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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777310218; bh=Gdo90UdOw5JDNcbBc6CTpgqBoS99tJWdzzhKt47HDkg=; h=From:To:Cc:Subject:Date:From; b=U2+LLE02v2RJdGrHn64GqYJdP4+hDdO9CRQcGon9U+fg19LBxhX5PBepS5h9HJCqe szqGGe/Sn0Ja8ufrVfKBRayklpg7ZNqhD3AjlJFyhWTD2cy+E9nyVtxoXvU6RVePwS nC/EKNFwPrGycTqEuaSwxvd9NLoS3iznsIjTk0KPgTVc+veLovfoR+uQQZvkXu6BEL XY5HSP+s8CkmcaZnZCCWlv0qtPkuKqPRoos+3EvmYxD3lbF+eVbofOW/u0ribOc9N6 46gB4iCE7qS4DHXiu+LbPED9AO2rWWkmtG0xffEU92OaQJ+vWiy9PumgjbDE3AiKLE isfjlgjrnrghg== From: "Christophe Leroy (CS GROUP)" To: Yury Norov , Andrew Morton , Linus Torvalds , David Laight , Thomas Gleixner Cc: "Christophe Leroy (CS GROUP)" , linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, dmaengine@vger.kernel.org, linux-efi@vger.kernel.org, linux-fsi@lists.ozlabs.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-wpan@vger.kernel.org, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, linux-spi@vger.kernel.org, linux-media@vger.kernel.org, linux-staging@lists.linux.dev, linux-serial@vger.kernel.org, linux-usb@vger.kernel.org, xen-devel@lists.xenproject.org, linux-fsdevel@vger.kernel.org, ocfs2-devel@lists.linux.dev, bpf@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-x25@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-sound@vger.kernel.org, sound-open-firmware@alsa-project.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, loongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org, linux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org, linux-sh@vger.kernel.org, linux-arch@vger.kernel.org Subject: [RFC PATCH v1 0/9] uaccess: Convert small fixed size copy_{to/from}_user() to scoped user access Date: Mon, 27 Apr 2026 19:13:41 +0200 Message-ID: X-Mailer: git-send-email 2.49.0 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=7253; i=chleroy@kernel.org; h=from:subject:message-id; bh=Gdo90UdOw5JDNcbBc6CTpgqBoS99tJWdzzhKt47HDkg=; b=owGbwMvMwCV2d0KB2p7V54MZT6slMWS+nxkaMinl/6P42P3bc0Qj3v7nk1G4YbGg/rEse+BPv 7e7BNgWdJSyMIhxMciKKbIc/8+9a0bXl9T8qbv0YeawMoEMYeDiFICJRDExMmwV0vIK89sWnHjX Y4WN3O+gaTyvmP0m2koKTvi9YNORsocM/wPkn2xoM0q8N63lWvLNy/m/speGuG7LLGiQ1I6bVSB dxgQA X-Developer-Key: i=chleroy@kernel.org; a=openpgp; fpr=10FFE6F8B390DE17ACC2632368A92FEB01B8DD78 Content-Transfer-Encoding: 8bit A lot of copy_from_user() and copy_to_user() perform copies of small fixed size pieces of data between kernel and userspace, and don't care about partial copies. copy_from_user() and copy_to_user() are big functions optimised for copying large amount of data, with cache management, etc ... This is often overkill for small copies that could just be inlined instead. What makes things a bit more tricky is that those copy functions are designed to handle partial copies in case of page fault. But among the 6000 callers of those functions, only 2% really care about the quantity of no-copied data that those functions return. All other ones fails as soon as the returned value is not 0, returning -EACCESS. So first step in this series is to introduce variants called copy_from_user_partial() and copy_to_user_partial() which will be called by the 2% users that care about the partial copy, then the original copy_from_user() and copy_to_user() are changed to return -EFAULT when the copy fails. Then the second step is to implement copy of small fixed-size data with scoped user access instead of calling the arch specific heavy user copy functions. Patch 5, can be split in different patches for each archicture or subsystem, but let's get a first feedback and agree on the principle. Christophe Leroy (CS GROUP) (9): uaccess: Split check_zeroed_user() out of usercopy.c uaccess: Convert