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{ "id": 2229029, "url": "http://patchwork.ozlabs.org/api/1.1/covers/2229029/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-um/cover/cover.1777306795.git.chleroy@kernel.org/", "project": { "id": 60, "url": "http://patchwork.ozlabs.org/api/1.1/projects/60/?format=api", "name": "User-mode Linux Development", "link_name": "linux-um", "list_id": "linux-um.lists.infradead.org", "list_email": "linux-um@lists.infradead.org", "web_url": "", "scm_url": "", "webscm_url": "" }, "msgid": "<cover.1777306795.git.chleroy@kernel.org>", "date": "2026-04-27T17:13:41", "name": "[RFC,v1,0/9] uaccess: Convert small fixed size copy_{to/from}_user() to scoped user access", "submitter": { "id": 92089, "url": "http://patchwork.ozlabs.org/api/1.1/people/92089/?format=api", "name": "Christophe Leroy (CS GROUP)", "email": "chleroy@kernel.org" }, "mbox": "http://patchwork.ozlabs.org/project/linux-um/cover/cover.1777306795.git.chleroy@kernel.org/mbox/", "series": [ { "id": 501693, "url": "http://patchwork.ozlabs.org/api/1.1/series/501693/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-um/list/?series=501693", "date": "2026-04-27T17:13:41", "name": "uaccess: Convert small fixed size copy_{to/from}_user() to scoped user access", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/501693/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/covers/2229029/comments/", "headers": { "Return-Path": "\n <linux-um-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org>", "X-Original-To": "incoming@patchwork.ozlabs.org", "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n secure) header.d=lists.infradead.org header.i=@lists.infradead.org\n header.a=rsa-sha256 header.s=bombadil.20210309 header.b=SnGXeNA6;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=U2+LLE02;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=none (no SPF record) smtp.mailfrom=lists.infradead.org\n (client-ip=2607:7c80:54:3::133; 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a=rsa-sha256; q=dns/txt; c=relaxed/relaxed;\n\td=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help\n\t:List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding:\n\tMIME-Version:Message-ID:Date:Subject:Cc:To:From:Reply-To:Content-Type:\n\tContent-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender:\n\tResent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Owner;\n\tbh=jhUiSYlSjWHWqHISdWgh0N8CQlPC2mYxEyllaCORLRs=; b=SnGXeNA6hSsKown67pUJLD/HGM\n\twsTjjfY/HWJfGy4zJUCCV74CJs5+iBf+AmqaZSqNPLuLb0FvO18x8dKsQdfmHTtrEZG61w0sFPpny\n\tZoc6jjlQBl3JqG68WDzDkdVhxPmdfAndzFexc2lOT3lD/hVi/LWR7s0iV3K08CxMCJgVGEf4pnF4W\n\t5cCov56zgVlxQ+QyR+sF8GrBS39o1ueyla/DEAHbWVG3eR2bBouAjE2P2LxqCcjFdTBxaiFaw16DP\n\trcWFoiFbQOzNm08hvyrcjQWIm9tDjJ6rnTsdrxDDkHXp0ePZEkgj2LiQSq/9fAzEDQ37DK681aWZo\n\tE0VtqsDw==;", "v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org;\n\ts=k20201202; t=1777310218;\n\tbh=Gdo90UdOw5JDNcbBc6CTpgqBoS99tJWdzzhKt47HDkg=;\n\th=From:To:Cc:Subject:Date:From;\n\tb=U2+LLE02v2RJdGrHn64GqYJdP4+hDdO9CRQcGon9U+fg19LBxhX5PBepS5h9HJCqe\n\t szqGGe/Sn0Ja8ufrVfKBRayklpg7ZNqhD3AjlJFyhWTD2cy+E9nyVtxoXvU6RVePwS\n\t nC/EKNFwPrGycTqEuaSwxvd9NLoS3iznsIjTk0KPgTVc+veLovfoR+uQQZvkXu6BEL\n\t