Messages in this thread | | | Date | Mon, 18 Jul 2022 16:10:22 +0100 | Subject | Re: [PATCH -next] riscv: lib: uaccess: fix CSR_STATUS SR_SUM bit | From | Ben Dooks <> |
| |
On 15/06/2022 02:47, Chen Lifu wrote: > 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>
I've not run tested this, but it does look correct
Reviewed-by: Ben Dooks <ben.dooks@codethink.co.uk>
> --- > 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 8c475f4da308..ec486e5369d9 100644 > --- a/arch/riscv/lib/uaccess.S > +++ b/arch/riscv/lib/uaccess.S > @@ -173,11 +173,11 @@ ENTRY(__asm_copy_from_user) > ret > > /* 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) > ENDPROC(__asm_copy_from_user) > EXPORT_SYMBOL(__asm_copy_to_user) > @@ -225,10 +225,10 @@ ENTRY(__clear_user) > j 3b > > /* Exception fixup code */ > 11: > /* Disable access to user memory */ > - csrs CSR_STATUS, t6 > + csrc CSR_STATUS, t6 > mv a0, a1 > ret > ENDPROC(__clear_user) > EXPORT_SYMBOL(__clear_user)
-- Ben Dooks http://www.codethink.co.uk/ Senior Engineer Codethink - Providing Genius
https://www.codethink.co.uk/privacy.html
| |