ocfs2: fix potential use after free

ocfs2_get_dentry() calls iput(inode) to drop the reference count of
inode, and if the reference count hits 0, inode is freed.  However, in
this function, it then reads inode->i_generation, which may result in a
use after free bug.  Move the put operation later.

Link: http://lkml.kernel.org/r/[email protected]
Fixes: 781f200cb7a("ocfs2: Remove masklog ML_EXPORT.")
Signed-off-by: Pan Bian <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Joel Becker <[email protected]>
Cc: Junxiao Bi <[email protected]>
Cc: Joseph Qi <[email protected]>
Cc: Changwei Ge <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/fs/ocfs2/export.c b/fs/ocfs2/export.c
index 9f88188060db9c7fa59e6882ecf33b55cf921788..4bf8d5854b2711ebcac47c5c1f38d49f120d0eb5 100644 (file)
--- a/fs/ocfs2/export.c
+++ b/fs/ocfs2/export.c
@@ -125,10 +125,10 @@ check_err:
 
 check_gen:
        if (handle->ih_generation != inode->i_generation) {
-               iput(inode);
                trace_ocfs2_get_dentry_generation((unsigned long long)blkno,
                                                  handle->ih_generation,
                                                  inode->i_generation);
+               iput(inode);
                result = ERR_PTR(-ESTALE);
                goto bail;
        }