From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.215.199 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793051570; b=gzviiHX9NO7SvJiJNYylJZMkVxxNWOl6P+b7sCm2ScLTEHxa64yyIXUAs47Ek57pa+xa 4T58OkTOv1tLGSxTGdxPFiXblNQaQw0FA52BUT2vXxdpXYuIoh4BAhhHYoQq2QwWOZvxz GGm/WHC9mLsH7nFGAoz3xqtQLQ1RBUcxfzczh54gC6MOnQba9zlMsJIqID/tv9P6vbmaV YN+tPpRA773gW6z67YmTzqWpmQ/2PAGQKFNpsPJYhTtVx/uVW9/pYeUk5+mrFKSwy4qHS rdx2h7XERDB1R98etKQmLXfzr4dhqNrbBJ7mq6VB9MJ28/2WkUacP+6AylsO7KxSmVQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793051570; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Received:Date:In-Reply-To: Mime-Version:References:X-Mailer:Message-ID:Subject:From:To:Cc: Content-Type; bh=/8L34Uc9Xo1d4oJ1WUUvtNMd/yh9NNapi89sPDAfm6Y=; b=DXgFwEWat/4pvlpGFy7Hf84QgpuvZkQguCI5DlEhvcq5ZzLZxG4QE6XgTVqYMw9wekRw 1abslGndEnYjGhMbSLfq+EKCmThME9h7KA9mJWU/kmQXsIOdjActKLKzrp0Qm1goDjHsj RF9Qss2GZlx5uVZ/b2AWzcLWpWe3obyz6Ob4fy/BQ+00E7tN0wlTlg+Q28FGeibaJTYmm JrQtHEBDGwtFwqhgXrs+v6jCRErkxliidDhK7+ptxv2kYT8FKhV1Um9D1FnZBNS88H2Gv m8lolxXOXXawCP0IMwjDYy/DXUzPXO91+xEp0cyf0sWpiYDALoql9q2RWB0u0AJvBKg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=google.com; spf=pass smtp.mailfrom=flex--jthoughton.bounces.google.com; dkim=pass header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20251104 header.b=fU7gA7Dl; arc=none smtp.remote-ip=209.85.215.199 Received: from mail-pg1-f199.google.com (mail-pg1-f199.google.com [209.85.215.199]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5681260A2622 for ; Mon, 26 Oct 2026 21:52:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 5681260A2622 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jthoughton.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20251104 header.b=fU7gA7Dl Received: by mail-pg1-f199.google.com with SMTP id 41be03b00d2f7-cd68bf391e1so2190145a12.3 for ; Mon, 26 Oct 2026 14:52:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1793051570; x=1793656370; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=/8L34Uc9Xo1d4oJ1WUUvtNMd/yh9NNapi89sPDAfm6Y=; b=fU7gA7DljvCqdvdMpaU2dp8kIrEccZFKOmWnfW6sw+A054S6dlNZugZLhIYYcfiePQ hsLgQW99gw7/40gSfJI6nU0rtnm0+1dPDbRaUoY665tdkjNVHr2UFbegtIbotfU9v9/A uK7QOilz2oAfaWXl/tsF91D3vAUMVrFCU+UmdWgUF2++tfRICFcImVM7cH8b81croIe/ 3gbPbeDpIxRnPDaXaoU22kL/RynJy6L0hYZfzyDRTzTeCDcQlDb8FUzF1BEGuZLmjKzH eeONqBOhxrAFnMU8HI0VT7oOvpOxL8LajgaOKQMUvvRXhW0M5pmi7s9QGStFhbTf6Lb8 9JRA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1793051570; x=1793656370; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=/8L34Uc9Xo1d4oJ1WUUvtNMd/yh9NNapi89sPDAfm6Y=; b=skJETCk3ntMN8ktswrNke5ZQC0al2x0ycdkhggLKK9VfIlH0e8Ij8zXOy9kZ5Ohmnk sjj4eZejDU6/ELYbip/q7k33cdhwoB+GykK06iMwPLmgt+T3Fwo6NTnj4lvdP8Pqus5K vTS3F3vRBuYR06+flMnN3xkLv3/eE6nKTFiBPQR7FfjMf8tnhRMvbts6FT7S4JvWYr0H 9RVZPqlfJrBN8m8JFs1kEycjbBZrjvJPIB2q5F6vtXyxQPjDFPXeqfYOZwRGynEAKj3N dIYR9G5l94LNZaMcDpUpoGDHn8tKc+klqMocH/IZY/NIGO0zbR7hhHHvLzwTosiT718j 4wbw== X-Forwarded-Encrypted: i=1; AKwUvBxjxgL0L5D/DtouRLhP3SV4SCvjdxNxQJCRf6mAdMnq2RHLUc2QxgetriqvlbUq9Gmi74ZLenMSbqOHR8g=@vger.kernel.org