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Sat, 30 May 2026 18:01:48 -0700 (PDT) Received: from localhost ([212.73.77.104]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-4909cab0e79sm261799535e9.13.2026.05.30.18.01.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 30 May 2026 18:01:48 -0700 (PDT) From: Askar Safin To: linux-fsdevel@vger.kernel.org, Christian Brauner , Alexander Viro , Jan Kara Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, netdev@vger.kernel.org, Linus Torvalds , Matthew Wilcox , Jens Axboe , Christoph Hellwig , David Howells , Andrew Morton , David Hildenbrand , Pedro Falcato , Miklos Szeredi , patches@lists.linux.dev Subject: [PATCH 0/3] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2 Date: Sun, 31 May 2026 01:01:04 +0000 Message-ID: <20260531010107.1953702-1-safinaskar@gmail.com> X-Mailer: git-send-email 2.47.3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: CFCF514000D X-Stat-Signature: 8mfhihtr4ycku6fknwyjth66cp7j9jrw X-HE-Tag: 1780189310-85010 X-HE-Meta: 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 zvtVjDCM 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: This patchset is for VFS. Recently we got a lot of vulnerabilities in splice/vmsplice. Also vmsplice already was source of vulnerabilities in the past: CVE-2020-29374 (see https://lwn.net/Articles/849638/ ). Also vmsplice is problematic for other reasons. Here is what other developers say: Linus Torvalds in 2023: > So I'd personally be perfectly ok with just making vmsplice() be > exactly the same as write, and turn all of vmsplice() into just "it's > a read() if the pipe is open for read, and a write if it's open for > writing". https://lore.kernel.org/all/CAHk-=wgG_2cmHgZwKjydi7=iimyHyN8aessnbM9XQ9ufbaUz9g@mail.gmail.com/ Christoph Hellwig in May 2026: > vmsplice is the worst, as it is one of the few remaining places that > can incorrectly dirty file backed pages without telling the file system > and cause the other problems fixed by a FOLL_PIN conversion, but it is > the only one where we do not have any idea yet how we could convert it > to FOLL_PIN due to the unbounded pin time. https://lore.kernel.org/all/agwFlBKvKytjURDO@infradead.org/ See recent discussion here: https://lore.kernel.org/all/20260516182126.530498-1-pfalcato@suse.de/T/#u For all these reasons I propose to make vmsplice a simple wrapper for preadv2/pwritev2. vmsplice(fd, vec, vlen, vmsplice_flags) will be equivalent to preadv2(fd, vec, vlen, -1, rw_flags) if you have readable pipe and to pwritev2(fd, vec, vlen, -1, rw_flags) if you have writable pipe. SPLICE_F_NONBLOCK is translated to RWF_NOWAIT, all other SPLICE_F_* flags are ignored. There is a small change to handling of NONBLOCK-related flags, see commit messages for details. I tested this patch in Qemu. This patchset was written by me, not by LLMs. Askar Safin (3): tee: fs/splice.c: remove unused parameter "flags" from "link_pipe" vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2 splice: remove PIPE_BUF_FLAG_GIFT fs/fuse/dev.c | 1 - fs/read_write.c | 23 +++++ fs/splice.c | 202 +------------------------------------- include/linux/pipe_fs_i.h | 1 - include/linux/skbuff.h | 4 +- include/linux/splice.h | 2 +- include/linux/syscalls.h | 4 +- 7 files changed, 33 insertions(+), 204 deletions(-) base-commit: e7ae89a0c97ce2b68b0983cd01eda67cf373517d (7.1-rc5) -- 2.47.3