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 4DDD015A86A; Mon, 6 Jan 2025 15:27:27 +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=1736177247; cv=none; b=iRMf/dnnI9YszY9ocUXJ7KayBcBzgK+HI1MUaTM8kd66u+5sEb83C64KE3onJ6FkuVHbLsGo1f0NV3Q9YSqvfn99aA5Cadj3W1bicqNr3jaQDzGmfEa7BPlhhEpaSp6Jg6zRge3Him6sM3ie8LbGHALMn9vIXa35pNejfu8ATLM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736177247; c=relaxed/simple; bh=X33T8Fiva+Ey9/rL4aJOt/KcdeNP9D53+0kaIrHKV0c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HNyu1v2RebBuHOgSbevp6xFxNrZLW9ZAZYXCoJeaV2jj0j/DI/qg7QL5vJPqf2YGjI4640vEkHlp8xnqCuBdmZb5pB+9KTA3Pwyu3O8zbsyK2oH8JHflKEJJWo71vGp7ZHvsgQM97tv347AXlxyfnZqMD1S8NFcqNAWUV5IOiRg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Byp8w901; 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="Byp8w901" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C646FC4CED2; Mon, 6 Jan 2025 15:27:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1736177247; bh=X33T8Fiva+Ey9/rL4aJOt/KcdeNP9D53+0kaIrHKV0c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Byp8w901fyUPqI/gGyiqMe6XTKoUfR8nVdeJTiaUV/w/T49yAk1o6p2e0Bf4n0MLU 2nO9q5yNOOznF1ELToKUNK0lQpo3vQ6iN+myAKDfHZIeo/mzB+l246sacT+vCoigT0 nhOSk84QZz3mUUWsR92WjUMGlFE77QSrxuNrZisk= 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 6.6 101/222] btrfs: fix use-after-free when COWing tree bock and tracing is enabled Date: Mon, 6 Jan 2025 16:15:05 +0100 Message-ID: <20250106151154.418519689@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250106151150.585603565@linuxfoundation.org> References: <20250106151150.585603565@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-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 62032d3fda85..4b21ca49b666 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -660,6 +660,8 @@ int btrfs_force_cow_block(struct btrfs_trans_handle *trans, return ret; } } + + trace_btrfs_cow_block(root, buf, cow); if (unlock_orig) btrfs_tree_unlock(buf); free_extent_buffer_stale(buf); @@ -711,7 +713,6 @@ 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); @@ -752,12 +753,8 @@ 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