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[ Upstream commitc08b4848f5] Since commit5d8544e2d0("RISC-V: Generic library routines and assembly") and commitebcbd75e39("riscv: Fix the bug in memory access fixup code"), if __clear_user and __copy_user return from an fixup branch, CSR_STATUS SR_SUM bit will be set, it is a vulnerability, so that S-mode memory accesses to pages that are accessible by U-mode will success. Disable S-mode access to U-mode memory should clear SR_SUM bit. Fixes:5d8544e2d0("RISC-V: Generic library routines and assembly") Fixes:ebcbd75e39("riscv: Fix the bug in memory access fixup code") Signed-off-by: Chen Lifu <chenlifu@huawei.com> Reviewed-by: Ben Dooks <ben.dooks@codethink.co.uk> Link: https://lore.kernel.org/r/20220615014714.1650349-1-chenlifu@huawei.com Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.