From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Eric Biggers To: David Howells , Alexander Viro , linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Eric Biggers Subject: [PATCH 07/18] fs_context: fix double free of legacy_fs_context data Date: Sun, 8 Jul 2018 14:01:43 -0700 Message-Id: <20180708210154.10423-8-ebiggers3@gmail.com> In-Reply-To: <20180708210154.10423-1-ebiggers3@gmail.com> References: <20180708210154.10423-1-ebiggers3@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: From: Eric Biggers sys_fsmount() calls fc->ops->free() to free the data, zeroes ->fs_private, then proceeds to reuse the context. But legacy_fs_context doesn't use ->fs_private, so we need to handle zeroing it too; otherwise there's a double free of legacy_fs_context::{legacy_data,secdata}. Fixes: 8a2e54b8af88 ("vfs: Implement a filesystem superblock creation/configuration context") Signed-off-by: Eric Biggers --- fs/fs_context.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/fs_context.c b/fs/fs_context.c index 7a8d1ed34ae71..206256be9777e 100644 --- a/fs/fs_context.c +++ b/fs/fs_context.c @@ -504,6 +504,9 @@ static void legacy_fs_context_free(struct fs_context *fc) kfree(ctx->legacy_data); break; } + /* This doesn't use fs_private, so need to manually zero for fsmount */ + BUILD_BUG_ON(offsetof(struct legacy_fs_context, fc) != 0); + memset(fc + 1, 0, sizeof(*ctx) - sizeof(*fc)); } /* -- 2.18.0