XY5HSP+s8CkmcaZnZCCWlv0qtPkuKqPRoos+3EvmYxD3lbF+eVbofOW/u0ribOc9N6\n\t 46gB4iCE7qS4DHXiu+LbPED9AO2rWWkmtG0xffEU92OaQJ+vWiy9PumgjbDE3AiKLE\n\t isfjlgjrnrghg==" ], "From": "\"Christophe Leroy (CS GROUP)\" <chleroy@kernel.org>", "To": "Yury Norov <ynorov@nvidia.com>,\n\tAndrew Morton <akpm@linux-foundation.org>,\n\tLinus Torvalds <torvalds@linux-foundation.org>,\n\tDavid Laight <david.laight.linux@gmail.com>,\n\tThomas Gleixner <tglx@linutronix.de>", "Cc": "\"Christophe Leroy (CS GROUP)\" <chleroy@kernel.org>,\n\tlinux-alpha@vger.kernel.org,\n\tlinux-kernel@vger.kernel.org,\n\tlinux-snps-arc@lists.infradead.org,\n\tlinux-arm-kernel@lists.infradead.org,\n\tlinux-mips@vger.kernel.org,\n\tlinuxppc-dev@lists.ozlabs.org,\n\tkvm@vger.kernel.org,\n\tlinux-riscv@lists.infradead.org,\n\tlinux-s390@vger.kernel.org,\n\tsparclinux@vger.kernel.org,\n\tlinux-um@lists.infradead.org,\n\tdmaengine@vger.kernel.org,\n\tlinux-efi@vger.kernel.org,\n\tlinux-fsi@lists.ozlabs.org,\n\tamd-gfx@lists.freedesktop.org,\n\tdri-devel@lists.freedesktop.org,\n\tintel-gfx@lists.freedesktop.org,\n\tlinux-wpan@vger.kernel.org,\n\tnetdev@vger.kernel.org,\n\tlinux-wireless@vger.kernel.org,\n\tlinux-spi@vger.kernel.org,\n\tlinux-media@vger.kernel.org,\n\tlinux-staging@lists.linux.dev,\n\tlinux-serial@vger.kernel.org,\n\tlinux-usb@vger.kernel.org,\n\txen-devel@lists.xenproject.org,\n\tlinux-fsdevel@vger.kernel.org,\n\tocfs2-devel@lists.linux.dev,\n\tbpf@vger.kernel.org,\n\tkasan-dev@googlegroups.com,\n\tlinux-mm@kvack.org,\n\tlinux-x25@vger.kernel.org,\n\trust-for-linux@vger.kernel.org,\n\tlinux-sound@vger.kernel.org,\n\tsound-open-firmware@alsa-project.org,\n\tlinux-csky@vger.kernel.org,\n\tlinux-hexagon@vger.kernel.org,\n\tloongarch@lists.linux.dev,\n\tlinux-m68k@lists.linux-m68k.org,\n\tlinux-openrisc@vger.kernel.org,\n\tlinux-parisc@vger.kernel.org,\n\tlinux-sh@vger.kernel.org,\n\tlinux-arch@vger.kernel.org", "Subject": "[RFC PATCH v1 0/9] uaccess: Convert small fixed size\n copy_{to/from}_user() to scoped user access", "Date": "Mon, 27 Apr 2026 19:13:41 +0200", "Message-ID": "<cover.1777306795.git.chleroy@kernel.org>", "X-Mailer": "git-send-email 2.49.0", "MIME-Version": "1.0", "X-Developer-Signature": "v=1; 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The original\n message has been attached to this so you can view it or label\n similar future email. If you have any questions, see\n the administrator of that system for details.\n Content preview: A lot of copy_from_user() and copy_to_user() perform copies\n of small fixed size pieces of data between kernel and userspace, and don't\n care about partial copies. copy_from_user() and copy_to_user() are big\n functions\n optimised for copying large amount of data, with cache management, etc ...