X-Gm-Message-State: AFq9FYLSZDsFOrutOxVh9wvxRJ/j0YhAGrLMh4NfvKB3cI2BsJisy2dS ni8uqD4xLpBop+0JkvIMtvvmXsSLEGpBsEtGYjZ0/2WinUmhfq5uSDMlVdUSU6O7NxQ49zNweq0 D0nHEym/hIZyBz/7cW7M31A== X-Received: from pjbme4.prod.google.com ([2002:a17:90b:17c4:b0:3ae:349e:2bcd]) (user=jthoughton job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:35cc:b0:3ad:1b31:92d8 with SMTP id 98e67ed59e1d1-3adeb16ecffmr5865801a91.60.1793051569572; Mon, 26 Oct 2026 14:52:49 -0700 (PDT) Date: Mon, 26 Oct 2026 21:52:18 +0000 In-Reply-To: <20261026215226.3713941-1-jthoughton@google.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 References: <20261026215226.3713941-1-jthoughton@google.com> X-Mailer: git-send-email 2.56.0.307.g5fe7bd680c-goog Message-ID: <20261026215226.3713941-3-jthoughton@google.com> Subject: [RFC PATCH 02/10] btrfs: Don't copy encoded read data to user memory when canceled From: James Houghton To: Andrew Morton , Alexander Viro Cc: Thomas Gleixner , Peter Zijlstra , Kees Cook , Arnd Bergmann , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Sean Christopherson , Paolo Bonzini , Jim Mattson , Jens Axboe , Pavel Begunkov , "James E.J. Bottomley" , "Martin K. Petersen" , David Sterba , Chris Mason , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Josh Poimboeuf , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, kvm@vger.kernel.org, io-uring@vger.kernel.org, linux-scsi@vger.kernel.org, linux-btrfs@vger.kernel.org, bpf@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, James Houghton Content-Type: text/plain; charset="UTF-8" btrfs_uring_read_finished() copies the data of an io_uring encoded read to the submitter's buffers with copy_page_to_iter(). It runs as io_uring task work, but io_uring may also run it with tw.cancel set from other contexts when the submitting task can't run it: from a kworker when the submitting task has exited (io_tctx_fallback_work()), or from io_cancel_local_task_work() when a DEFER_TASKRUN ring is torn down. In a kworker, current->mm is NULL, and the copy does not reliably fail: the user half of the address space belongs to whatever mm happens to be lazily loaded, if any, so the data may be written into an unrelated process. Don't copy the data when the task work is canceled, and complete the command with -ECANCELED. Fixes: 34310c442e17 ("btrfs: add io_uring command for encoded reads (ENCODED_READ ioctl)") Signed-off-by: James Houghton --- fs/btrfs/ioctl.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index f3e2afe221be..d9044fbd9547 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -4609,6 +4609,16 @@ static void btrfs_uring_read_finished(struct io_tw_req tw_req, io_tw_token_t tw) goto out; } + /* + * If the request is being canceled, e.g. because the submitting task + * has exited, this may run from a kworker or in a different task, so + * don't copy the data to the submitter's buffers. + */ + if (unlikely(tw.cancel)) { + ret = -ECANCELED; + goto out; + } + if (priv->compressed) { index = 0; page_offset = 0; -- 2.56.0.307.g5fe7bd680c-goog