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 142E91A0B12 for ; Mon, 30 Dec 2024 08:39:40 +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=1735547980; cv=none; b=lrybzthEATKbVVOP47lzgiwlJrER5ydX1P864hFU0gX+Jo6eMnE8pyKcrAkG35kfXZV4syTZ9GGS8NVz9rCZgWz/lUeT4HI4lRmH0eCjskDr9xtK4Pj1tWRrzJrunY/XjvSsEz4N/VB87QglQnwzENaQOIkJySK4WuEmzsSnJxM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735547980; c=relaxed/simple; bh=meZH4pTUmkJYPq+Pp5jT02IHkbj+BPa6c9bGbneCZ7g=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=r0S6jCXIZBNfdK7CNrPwCzXljhDrBjpC2KUKbfqBuO+pRTwG6F3mXnx+65b9oJmwva8HKE2MB9QbLrRm175wu1+3NyC1/oGwKUA1jTWj++Hv8AMfavbI6oykrTlr/XZJ1Qow4VhnOgS8Xu12UOqWm2fAk828QIPU03M8AG7pGrM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ywjZ27Ls; 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="ywjZ27Ls" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8508AC4CED0; Mon, 30 Dec 2024 08:39:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1735547979; bh=meZH4pTUmkJYPq+Pp5jT02IHkbj+BPa6c9bGbneCZ7g=; h=Subject:To:Cc:From:Date:From; b=ywjZ27LsY0YLayCTxP0op1nr1Yb4DBc7QHZcYLCikD6AcCowjVONNKbjJ4FPt235S oAOTDKdLPvp8pF1l/hTXnNpdH55+E/x1h+SrECcp4ZlFU7jEfVQtAXVMknNsXYB+kV l0ifVtHuFy4bsHr1FAcPnbqkBjzVfu5QHE0yPb3g= Subject: FAILED: patch "[PATCH] btrfs: fix use-after-free when COWing tree bock and tracing" failed to apply to 5.4-stable tree To: fdmanana@suse.com,dsterba@suse.com,wqu@suse.com Cc: From: Date: Mon, 30 Dec 2024 09:39:28 +0100 Message-ID: <2024123027-yeah-suitcase-41e7@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x 44f52bbe96dfdbe4aca3818a2534520082a07040 # git commit -s git send-email --to '' --in-reply-to '2024123027-yeah-suitcase-41e7@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 44f52bbe96dfdbe4aca3818a2534520082a07040 Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Wed, 11 Dec 2024 16:08:07 +0000 Subject: [PATCH] btrfs: fix use-after-free when COWing tree bock and tracing is enabled 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 diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 693dc27ffb89..185985a337b3 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -654,6 +654,8 @@ int btrfs_force_cow_block(struct btrfs_trans_handle *trans, goto error_unlock_cow; } } + + trace_btrfs_cow_block(root, buf, cow); if (unlock_orig) btrfs_tree_unlock(buf); free_extent_buffer_stale(buf); @@ -710,7 +712,6 @@ 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); @@ -751,12 +752,8 @@ 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);