read(&tmp_ds->ds_count));
ds = tmp_ds;
}