From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793201915; b=BaVy/I44Xr7jzfryPdaKhrjIBmIgRGG1pmZSitn9LpGEtQubdUa4sLsVmlkMTvOW/Zig BAo+ZJsQWsBkEivHppgWbtyik4j+BLQKpX8Io+p5wYhboneK+LN7DXH3Wqnckm+fBD85H 3RxGKO36xYtReHb3HdAlfpArpl+UfGds+zYUHd3zzKLVuRiBEzMK+tKwhAjlw499sDRo9 RGKmEr6NzaieLdDAozO1DMm/GIPbotBTDK9VeHn7rna71rsKunUyPZinkerGe6xgFeYEk 9sI2eadRoKPBbk9VZsanVS6cNGF0ZRtmC5VFNodaNJeq9qy1M5zJKM/A1UIS+RWy1xg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793201915; h=Received:DKIM-Signature:Subject:To:Cc:From:Date:Message-ID: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=VoGxHDMmQVQPED5PcQ7qpL6bsIP2RmaYnCltmqGI4+Y=; b=lLeLHiut2g6kYZuMmWzfQnEhy94XLVj5ZW++pow104UfEQ6RvbgjeEW9CIKhwNkzorOQ dwR4ZstBml8vmuSh3GpsjR6hWo3ztfUlREryOoN5D/6NrmY6Tsf/7rFx8BEokNPhQEU1R 4wzdDlbdMyZrv5Sv6a39UqhxURJH495y9syoVwBcHJVPo2WpXSxt1YFhCeVKgyEoIdlBL DZ/xxMHvE4OY72AjOXXEJuQHqXvnP4vSUlIK2uQg8lohA8nO6nuj8ssVAc7oawfohsSz4 RMEKUR7f52QW+qpOeIyMSBctfEDJwspklFz/CSKerChhdBXD+fWOuBhV31j9ctP9oiA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=i3QtdBmu; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ADCEE606A31D for ; Wed, 28 Oct 2026 15:38:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=i3QtdBmu Received: by smtp.kernel.org (Postfix) with ESMTPSA id F073E1F01828; Wed, 28 Oct 2026 15:38:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793201914; bh=VoGxHDMmQVQPED5PcQ7qpL6bsIP2RmaYnCltmqGI4+Y=; h=Subject:To:Cc:From:Date; b=i3QtdBmu4nmc+SXV77Ta8i4QY2d2evSROIJ+iHQm9ih9SH8LEgzmsjZpPAg2nNjwD Ut1biraBKMiRol+T/Gl910eCKU4HzE3ZEXzEbSsyWnZXNn1DFjsA0jgnODVtmyMhuS ymN2H6CxTjuIUHskDEPbnTmwwn7U44dkEG8IpvIM= Subject: FAILED: patch "[PATCH] coredump: prevent TIF_NOTIFY_SIGNAL from interrupting" failed to apply to 5.10-stable tree To: brauner@kernel.org,oleg@redhat.com Cc: From: Date: Wed, 28 Oct 2026 16:38:21 +0100 Message-ID: <2026102821-detail-defiling-d6e2@gregkh> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list 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 5.10-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-5.10.y git checkout FETCH_HEAD git cherry-pick -x a58d647acfdc62561f3570d114025b3bf38ae41b # git commit -s git send-email --to '' --in-reply-to '2026102821-detail-defiling-d6e2@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From a58d647acfdc62561f3570d114025b3bf38ae41b Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Mon, 24 Aug 2026 14:08:17 +0200 Subject: [PATCH] coredump: prevent TIF_NOTIFY_SIGNAL from interrupting coredumps TIF_NOTIFY_SIGNAL is used to kick a task in uninterruptible sleep to return to userspace and run task work and then go back to sleep. This mechanism works well but breaks coredumps. dump_interrupted() only allows fatal signals to interrupt a coredump and the whole regular write path going to actual filesystems is impervious to TIF_NOTIFY_SIGNAL as well. However, both the usermodehelper pipe and the coredump socket will bail early on TIF_NOTIFY_SIGNAL. This affects the following codepaths: - coredump_sock_recv() -> unix_stream_read_generic() The request/ack handshake is abandoned before any coredump data is sent. - anon_pipe_write() returning -ERESTARTSYS Once the pipe is full this truncates the coredump. - unix_stream_sendmsg() returning -ERESTARTSYS Once the send buffer is full this truncates the coredump. - coredump_sock_wait() -> __kernel_read() This reports a failure that didn't happen. - wait_for_dump_helpers() -> wait_event_interruptible() This stops waiting for the coredump helpers. Such truncation is entirely invisible to userspace and all uapi bits still indicate that a successful coredump happened. A crashing process with a bunch of file backed mappings and io_uring thrown in loses most of the coredump data. If the NT_FILE note goes past PAGE_SIZE mappings it's gonzo. TIF_NOTIFY_SIGNAL is sent by io_uring for the common case. And it uses poll without sleeping so a completion callback runs task_work_add() from interrupt context against the task that submitted the request. This is the task that is running the coredump. Since that task hasn't set work_exited (it hasn't exited yet after all) TIF_NOTIFY_SIGNAL keeps reappearing. A coredumping task doesn't return to userspace. The task work is run at exit. So interrupting it doesn't buy anything and just loses the coredump which is quite valuable. Note that this isn't specific to io_uring. There's also klp_send_signals(), bpf_task_work_schedule_signal(), landlock's tsync and then technically, kthread_stop() and the printk kunit test set the bit raw. Link: https://patch.msgid.link/20260824-work-tif_notify_signal-v2-2-6609e42b3157@kernel.org Fixes: 12db8b690010 ("entry: Add support for TIF_NOTIFY_SIGNAL") Reviewed-by: Oleg Nesterov Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner (Amutable) diff --git a/fs/coredump.c b/fs/coredump.c index ac3cd74808c6..7c0f276c3e0d 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -1191,6 +1191,8 @@ void vfs_coredump(const kernel_siginfo_t *siginfo) if (coredump_wait(siginfo->si_signo, &core_state) < 0) return; + /* Task work must not cut the dump short, see signal_pending(). */ + guard(no_notify_signal)(); scoped_with_creds(cred) do_coredump(&cn, &cprm, &argv, &argc, binfmt); coredump_cleanup(&cn, &cprm);