[Cluster-devel] [PATCH] gfs2: fix potential NULL pointer dereference

[Cluster-devel] [PATCH] gfs2: fix potential NULL pointer dereference

[Michal Nazarewicz]

From: Michal Nazarewicz <mina86@mina86.com>

Commit [e66cf1610: GFS2: Use lockref for glocks] replaced call:
    atomic_read(&gi->gl->gl_ref) == 0
with:
    __lockref_is_dead(&gl->gl_lockref)
therefore changing how gl is accessed, from gi->gl to plan gl.
However, gl can be a NULL pointer, and so gi->gl needs to be
used instead (which is guaranteed not to be NULL because fo
the while loop checking that condition).

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
---
 fs/gfs2/glock.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index e66a800..c8420f7 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1899,7 +1899,8 @@ static int gfs2_glock_iter_next(struct gfs2_glock_iter *gi)
 			gi->nhash = 0;
 		}
 	/* Skip entries for other sb and dead entries */
-	} while (gi->sdp != gi->gl->gl_sbd || __lockref_is_dead(&gl->gl_lockref));
+	} while (gi->sdp != gi->gl->gl_sbd ||
+		 __lockref_is_dead(&gi->gl->gl_lockref));
 
 	return 0;
 }
-- 
1.8.4.1

[Cluster-devel] [PATCH] gfs2: fix potential NULL pointer dereference

[Steven Whitehouse]

Hi,

Yes, good catch. Thanks, I'll add it to the tree,

Steve.

On Tue, 2013-11-12 at 13:30 +0100, Michal Nazarewicz wrote:
> From: Michal Nazarewicz <mina86@mina86.com>
> 
> Commit [e66cf1610: GFS2: Use lockref for glocks] replaced call:
>     atomic_read(&gi->gl->gl_ref) == 0
> with:
>     __lockref_is_dead(&gl->gl_lockref)
> therefore changing how gl is accessed, from gi->gl to plan gl.
> However, gl can be a NULL pointer, and so gi->gl needs to be
> used instead (which is guaranteed not to be NULL because fo
> the while loop checking that condition).
> 
> Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
> ---
>  fs/gfs2/glock.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
> index e66a800..c8420f7 100644
> --- a/fs/gfs2/glock.c
> +++ b/fs/gfs2/glock.c
> @@ -1899,7 +1899,8 @@ static int gfs2_glock_iter_next(struct gfs2_glock_iter *gi)
>  			gi->nhash = 0;
>  		}
>  	/* Skip entries for other sb and dead entries */
> -	} while (gi->sdp != gi->gl->gl_sbd || __lockref_is_dead(&gl->gl_lockref));
> +	} while (gi->sdp != gi->gl->gl_sbd ||
> +		 __lockref_is_dead(&gi->gl->gl_lockref));
>  
>  	return 0;
>  }