INLINE_COPY_{TO/FROM}_USER to kconfig and reduce ifdefery x86/umip: Be stricter in fixup_umip_exception() uaccess: Introduce copy_{to/from}_user_partial() uaccess: Switch to copy_{to/from}_user_partial() when relevant uaccess: Change copy_{to/from}_user to return -EFAULT x86: Add unsafe_copy_from_user() arm64: Add unsafe_copy_from_user() uaccess: Convert small fixed size copy_{to/from}_user() to scoped user access arch/alpha/Kconfig | 1 + arch/alpha/kernel/osf_sys.c | 4 +- arch/alpha/kernel/termios.c | 2 +- arch/arc/include/asm/uaccess.h | 3 - arch/arc/kernel/disasm.c | 2 +- arch/arm/include/asm/uaccess.h | 2 - arch/arm64/include/asm/gcs.h | 2 +- arch/arm64/include/asm/uaccess.h | 30 +++-- arch/arm64/kernel/signal32.c | 2 +- arch/csky/Kconfig | 1 + arch/hexagon/include/asm/uaccess.h | 3 - arch/loongarch/include/asm/uaccess.h | 3 - arch/m68k/include/asm/uaccess.h | 3 - arch/microblaze/include/asm/uaccess.h | 2 - arch/mips/include/asm/uaccess.h | 3 - arch/mips/kernel/rtlx.c | 8 +- arch/mips/kernel/vpe.c | 2 +- arch/nios2/include/asm/uaccess.h | 2 - arch/openrisc/include/asm/uaccess.h | 2 - arch/parisc/include/asm/uaccess.h | 3 - arch/powerpc/Kconfig | 1 + arch/powerpc/kvm/book3s_64_mmu_hv.c | 4 +- arch/powerpc/kvm/book3s_64_mmu_radix.c | 4 +- arch/powerpc/kvm/book3s_hv.c | 2 +- arch/riscv/Kconfig | 1 + arch/riscv/kernel/signal.c | 2 +- arch/s390/include/asm/idals.h | 8 +- arch/s390/include/asm/uaccess.h | 3 - arch/sh/include/asm/uaccess.h | 2 - arch/sparc/include/asm/uaccess_32.h | 3 - arch/sparc/include/asm/uaccess_64.h | 2 - arch/sparc/kernel/termios.c | 2 +- arch/um/include/asm/uaccess.h | 3 - arch/um/kernel/process.c | 2 +- arch/x86/Kconfig | 1 + arch/x86/include/asm/uaccess.h | 29 ++++- arch/x86/kernel/umip.c | 2 +- arch/x86/lib/insn-eval.c | 2 +- arch/x86/um/signal.c | 2 +- arch/xtensa/include/asm/uaccess.h | 2 - drivers/android/binder_alloc.c | 2 +- drivers/comedi/comedi_fops.c | 4 +- drivers/dma/idxd/cdev.c | 2 +- drivers/firmware/efi/test/efi_test.c | 2 +- drivers/fsi/fsi-scom.c | 2 +- .../amd/display/amdgpu_dm/amdgpu_dm_debugfs.c | 2 +- drivers/gpu/drm/i915/gt/intel_sseu.c | 4 +- drivers/gpu/drm/i915/i915_gem.c | 4 +- drivers/hwtracing/intel_th/msu.c | 2 +- drivers/misc/ibmvmc.c | 2 +- drivers/misc/vmw_vmci/vmci_host.c | 2 +- drivers/most/most_cdev.c | 2 +- drivers/net/ieee802154/ca8210.c | 4 +- drivers/net/wireless/ath/wil6210/debugfs.c | 2 +- .../intel/iwlwifi/pcie/gen1_2/trans.c | 2 +- drivers/net/wireless/ti/wlcore/debugfs.c | 2 +- drivers/ps3/ps3-lpm.c | 2 +- drivers/s390/crypto/zcrypt_api.h | 4 +- drivers/spi/spidev.c | 2 +- .../staging/media/atomisp/pci/atomisp_cmd.c | 8 +- drivers/tty/tty_ioctl.c | 14 +-- drivers/tty/vt/vc_screen.c | 4 +- drivers/usb/gadget/function/f_hid.c | 4 +- drivers/usb/gadget/function/f_printer.c | 2 +- drivers/vfio/vfio_iommu_type1.c | 4 +- drivers/xen/xenbus/xenbus_dev_frontend.c | 2 +- fs/namespace.c | 2 +- fs/ocfs2/dlmfs/dlmfs.c | 2 +- fs/proc/base.c | 4 +- include/asm-generic/uaccess.h | 2 - include/linux/bpfptr.h | 2 +- include/linux/sockptr.h | 4 +- include/linux/uaccess.h | 107 ++++++++++++++---- ipc/msg.c | 8 +- ipc/sem.c | 8 +- ipc/shm.c | 18 +-- kernel/regset.c | 2 +- kernel/sys.c | 4 +- lib/Kconfig | 3 + lib/Makefile | 4 +- lib/kfifo.c | 8 +- lib/{usercopy.c => usercheck.c} | 22 ---- lib/usercopy.c | 66 ----------- mm/kasan/kasan_test_c.c | 4 +- mm/memory.c | 2 +- net/x25/af_x25.c | 2 +- rust/helpers/uaccess.c | 6 +- sound/pci/emu10k1/emufx.c | 4 +- sound/pci/rme9652/hdsp.c | 6 +- sound/soc/intel/avs/probes.c | 6 +- sound/soc/sof/compress.c | 12 +- sound/soc/sof/sof-client-probes.c | 6 +- 92 files changed, 269 insertions(+), 288 deletions(-) copy lib/{usercopy.c => usercheck.c} (73%) -- 2.49.0