From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6A20C14D28C; Mon, 6 Jan 2025 15:20:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736176858; cv=none; b=TNM99IiBO9SkLGbXM9RPNY0ex2nnKObbi/h3p5wogxFLLZa+FlfbVvhRj/nNu6ZwKnjjmSI/stRLr4/7aEWP3wQ02Wd0Ji6Sdy9jtk8GZ6Nktd+dNSeIu74ow4aiLOd7GoVX7lv9s41Jzs6CFy2SpVrFz/vqBLxBwNfrfv6JOyc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736176858; c=relaxed/simple; bh=KCbgHx+OZmqo2WCgLmxsf3kIyjoFNrkGGniv/9Gof/s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qFJWqkXRYm2yqF76C7qs9zYqTmThTMtMxoNZfpl10z4JQsgYVX+/Bk53APqiol9hQAKmE/ay9iD3JtaL9PrQQqu0tWWoSWX0QD6wthtWldXWXPmsR4ev0rZByZ5kiu3mh7go9WnTPtgM5PazS293Sycrdo/+20UAEw50CybqNS0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Z6cf0hg9; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Z6cf0hg9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 91FEFC4CED2; Mon, 6 Jan 2025 15:20:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1736176858; bh=KCbgHx+OZmqo2WCgLmxsf3kIyjoFNrkGGniv/9Gof/s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Z6cf0hg94oO4+4haLdUjZFF6W6Uxo79t3N79Vor06EVhFgYf8ATszQwW87iki8uO8 a3c26KJrDkhada9L8SqlBh6wJR4npzGUbxpwj4tN9vdoA7nZx9oFT028bK4T+I/YS2 ZsuevVsSlua/zJsXNn8J+JanYhhS9Dveh6lsOmEw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+8517da8635307182c8a5@syzkaller.appspotmail.com, Qu Wenruo , Filipe Manana , David Sterba , Sasha Levin Subject: [PATCH 6.1 52/81] btrfs: fix use-after-free when COWing tree bock and tracing is enabled Date: Mon, 6 Jan 2025 16:16:24 +0100 Message-ID: <20250106151131.397118529@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250106151129.433047073@linuxfoundation.org> References: <20250106151129.433047073@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Filipe Manana [ Upstream commit 44f52bbe96dfdbe4aca3818a2534520082a07040 ] When a COWing a tree block, at btrfs_cow_block(), and we have the tracepoint trace_btrfs_cow_block() enabled and preemption is also enabled (CONFIG_PREEMPT=y), we can trigger a use-after-free in the COWed extent buffer while inside the tracepoint code. This is because in some paths that call btrfs_cow_block(), such as btrfs_search_slot(), we are holding the last reference on the extent buffer @buf so btrfs_force_cow_block() drops the last reference on the @buf extent buffer when it calls free_extent_buffer_stale(buf), which schedules the release of the extent buffer with RCU. This means that if we are on a kernel with preemption, the current task may be preempted before calling trace_btrfs_cow_block() and the extent buffer already released by the time trace_btrfs_cow_block() is called, resulting in a use-after-free. Fix this by moving the trace_btrfs_cow_block() from btrfs_cow_block() to btrfs_force_cow_block() before the COWed extent buffer is freed. This also has a side effect of invoking the tracepoint in the tree defrag code, at defrag.c:btrfs_realloc_node(), since btrfs_force_cow_block() is called there, but this is fine and it was actually missing there. Reported-by: syzbot+8517da8635307182c8a5@syzkaller.appspotmail.com Link: https://lore.kernel.org/linux-btrfs/6759a9b9.050a0220.1ac542.000d.GAE@google.com/ CC: stable@vger.kernel.org # 5.4+ Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/ctree.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index a02b41106257..c7171b286de7 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -520,6 +520,8 @@ int btrfs_force_cow_block(struct btrfs_trans_handle *trans, btrfs_free_tree_block(trans, btrfs_root_id(root), buf, parent_start, last_ref); } + + trace_btrfs_cow_block(root, buf, cow); if (unlock_orig) btrfs_tree_unlock(buf); free_extent_buffer_stale(buf); @@ -571,7 +573,6 @@ noinline int btrfs_cow_block(struct btrfs_trans_handle *trans, { struct btrfs_fs_info *fs_info = root->fs_info; u64 search_start; - int ret; if (unlikely(test_bit(BTRFS_ROOT_DELETING, &root->state))) { btrfs_abort_transaction(trans, -EUCLEAN); @@ -612,12 +613,8 @@ noinline int btrfs_cow_block(struct btrfs_trans_handle *trans, * Also We don't care about the error, as it's handled internally. */ btrfs_qgroup_trace_subtree_after_cow(trans, root, buf); - ret = btrfs_force_cow_block(trans, root, buf, parent, parent_slot, - cow_ret, search_start, 0, nest); - - trace_btrfs_cow_block(root, buf, *cow_ret); - - return ret; + return btrfs_force_cow_block(trans, root, buf, parent, parent_slot, + cow_ret, search_start, 0, nest); } ALLOW_ERROR_INJECTION(btrfs_cow_block, ERRNO); -- 2.39.5