\n This is often overkill for small copies that could just be inlined inst\n [...] \n Content analysis details: (-2.1 points, 5.0 required)\n pts rule name description\n ---- ----------------------\n --------------------------------------------------\n -0.0 SPF_PASS SPF: sender matches SPF record\n 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record\n -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from\n envelope-from domain\n -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from\n author's\n domain\n -0.1 DKIM_VALID Message has at least one valid DKIM or DK\n signature\n 0.1 DKIM_SIGNED Message has a DKIM or DK signature,\n not necessarily valid\n -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1%\n [score: 0.0000]\n -0.0 DKIMWL_WL_HIGH DKIMwl.org - High trust sender", "X-BeenThere": "linux-um@lists.infradead.org", "X-Mailman-Version": "2.1.34", "Precedence": "list", "List-Id": "<linux-um.lists.infradead.org>", "List-Unsubscribe": "<http://lists.infradead.org/mailman/options/linux-um>,\n <mailto:linux-um-request@lists.infradead.org?subject=unsubscribe>", "List-Archive": "<http://lists.infradead.org/pipermail/linux-um/>", "List-Post": "<mailto:linux-um@lists.infradead.org>", "List-Help": "<mailto:linux-um-request@lists.infradead.org?subject=help>", "List-Subscribe": "<http://lists.infradead.org/mailman/listinfo/linux-um>,\n <mailto:linux-um-request@lists.infradead.org?subject=subscribe>", "Sender": "\"linux-um\" <linux-um-bounces@lists.infradead.org>", "Errors-To": "linux-um-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org" }, "content": "A lot of copy_from_user() and copy_to_user() perform copies of small\nfixed size pieces of data between kernel and userspace, and don't\ncare about partial copies.\n\ncopy_from_user() and copy_to_user() are big functions optimised for\ncopying large amount of data, with cache management, etc ... This is\noften overkill for small copies that could just be inlined instead.\n\nWhat makes things a bit more tricky is that those copy functions\nare designed to handle partial copies in case of page fault. But among\nthe 6000 callers of those functions, only 2% really care about the\nquantity of no-copied data that those functions return. All other ones\nfails as soon as the returned value is not 0, returning -EACCESS.\n\nSo first step in this series is to introduce variants called\ncopy_from_user_partial() and copy_to_user_partial() which will be\ncalled by the 2% users that care about the partial copy, then the\noriginal copy_from_user() and copy_to_user() are changed to return\n-EFAULT when the copy fails.\n\nThen the second step is to implement copy of small fixed-size data\nwith scoped user access instead of calling the arch specific heavy\nuser copy functions.\n\nPatch 5, can be split in different patches for each archicture or\nsubsystem, but let's get a first feedback and agree on the principle.\n\nChristophe Leroy (CS GROUP) (9):\n uaccess: Split check_zeroed_user() out of usercopy.c\n uaccess: Convert INLINE_COPY_{TO/FROM}_USER to kconfig and reduce\n ifdefery\n x86/umip: Be stricter in fixup_umip_exception()\n uaccess: Introduce copy_{to/from}_user_partial()\n uaccess: Switch to copy_{to/from}_user_partial() when relevant\n uaccess: Change copy_{to/from}_user to return -EFAULT\n x86: Add unsafe_copy_from_user()\n arm64: Add unsafe_copy_from_user()\n uaccess: Convert small fixed size copy_{to/from}_user() to scoped user\n access\n\n arch/alpha/Kconfig | 1 +\n arch/alpha/kernel/osf_sys.c | 4 +-\n arch/alpha/kernel/termios.c | 2 +-\n arch/arc/include/asm/uaccess.h | 3 -\n arch/arc/kernel/disasm.c | 2 +-\n arch/arm/include/asm/uaccess.h | 2 -\n arch/arm64/include/asm/gcs.h | 2 +-\n arch/arm64/include/asm/uaccess.h | 30 +++--\n arch/arm64/kernel/signal32.c | 2 +-\n arch/csky/Kconfig | 1 +\n arch/hexagon/include/asm/uaccess.h | 3 -\n arch/loongarch/include/asm/uaccess.h | 3 -\n arch/m68k/include/asm/uaccess.h | 3 -\n arch/microblaze/include/asm/uaccess.h | 2 -\n arch/mips/include/asm/uaccess.h | 3 -\n arch/mips/kernel/rtlx.c | 8 +-\n arch/mips/kernel/vpe.c | 2 +-\n arch/nios2/include/asm/uaccess.h | 2 -\n arch/openrisc/include/asm/uaccess.h | 2 -\n arch/parisc/include/asm/uaccess.h | 3 -\n arch/powerpc/Kconfig | 1 +\n arch/powerpc/kvm/book3s_64_mmu_hv.c | 4 +-\n arch/powerpc/kvm/book3s_64_mmu_radix.c | 4 +-\n arch/powerpc/kvm/book3s_hv.c | 2 +-\n arch/riscv/Kconfig | 1 +\n arch/riscv/kernel/signal.c | 2 +-\n arch/s390/include/asm/idals.h | 8 +-\n arch/s390/include/asm/uaccess.h | 3 -\n arch/sh/include/asm/uaccess.h | 2 -\n arch/sparc/include/asm/uaccess_32.h | 3 -\n arch/sparc/include/asm/uaccess_64.h | 2 -\n arch/sparc/kernel/termios.c | 2 +-\n arch/um/include/asm/uaccess.h | 3 -\n arch/um/kernel/process.c | 2 +-\n arch/x86/Kconfig | 1 +\n arch/x86/include/asm/uaccess.h | 29 ++++-\n arch/x86/kernel/umip.c | 2 +-\n arch/x86/lib/insn-eval.c | 2 +-\n arch/x86/um/signal.c | 2 +-\n arch/xtensa/include/asm/uaccess.h | 2 -\n drivers/android/binder_alloc.c | 2 +-\n drivers/comedi/comedi_fops.c | 4 +-\n drivers/dma/idxd/cdev.c | 2 +-\n drivers/firmware/efi/test/efi_test.c | 2 +-\n drivers/fsi/fsi-scom.c | 2 +-\n .../amd/display/amdgpu_dm/amdgpu_dm_debugfs.c | 2 +-\n drivers/gpu/drm/i915/gt/intel_sseu.c | 4 +-\n drivers/gpu/drm/i915/i915_gem.c | 4 +-\n drivers/hwtracing/intel_th/msu.c | 2 +-\n drivers/misc/ibmvmc.c | 2 +-\n drivers/misc/vmw_vmci/vmci_host.c | 2 +-\n drivers/most/most_cdev.c | 2 +-\n drivers/net/ieee802154/ca8210.c | 4 +-\n drivers/net/wireless/ath/wil6210/debugfs.c | 2 +-\n .../intel/iwlwifi/pcie/gen1_2/trans.c | 2 +-\n drivers/net/wireless/ti/wlcore/debugfs.c | 2 +-\n drivers/ps3/ps3-lpm.c | 2 +-\n drivers/s390/crypto/zcrypt_api.h | 4 +-\n drivers/spi/spidev.c | 2 +-\n .../staging/media/atomisp/pci/atomisp_cmd.c | 8 +-\n drivers/tty/tty_ioctl.c | 14 +--\n drivers/tty/vt/vc_screen.c | 4 +-\n drivers/usb/gadget/function/f_hid.c | 4 +-\n drivers/usb/gadget/function/f_printer.c | 2 +-\n drivers/vfio/vfio_iommu_type1.c | 4 +-\n drivers/xen/xenbus/xenbus_dev_frontend.c | 2 +-\n fs/namespace.c | 2 +-\n fs/ocfs2/dlmfs/dlmfs.c | 2 +-\n fs/proc/base.c | 4 +-\n include/asm-generic/uaccess.h | 2 -\n include/linux/bpfptr.h | 2 +-\n include/linux/sockptr.h | 4 +-\n include/linux/uaccess.h | 107 ++++++++++++++----\n ipc/msg.c | 8 +-\n ipc/sem.c | 8 +-\n ipc/shm.c | 18 +--\n kernel/regset.c | 2 +-\n kernel/sys.c | 4 +-\n lib/Kconfig | 3 +\n lib/Makefile | 4 +-\n lib/kfifo.c | 8 +-\n lib/{usercopy.c => usercheck.c} | 22 ----\n lib/usercopy.c | 66 -----------\n mm/kasan/kasan_test_c.c | 4 +-\n mm/memory.c | 2 +-\n net/x25/af_x25.c | 2 +-\n rust/helpers/uaccess.c | 6 +-\n sound/pci/emu10k1/emufx.c | 4 +-\n sound/pci/rme9652/hdsp.c | 6 +-\n sound/soc/intel/avs/probes.c | 6 +-\n sound/soc/sof/compress.c | 12 +-\n sound/soc/sof/sof-client-probes.c | 6 +-\n 92 files changed, 269 insertions(+), 288 deletions(-)\n copy lib/{usercopy.c => usercheck.c} (73%)" }