| From | Greg Kroah-Hartman <> | Subject | [PATCH 5.15 025/136] riscv: lib: uaccess: fix CSR_STATUS SR_SUM bit | Date | Mon, 29 Aug 2022 12:58:12 +0200 |
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From: Chen Lifu <chenlifu@huawei.com>
[ Upstream commit c08b4848f596fd95543197463b5162bd7bab2442 ]
Since commit 5d8544e2d007 ("RISC-V: Generic library routines and assembly") and commit ebcbd75e3962 ("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: 5d8544e2d007 ("RISC-V: Generic library routines and assembly") Fixes: ebcbd75e3962 ("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> --- arch/riscv/lib/uaccess.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S index ac34f0026adcd..2c7c1c5026af3 100644 --- a/arch/riscv/lib/uaccess.S +++ b/arch/riscv/lib/uaccess.S @@ -177,7 +177,7 @@ ENTRY(__asm_copy_from_user) /* Exception fixup code */ 10: /* Disable access to user memory */ - csrs CSR_STATUS, t6 + csrc CSR_STATUS, t6 mv a0, t5 ret ENDPROC(__asm_copy_to_user) @@ -229,7 +229,7 @@ ENTRY(__clear_user) /* Exception fixup code */ 11: /* Disable access to user memory */ - csrs CSR_STATUS, t6 + csrc CSR_STATUS, t6 mv a0, a1 ret ENDPROC(__clear_user) -- 2.35.1
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