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=1793826791; b=YBzsz1RNKre5OIlnEW04HHTU8CvbXvnRAlJYqeecwf218PeckHDNdGPSfS9eM166MY7B vpm+sewfr0UANh4+d5ouewF5ru+oEpnsCEJkofU1NvFNMlWOahlB0eCjBrLy2IkJld6wL y57zFZqKFQTgMAhRSfj0nqdYDzZ9NciVs76VrKkJwIXEU6Vya/KkcyY+OgSYu4KkHyGLF 0w2yUUAdoR5GaVHOp3cEDagXZHCvCysPyE3skptb3k8HbP+BhnXAoeOrRctxnfgUVSE7R Oq6yz1sx6c2bpKc0UwxC0zIGF7+Btu9gWWeGwnh3lrJIEPLTy/d5E52QecwQtIitjUw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793826791; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=uTw2DiBW9l42YAemMchIWlcGftJB2+wgbO/sXMEeHIk=; b=UqWobq4SgrSZC9UKIXVX/giMNGQSUNrrZR+L1EkeLTHc9aBnhVyyWSVF7zxqe1WKhQS2 3It/8OlKNPOgqN1reQyyvk0x2E//v3KacCgXMr84j76SrfZEX2FXVhQY4iwInTyRt96av 2knrNB0Tgc1hzwEua4f9BgdRBBqEl9mm1fMHg2FrBh5LqFnpvuTZeer4sJaEyF/zVFtWc 58a64cAQdqb0lQdrvSkZfHILl61lVJwjHWs2vFX/bfvxIFetrKY0uuED7Py9IT4uJzqYw dUh3VCW+x8OxgrwR1bvBnn5KC8K7ziMwva74IBOb4NqMPoSzZy2cW2yqIrlq/lRHdKw== 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=BP1ahgna; 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 7A4DF6071A00; Wed, 4 Nov 2026 21:13:11 +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=BP1ahgna Received: by smtp.kernel.org (Postfix) with ESMTPSA id E34EF1F00A15; Wed, 4 Nov 2026 21:13:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793826791; bh=uTw2DiBW9l42YAemMchIWlcGftJB2+wgbO/sXMEeHIk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=BP1ahgnamgSGWGHby9f4xLBllKSUu/FArT/4ddfKK66VcKTBsnVmqgvfTDNTBztuz tPsRARkIwpfvjLH97txmCXRbyx/9z/YZLTExuSKiuEYoMsStZY/Hqt07wp+se4+AY/ HALHSkj38bmUXoY6tr48JGM3XlFfU26RMZmc84xI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Oleg Nesterov , "Christian Brauner (Amutable)" , Sasha Levin Subject: [PATCH 6.18 0011/1005] coredump: prevent TIF_NOTIFY_SIGNAL from interrupting coredumps Date: Wed, 4 Nov 2026 15:55:44 -0500 Message-ID: <20261104211043.854490153@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261104211043.516122098@linuxfoundation.org> References: <20261104211043.516122098@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Christian Brauner [ Upstream commit a58d647acfdc62561f3570d114025b3bf38ae41b ] 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) [ sashal: adjusted context for inline coredump handling with override_creds() instead of scoped_with_creds(). ] Signed-off-by: Sasha Levin --- fs/coredump.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/coredump.c b/fs/coredump.c index 3e927378bf5bf..b3cc7c0531ee1 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -1131,6 +1131,8 @@ 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)(); old_cred = override_creds(cred); if (!coredump_parse(&cn, &cprm, &argv, &argc)) { -- 2.53.0