ext4: fix potential use after free in __ext4_journal_stop

There is a use-after-free possibility in __ext4_journal_stop() in the
case that we free the handle in the first jbd2_journal_stop() because
we're referencing handle->h_err afterwards. This was introduced in
9705acd63b125dee8b15c705216d7186daea4625 and it is wrong. Fix it by
storing the handle->h_err value beforehand and avoid referencing
potentially freed handle.

Fixes: 9705acd63b125dee8b15c705216d7186daea4625
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Cc: stable@vger.kernel.org

diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c
index d4184318181878b023931078377ae17c9568a208..e770c1ee4613ed6084518f2ec9dca0ff9e53a29a 100644 (file)
--- a/fs/ext4/ext4_jbd2.c
+++ b/fs/ext4/ext4_jbd2.c
@@ -88,13 +88,13 @@ int __ext4_journal_stop(const char *where, unsigned int line, handle_t *handle)
                return 0;
        }
 
+       err = handle->h_err;
        if (!handle->h_transaction) {
-               err = jbd2_journal_stop(handle);
-               return handle->h_err ? handle->h_err : err;
+               rc = jbd2_journal_stop(handle);
+               return err ? err : rc;
        }
 
        sb = handle->h_transaction->t_journal->j_private;
-       err = handle->h_err;
        rc = jbd2_journal_stop(handle);
 
        if (!err)