gfs2: Refcounting fix in gfs2_thaw_super

It turns out that the .freeze_super and .thaw_super operations require
the filesystem to manage the superblock refcount itself.  We are using
the freeze_super() and thaw_super() helpers to mostly take care of that
for us, but this means that the superblock may no longer be around by
when thaw_super() returns, and gfs2_thaw_super() will then access freed
memory.  Take an extra superblock reference in gfs2_thaw_super() to fix
that.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 6b45b7866212482e4a5b7a5798215d2f3ab0c7a2..ae92ae1203d8fba772a070694f3467b9133f5877 100644 (file)
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -819,6 +819,7 @@ static int gfs2_thaw_super(struct super_block *sb, enum freeze_holder who)
                return -EINVAL;
        }
 
+       atomic_inc(&sb->s_active);
        gfs2_freeze_unlock(&sdp->sd_freeze_gh);
 
        error = gfs2_do_thaw(sdp);
@@ -828,6 +829,7 @@ static int gfs2_thaw_super(struct super_block *sb, enum freeze_holder who)
                clear_bit(SDF_FROZEN, &sdp->sd_flags);
        }
        mutex_unlock(&sdp->sd_freeze_mutex);
+       deactivate_super(sb);
        return error;
 }