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b=Pkd7btEqIVMy32yBV4H5W3zqb0fa1P5MfRbFowvOs834XAVar1yMYQtnIUwOzDul1i pyfoPghmpvDZ1i/jTR8loJ1iJjh56K1MnLpSY3uzPRpnUTGY8h37rv4Se2cpX4taR4Ng bVR1m1XeQATNy+Of5N2rLkX4KjhSyd7Q43gdWq5SDj8Q5QwAfkTIwpnkYzzVb9N+rTEz OIpLJiDfoJKXWpHkuelDMU0w9//89FDoL36gxphl0u/4q9tsIGoWxWVpCoij6TD0wHoB S4pZe1xxK+ekmjHTse1+ZMCxSBexxW8ZTmri1LGdDzagZIuEtg6Qc4mlh+7j0JsohgQ6 S7nA== X-Forwarded-Encrypted: i=1; AKwUvBw8MaIP3oztDKqk+ELsux2mIKhYiRNhwwbVfpQt1usu14iQNCa/EgobtBIc6/eMw1q0oSgbIV27YjY2eA==@vger.kernel.org X-Gm-Message-State: AFq9FYIESTlv2uih6vLUGlzqp53Sl7ELLafkeisv9E7/6wsKYaPsPQ9Z KItKV9DjMKwGgAHdN/Ud3G+J2hcxEHIDmejDZPM8jJMlx8KDVYFsnUfwzydiRVOyt4yGMldRU2H iaH9/KSk3DLupUtN2sUBd+Q== 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-btrfs@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